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Score: 11.00
Title: A conserved threonine residue in the juxtamembrane domain of the XA21 pattern recognition receptor is critical for kinase autophosphorylation and XA21-mediated immunity .
Author: Chen X Chern M Canlas PE Jiang C Ruan D Cao P Ronald PC
Journal: J Biol Chem Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20118235 Accession (PMID): 20118235
Abstract: Despite the key role that pattern recognition receptors ( PRRs ) play in regulating immunity in plants and animals , the mechanism of activation of the associated non-arginine-aspartate ( non-RD ) kinases is unknown . The rice PRR XA21 recognizes the pathogen-associated molecular pattern , Ax21 ( activator of XA21-mediated immunity ) . Here we show that the XA21 juxtamembrane ( JM ) domain is required for kinase autophosphorylation . Threonine 705 in the XA21 JM domain is essential for XA21 autophosphorylation in vitro and XA21-mediated innate immunity in vivo . The replacement of Thr ( 705 ) by an alanine or glutamic acid abolishes XA21 autophosphorylation and eliminates interactions between XA21 and four XA21-binding proteins in yeast and rice . Although threonine residues analogous to Thr ( 705 ) of XA21 are present in the JM domains of most RD and non-RD plant receptor-like kinases , this residue is not required for autophosphorylation of the Arabidopsis RD RLK BRI1 ( brassinosteroid insensitive 1 ) . The threonine 705 of XA21 is conserved only in the JM domains of plant RLKs but not in those of fly , human , or mouse suggesting distinct regulatory mechanisms . These results contribute to growing knowledge regarding the mechanism by which non-RD RLKs function in plant .
Score: 10.00
Title: Plasma membrane localization and potential endocytosis of constitutively expressed XA21 proteins in transgenic rice .
Author: Chen F Gao MJ Miao YS Yuan YX Wang MY Li Q Mao BZ Jiang LW He ZH
Journal: Mol Plant Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20616165 Accession (PMID): 20616165
Abstract: The rice pattern recognition receptor ( PRR ) XA21 confers race-specific resistance in leaf infection by bacterial blight Xathomonas oryzae pv . oryzae ( Xoo ) , and was shown to be primarily localized to the endoplasmic reticulum ( ER ) when expressed with its native promoter or overexpressed in the protoplast However , whether the protein is still ER-localization in the intact cell when overexpressed remains to be identified . Here , we showed that XA21 , its kinase-dead mutant XA21P ( K736EP ) , and the triple autophosphorylation mutant XA21P ( S686A/T688A/S699A ) GFP fusions were primarily localized to the plasma membrane ( PM ) when overexpressed in the intact transgenic rice cell , and also localized to the ER in the transgenic protoplast The transgenic plants constitutively expressing the wild-type XA21 or its GFP fusion displayed race-specific resistance to Xoo at the adult and seedling stages . XA21 and XA21P ( K736EP ) could be internalized probably via the SCAMP-positive early endosomal compartment in the protoplast , suggesting that XA21 might be endocytosed to initiate resistance responses during pathogen infection . We also established a root infection system and demonstrated that XA21 also mediated race-specific resistance responses to Xoo in the root . Our current study provides an insight into the nature of the XA21-mediated resistance and a practical approach using the root cell system to further dissect the cellular signaling of the PRR during the rice-Xoo interaction .
Score: 10.00
Title: Adaptive evolution of Xa21 homologs in Gramineae .
Author: Tan S Wang D Ding J Tian D Zhang X Yang S
Journal: Genetica Year: 2011 Type: In-Process
Literature: oryza Field: abstract Doc ID: pub22451352 Accession (PMID): 22451352
Abstract: The XA21 protein has broad spectrum resistance against Xanthomonas oryzae pv . oryzae . Although Xa21-mediated immunity is well characterized , little is known about the origin and evolutionary history of this gene in grasses . Therefore , we analyzed all Xa21 gene homologs in eight whole-genome sequenced rice lines , as well as in four gramineous genomes , rice , Brachypodium , sorghum and maize ; using Arabidopsis Xa21 homologs as outgroups , 17 , 7 , 7 and 3 Xa21 homologs were detected in these four grasses , respectively . Synteny and phylogenetic analysis showed that frequent gene translocation , duplication and/or loss , have occurred at Xa21 homologous loci , suggesting that they have undergone or are undergoing rapid generation of copy number variations . Within the rice species , the high level of nucleotide diversity between Xa21-like orthologs showed a strong association with the presence/absence haplotypes , suggesting that the genetic structure of rice lines plays an important role in the variations between these Xa21-like orthologs . Strongly positive selection was detected in the core region of the leucine-rich repeat domains of the Xa21 subclade among the rice lines , indicating that the rapid gene diversification of Xa21 homologs may be a strategy for a given species to adapt to the changing spectrum of species-specific pathogens .
Score: 9.00
Title: Biochemical characterization of the kinase domain of the rice disease resistance receptor-like kinase XA21 .
Author: Liu GZ Pi LY Walker JC Ronald PC Song WY .
Journal: J Biol . Chem . Year: 2002 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11927577 Accession (PMID): 11927577
Abstract: The rice disease resistance gene , Xa21 , encodes a receptor kinase-like protein consisting of leucine-rich repeats in the putative extracellular domain and a serine/threonine kinase in the putative intracellular domain . The putative XA21 kinase domain was expressed as maltose-binding and glutathione S-transferase fusion proteins in Escherichia coli . The fusion proteins are capable of autophosphorylation . Phosphoamino acid analysis of the glutathione S-transferase fusion protein indicates that only serine and threonine residues are phosphorylated . The relative phosphorylation rate of the XA21 kinase against increasing enzyme concentrations follows a first-order rather than second-order kinetics , indicating an intramolecular phosphorylation mechanism . Moreover , the active XA21 kinase can not phosphorylate a kinase-deficient mutant of XA21 kinase . The enzymatic activity of the XA21 kinase in a buffer containing Mn ( 2+ ) is at least 15 times higher than that with Mg ( 2+ ) . The K ( m ) and V ( max ) of XA21 kinase for ATP are 0 . 3 microm and 8 . 4 nmol/mg/min , respectively . Tryptic phosphopeptide mapping reveals that multiple sites on the XA21 kinase are phosphorylated . Finally , our data suggest that the region of XA21 kinase corresponding to the RD kinase activation domain is not phosphorylated , revealing a distinct mode of action compared with the tomato Pto serine/threonine kinase conferring disease resistance .
Score: 9.00
Title: Rice XA21 Binding Protein 3 Is a Ubiquitin Ligase Required for Full Xa21-Mediated Disease Resistance .
Author: Wang YS Pi LY Chen X Chakrabarty PK Jiang J De Leon AL Liu GZ Li L Benny U Oard J Ronald PC Song WY .
Journal: Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub17172358 Accession (PMID): 17172358
Abstract: XA21 is a receptor-like kinase protein in rice ( Oryza sativa ) that confers gene-for-gene resistance to specific races of the causal agent of bacterial blight disease , Xanthomonas oryzae pv oryzae . We identified XA21 binding protein 3 ( XB3 ) , an E3 ubiquitin ligase , as a substrate for the XA21 Ser and Thr kinase . The interaction between XB3 and the kinase domain of XA21 has been shown in yeast and in vitro , and the physical association between XB3 and XA21 in vivo has also been confirmed by coimmunoprecipitation assays . XB3 contains an ankyrin repeat domain and a RING finger motif that is sufficient for its interaction with the kinase domain of XA21 and for its E3 ubiquitin ligase activity , respectively . Transgenic plants with reduced expression of the Xb3 gene are compromised in resistance to the avirulent race of X oryzae pv oryzae . Furthermore , reduced levels of Xb3 lead to decreased levels of the XA21 protein . These results indicate that Xb3 is necessary for full accumulation of the XA21 protein and for Xa21-mediated resistance .
Score: 9.00
Title: Rice XB15 , a protein phosphatase 2C , negatively regulates cell death and XA21-mediated innate immunity .
Author: Park CJ Peng Y Chen X Dardick C Ruan D Bart R Canlas PE Ronald PC
Journal: PLoS Biol Year: 2008 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub18817453 Accession (PMID): 18817453
Abstract: Perception of extracellular signals by cell surface receptors is of central importance to eukaryotic development and immunity . Kinases that are associated with the receptors or are part of the receptors themselves modulate signaling through phosphorylation events . The rice ( Oryza sativa L ) XA21 receptor kinase is a key recognition and signaling determinant in the innate immune response . A yeast two-hybrid screen using the intracellular portion of XA21 , including the juxtamembrane ( JM ) and kinase domain as bait , identified a protein phosphatase 2C ( PP2C ) , called XA21 binding protein 15 ( XB15 ) . The interaction of XA21 and XB15 was confirmed in vitro and in vivo by glutathione-S-transferase ( GST ) pull-down and co-immunoprecipitation assays , respectively . XB15 fusion proteins purified from Escherichia coli and from transgenic rice carry PP2C activity . Autophosphorylated XA21 can be dephosphorylated by XB15 in a temporal and dosage-dependent manner . A serine residue in the XA21 JM domain is required for XB15 binding . Xb15 mutants display a severe cell death phenotype , induction of pathogenesis-related genes , and enhanced XA21-mediated resistance . Overexpression of Xb15 in an XA21 rice line compromises resistance to the bacterial pathogen Xanthomonas oryzae pv . oryzae . These results demonstrate that Xb15 encodes a PP2C that negatively regulates the XA21-mediated innate immune response .
Score: 9.00
Title: Xa21D encodes a receptor-like molecule with a leucine-rich repeat domain that determines race-specific recognition and is subject to adaptive evolution .
Author: Wang GL Ruan DL Song WY Sideris S Chen L Pi LY Zhang S Zhang Z Fauquet C Gaut BS Whalen MC Ronald PC .
Journal: Plant Cell Year: 1998 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub9596635 Accession (PMID): 9596635
Abstract: The rice Xa21 gene confers resistance to Xanthomonas oryzae pv oryzae in a race-specific manner . Analysis of the inheritance patterns and resistance spectra of transgenic plants carrying six Xa21 gene family members indicated that one member , designated Xa21D , displayed a resistance spectrum identical to that observed for Xa21 but conferred only partial resistance . Xa21D encodes a receptor-like protein carrying leucine-rich repeat ( LRR ) motifs in the presumed extracellular domain . The Xa21D transcript terminates shortly after the stop codon introduced by the retrotransposon Retrofit . Comparison of nucleotide substitutions in the LRR coding regions of Xa21 and Xa21D provided evidence of adaptive selection . Both functional and evolutionary evidence indicates that the Xa21D LRR domain controls race-specific pathogen recognition .
Score: 8.00
Title: Genetic and physical analysis of the rice bacterial blight disease resistance locus , Xa21 .
Author: Ronald PC Albano B Tabien R Abenes L Wu KS McCouch S Tanksley SD .
Journal: Mol . Gen . Genet . Year: 1992 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub1362973 Accession (PMID): 1362973
Abstract: Nearly isogenic lines ( NILs ) of rice ( Oryza sativa ) differing at a locus conferring resistance to the pathogen Xanthomonas oryzae pv . oryzae were surveyed with 123 DNA markers and 985 random primers using restriction fragment length plymorphism ( RFLP ) and random amplified polymorphic DNA ( RAPD ) analysis . One chromosome 11 marker ( RG103 ) detected polymorphism between the NILs that cosegregated with Xa21 . All other chromosome 11 DNA markers tested were monomorphic between the NILs , localizing the Xa21 introgressed region to an 8 . 3 cM interval on chromosome 11 . Furthermore , we identified two polymerase chain reaction ( PCR ) products ( RAPD2148 and RAPD818 ) that detected polymorphisms between the NILs . Genomic sequences hybridizing with RAPD818 , RAPD248 and RG103 were duplicated specifically in the Xa21 NIL . All three markers cosegregated with the resistance locus , Xa21 , in a F2 population of 386 progeny . Based on the frequency with which we recovered polymorphic Xa21-linked markers , we estimated the physical size of the introgressed region to be approximately 800 kb . This estimation was supported by physical mapping ( using pulsed field gel electrophoresis ) of the sequences hybridizing with the three Xa21-linked DNA markers . The results showed that the three Xa21-linked markers are physically close to each other , with one copy of the RAPD818 sequences located within 60 kb of RAPD248 and the other copy within 270 kb of RG103 . None of the enzymes tested generated a DNA fragment that hybridized with all three of the markers indicating that the introgressed region containing the resistance locus Xa21 is probably larger than 270 kb .
Score: 8.00
Title: Isolation and characterization of rice mutants compromised in Xa21-mediated resistance to X oryzae pv . oryzae .
Author: Wang GL Wu C Zeng L He C Baraoidan M de Assis Goes da Silva F Williams CE Ronald PC Leung H
Journal: Theor . Appl . Genet . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub14523518 Accession (PMID): 14523518
Abstract: The rice gene , Xa21 , confers resistance to diverse races of Xanthomonas oryzae pv . oryzae ( Xoo ) and encodes a receptor-like kinase with leucine-rich repeats in the extra-cellular domain . To identify genes essential for the function of the Xa21 gene , 4 , 500 IRBB21 ( Xa21 isogenic line in IR24 background ) mutants , induced by diepoxybutane and fast neutrons , were screened against Philippine race six ( PR6 ) Xoo for a change from resistance to susceptibility . From two greenhouse screens , 23 mutants were identified that had changed from resistant to fully ( 6 ) or partially ( 17 ) susceptible to PR6 . All fully susceptible mutants carried rearrangements at the Xa21 locus as detected by PCR and Southern hybridization . For the partially susceptible mutants , no changes were detected at the Xa21 locus based on Southern and PCR analyses . However , two of these mutants were confirmed via genetic analysis to have mutations at the Xa21 locus . Partially susceptible mutants exhibited variation in level of susceptibility to different Xoo strains , suggesting that they may carry different mutations required for the Xa21-mediated resistance . The mutants identified in this study provide useful materials for dissecting the Xa21-mediated resistance pathway in rice .
Score: 8.00
Title: Analysis of T-DNA Xa21 loci and bacterial blight resistance effects of the transgene Xa21 in transgenic rice .
Author: Zhai W Chen C Zhu X Chen X Zhang D Li X Zhu L
Journal: Theor . Appl . Genet . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15088086 Accession (PMID): 15088086
Abstract: The genetic loci and phenotypic effects of the transgene Xa21 , a bacterial blight ( BB ) resistance gene cloned from rice , were investigated in transgenic rice produced through an Agrobacterium-mediated transformation system . The flanking sequences of integrated T-DNAs were isolated from Xa21 transgenic rice lines using thermal asymmetric interlaced PCR . Based on the analysis of 24 T-DNA Xa21 flanking sequences , T-DNA loci in rice could be classified into three types : the typical T-DNA integration with the definite left and right borders , the T-DNA integration linked with the adjacent vector backbone sequences and the T-DNA integration involved in a complicated recombination in the flanking sequences . The T-DNA integration in rice was similar to that in dicotyledonous genomes but was significantly different from the integration produced through direct DNA transformation approaches . All three types of integrated transgene Xa21 could be stably inherited and expressed the BB resistance through derived generations in their respective transgenic lines . The flanking sequences of the typical T-DNA integration consisted of actual rice genomic DNA and could be used as probes to locate the transgene on the rice genetic map . A total of 15 different rice T-DNA flanking sequences were identified . They displayed restriction fragment length polymorphisms ( RFLPs ) between two rice varieties , ZYQ8 and JX17 , and were mapped on rice chromosomes 1 , 3 , 4 , 5 , 7 , 9 , 10 , 11 and 12 , respectively , by using a double haploid population derived from a cross between ZYQ8 and JX17 . The blast search and homology comparison of the rice T-DNA flanking sequences with the rice chromosome-anchored sequence database confirmed the RFLP mapping results . On the basis of genetic mapping of the T-DNA Xa21 loci , the BB resistance effects of the transgene Xa21 at different chromosome locations were investigated using homozygous transgenic lines with only one copy of the transgene . Among the transgenic lines , no obvious position effects of the transgene Xa21 were observed . In addition , the BB resistance levels of the Xa21 transgenic plants with different transgene copy numbers and on different genetic backgrounds were also investigated . It was observed that genetic background ( or genome ) effects were more obvious than dosage effects and position effects on the BB resistance level of the transgenic plants .
Score: 8.00
Title: Elucidation of XA21-mediated innate immunity .
Author: Park CJ Han SW Chen X Ronald PC
Journal: Cell Microbiol Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20590657 Accession (PMID): 20590657
Abstract: In the early 1970s , the Xa21 gene from the wild rice species Oryza longistaminata drew attention of rice breeders because of its broad-spectrum resistance to diverse strains of a serious bacterial disease of rice in Asia and Africa , called bacterial blight disease , caused by the Gram-negative bacterium , Xanthomonas oryzae pv . oryzae ( Xoo ) . In 1995 , we isolated the gene controlling this resistance and in 2009 demonstrated that XA21 recognizes a highly conserved peptide , called Ax21 ( activator of XA21-mediated immunity ) . Tyrosine sulfation of Ax21 is required for recognition by rice XA21 . A decade of genetic , molecular and biochemical studies have uncovered key components of the XA21-mediated signalling cascade . Ax21 recognition by XA21 at the cell surface induces phosphorylation-mediated events , which are predicted to alter subcellular localization and/or DNA-binding activity of a WRKY family of transcription factors . Because XA21 is representative of the large number of predicted pattern recognition receptors ( PRRs ) in rice ( n = 328 ) , Arabidopsis ( n = 35 ) and other plant species , further characterization of XA21-mediated signalling pathways will contribute to elucidation of these important defence responses .
Score: 7.00
Title: Short communication : developmental control of Xa21-mediated disease resistance in rice .
Author: Century KS Lagman RA Adkisson M Morlan J Tobias R Schwartz K Smith A Love J Ronald PC Whalen MC .
Journal: Plant J Year: 1999 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub10571882 Accession (PMID): 10571882
Abstract: The rice resistance gene Xa21 confers resistance against the bacterial pathogen Xanthomonas oryzae pv . oryzae ( Xoo ) . The molecular genetic mechanism controlling the integration of the Xa21-mediated disease resistance response with the developmental program in rice is under study in this model system . Reproducible means of infecting plants at certain developmental stages were designed based on the timing of full expansion of the leaf . Xa21-resistance progressively increases from the susceptible juvenile leaf 2 stage through later stages , with 100% resistance at the adult leaf 9/10 stage . We found that Xa21 expression is independent of plant developmental stage , infection with Xoo , or wounding . Expression of the Xa21 gene transcript is not correlated with expression of Xa21 disease resistance indicating that the developmental regulation of Xa21-resistance is either controlled post-transcriptionally or by other factors .
Score: 7.00
Title: The autophosphorylated Ser686 , Thr688 , and Ser689 residues in the intracellular juxtamembrane domain of XA21 are implicated in stability control of rice receptor-like kinase .
Author: Xu WH Wang YS Liu GZ Chen X Tinjuangjun P Pi LY Song WY .
Journal: Plant J Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub16460508 Accession (PMID): 16460508
Abstract: The rice gene Xa21 confers resistance against Xanthomonas oryzae pv . oryzae ( Xoo ) . Xa21 encodes a receptor-like kinase ( XA21 ) . We demonstrate that XA21 autophosphorylates residues Ser686 , Thr688 and Ser689 in vitro . Substitution of these residues with alanines did not affect the autophosphorylation function of this kinase , but specifically destabilized the resistance protein in vitro and in vivo . Plants carrying these same substitutions in XA21 were compromised in their resistance to the normally avirulent Xoo Philippine race 6 . Additionally , we show that wild-type XA21 and the kinase-dead mutant with the invariable Lys736 residue mutated to glutamic acid were also proteolytically degraded in protein extracts . Finally , we show a correlation between the in vitro degradation and in vivo instability of the proteins . We propose that autophosphorylation of Ser686 , Thr688 and Ser689 functions to stabilize XA21 against the developmentally controlled proteolytic activity .
Score: 7.00
Title: Ectopic expression of rice Xa21 overcomes developmentally controlled resistance to Xanthomonas oryzae pv . oryzae .
Author: Park CJ Lee SW Chern M Sharma R Canlas PE Song MY Jeon JS Ronald PC
Journal: Plant Sci Year: 2010 Type: In-Data-Review
Literature: oryza Field: abstract Doc ID: pub21076626 Accession (PMID): 21076626
Abstract: Recognition of pathogen-associated molecular patterns ( PAMPs ) by pattern recognition receptors ( PRRs ) activates the innate immune response . The rice PRR , XA21 , confers robust resistance at adult stages to most strains of the bacterial pathogen Xanthomonas oryzae pv . oryzae ( Xoo ) . Seedlings are still easily infected by Xoo , causing severe yield losses . Here we report that Xa21 is induced by Xoo infection and that ectopic expression of Xa21 confers resistance at three leaf stage ( three-week-old ) , overcoming the developmental limitation of XA21-mediated resistance . Ectopic expression of Xa21 also up-regulates a larger set of defense-related genes as compared to Xa21 driven by the native promoter . These results indicate that altered regulation of Xa21 expression is useful for developing enhanced resistance to Xoo at multiple developmental stages .
Score: 6.00
Title: [ Accelerated improvement of bacterial blight resistance of Shuhui527 using molecular marker-assisted selection ]
Author: Huang TY Li SG Wang YP Li HY .
Journal: Sheng Wu Gong Cheng Xue Bao Year: 2003 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15966313 Accession (PMID): 15966313
Abstract: Shuhui527 is a promising restorer line bred by Rice Research Institute of Sichuan Agricultural University in recent years . However , this line is susceptible to Bacterial Blight ( BB ) , which limits its use . The IRBB60 , from the International Rice Research Institute ( IRRI ) , contains dominant genes Xa21 and Xa4 conferring resistance to BB . The objective of this study is to improve the BB resistance of Shuhui527 by introgressing Xa21 and Xa4 , the two broad-spectrum BB resistance genes , into Shuhui527 with IRBB60 as the donor , pTA248 and MP12 , linking tightly with Xa21 and Xa4 respectively as DNA markers . BC1 F1 progenies of ( Shuhui527 x IRBB60 ) , containing Xa21 and Xa4 identified using PCR screening and with agronomic traits including plant type , grain type and days to heading etc similar to those of Shuhui527 , were subsequently backcrossed to Shuhui527 and self-pollinated to generate BC2 F1 and BC1 F2 . The BC3 F1 and BC3 F2 were subsequently developed using the same approach . Among the 20 BC3 F2 plants , homozygous Xa21 and Xa4 , 10 plants were the most similar to Shuhui527 in the agronomic traits , and were screened using 120 pairs SSR and 100 pairs RAPD markers . Based on the results of the background screening and the performance of the agronomic traits , 5 plants were identified as improved-Shuhui527 and designated as 527R-5 , 527R-6 , 527R-8 , 527R-9 and 527R-10 . The improved- Shuhui527 lines expressed high resistance to Xanthomonas oryzae pv . oryzae ( Xoo ) stains C I - C VII , P1 and P6 . The evaluation of the polymorphisms and selection accuracies of pTA248 and MP12 demonstrated that the polymorphisms of the two markers were obvious and co-dominant and the accuracies were more than 97% and 83% respectively , indicating the two markers are good for Xa21 and Xa4 in Molecular Marker-assisted Selection .
Score: 6.00
Title: Epigenetic inheritance in rice plants .
Author: Akimoto K Katakami H Kim HJ Ogawa E Sano CM Wada Y Sano H
Journal: Ann Bot ( Lond ) Year: 2007 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub17576658 Accession (PMID): 17576658
Abstract: BACKGROUND AND AIMS : Epigenetics is defined as mechanisms that regulate gene expression without base sequence alteration . One molecular basis is considered to be DNA cytosine methylation , which reversibly modifies DNA or chromatin structures . Although its correlation with epigenetic inheritance over generations has been circumstantially shown , evidence at the gene level has been limited . The present study aims to find genes whose methylation status directly correlates with inheritance of phenotypic changes . METHODS : DNA methylation in vivo was artificially reduced by treating rice ( Oryza sativa ssp . japonica ) seeds with 5-azadeoxycytidine , and the progeny were cultivated in the field for > 10 years . Genomic regions with changed methylation status were screened by the methylation-sensitive amplified polymorphysm ( MSAP ) method , and cytosine methylation was directly scanned by the bisulfite mapping method . Pathogen infection with Xanthomonas oryzae pv . oryzae , race PR2 was performed by the scissors-dip method on mature leaf blades . KEY RESULTS : The majority of seedlings were lethal , but some survived to maturity . One line designated as Line-2 showed a clear marker phenotype of dwarfism , which was stably inherited by the progeny over nine generations . MSAP screening identified six fragments , among which two were further characterized by DNA blot hybridization and direct methylation mapping . One clone encoding a retrotransposon gag-pol polyprotein showed a complete erasure of 5-methylcytosines in Line-2 , but neither translocation nor expression of this region was detectable . The other clone encoded an Xa21-like protein , Xa21G . In wild-type plants , all cytosines were methylated within the promoter region , whereas in Line-2 , corresponding methylation was completely erased throughout generations . Expression of Xa21G was not detectable in wild type but was constitutive in Line-2 . When infected with X oryzae pv . oryzae , against which Xa21 confers resistance in a gene-for-gene manner , the progeny of Line-2 were apparently resistant while the wild type was highly susceptible without Xa21G expression . CONCLUSIONS : These results indicated that demethylation was selective in Line-2 , and that promoter demethylation abolished the constitutive silencing of Xa21G due to hypermethylation , resulting in acquisition of disease resistance . Both hypomethylation and resistant trait were stably inherited . This is a clear example of epigenetic inheritance , and supports the idea of Lamarckian inheritance which suggested acquired traits to be heritable .
Score: 6.00
Title: [ Expression and autophosphorylation analysis of XA21 and PI-D2 protein kinases in Saccharomyces cerevisiae ]
Author: Wang SL Li LY Shang JJ Wang J Liu GZ
Journal: Wei Sheng Wu Xue Bao Year: 2007 Type: In-Process
Literature: oryza Field: abstract Doc ID: pub18271255 Accession (PMID): 18271255
Abstract: Rice bacterial blight and blast are the most crucial rice disease . Xa21 confers resistance to bacterial blight , while Pi-d2 confers resistance to rice blast Both Xa21 and Pi-d2 encode receptor kinase-like proteins . Biochemical properties of XA21 kinase expressed in bacterial were characterized in our previous report . In this study , both XA21 and PI-D2 kinase domain were PCR amplified and cloned into yeast expression vector pEGH via recombinational cloning strategy , kinase proteins expressed in eukaryotic yeast system was purified and autophosphorylation assay was carried out . The results indicated that XA21 and PI-D2 protein can be detected by SDS-PAGE and showed expected molecular weight . Autophosphorylation assay indicated that yeast expressed XA21 and PI-D2 were active when incubated with P32 labelled ATP . The experiment provided basic materials for biochemical prosperity analysis , protein-protein interaction and substrate screening research .
Score: 6.00
Title: Dissection of the factors affecting development-controlled and race-specific disease resistance conferred by leucine-rich repeat receptor kinase-type R genes in rice .
Author: Zhao J Fu J Li X Xu C Wang S
Journal: Theor Appl Genet Year: 2009 Type: Publisher
Literature: oryza Field: abstract Doc ID: pub19390838 Accession (PMID): 19390838
Abstract: Development-controlled resistance and resistance specificity frequently restrict the application of a disease resistance ( R ) gene in crop breeding programs . Xa3/Xa26 and Xa21 , encoding leucine-rich repeat ( LRR ) -kinase type plasma membrane proteins , mediate race-specific resistance to Xanthomonas oryzae pv . oryzae ( Xoo ) , which causes bacterial blight , one of the most devastating rice diseases . Plants carrying Xa3/Xa26 and plants carrying Xa21 have different resistance spectra and the functions of the two R genes are regulated by developmental stage . Four chimeric genes encoding proteins consisting of different parts of XA3/XA26 and XA21 were constructed by domain swapping and transformed into a susceptible rice variety . The resistance spectra and development-regulated resistance of the transgenic plants carrying Xa3/Xa26 , Xa21 , or chimeric gene to different Xoo strains were analyzed in the same genetic background . The results suggest that the gradually increased expression of Xa3/Xa26 and Xa21 plays an important role in the progressively enhanced Xoo resistance during rice development . In addition , the LRR domains of XA3/XA26 and XA21 are important determinants of race-specific recognition during rice-Xoo interaction , but juxtamembrane regions of the two R proteins also appear to contribute to resistance specificity .
Score: 6.00
Title: Overexpression of the endoplasmic reticulum chaperone BiP3 regulates XA21-mediated innate immunity in rice .
Author: Park CJ Bart R Chern M Canlas PE Bai W Ronald PC
Journal: PLoS One Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20174657 Accession (PMID): 20174657
Abstract: Recognition of pathogen-associated molecular patterns by pattern recognition receptors ( PRRs ) activates the innate immune response . Although PRR-mediated signaling events are critical to the survival of plants and animals , secretion and localization of PRRs have not yet been clearly elucidated . Here we report the in vivo interaction of the endoplasmic reticulum ( ER ) chaperone BiP3 with the rice XA21 PRR , which confers resistance to the Gram negative bacterium , Xanthomonas oryzae pv . oryzae ( Xoo ) . We show that XA21 is glycosylated and is primarily localized to the ER and also to the plasma membrane ( PM ) . In BiP3-overexpressing rice plants , XA21-mediated immunity is compromised , XA21 stability is significantly decreased , and XA21 proteolytic cleavage is inhibited . BiP3 overexpression does not affect the general rice defense response , cell death or brassinolide-induced responses . These results indicate that BiP3 regulates XA21 protein stability and processing and that this regulation is critical for resistance to Xoo .
Score: 5.00
Title: [ Generation of selectable marker-free and vector backbone sequence-free Xa21 transgenic rice ]
Author: Xia ZH Li XB Chen CY Fan HK Jiang GH Zhu LH Zhai WX .
Journal: Sheng Wu Gong Cheng Xue Bao Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub16607944 Accession (PMID): 16607944
Abstract: The dominant gene Xa21 with broad-spectrum and high resistance to Xanthomonas oryzae pv . oryzae ( Xoo ) was transferred into C418 , an important restorer line of japonica hybrid rice in China using double right-border ( DRB ) T-DNA binary vector through Agrobacterium-mediated transformation . 17 transgenic lines were Xa21-positive with high resistance to the race P6 of Xoo through PCR analysis and resistance identification , among the total 27 independent primary transformants ( T0 ) obtained . The subsequent analysis of the T1 progenies of these 17 T0 lines through PCR-assisted selection and resistance investigation showed that four Xa21 transgenic T0 lines could produce selectable marker-free ( SMF ) progenies . The frequency of primary transformants producing SMF progenies was 15% . In addition , PCR analysis also revealed these SMF progenies did not contain vector backbone sequence , and they were named as SMF and vector backbone sequence-free ( SMF-VBSF ) Xa21 transgenic plants . The further molecular and phenotypic analysis of the T2 and T3 progenies testified the homozygous SMF-VBSF Xa21 transgenic plants were obtained with high resistance to Xoo .
Score: 5.00
Title: [ Advances of rice bacterial blight disease resistance gene Xa21 ]
Author: Bai H Li LY Liu GZ .
Journal: Yi Chuan Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub16818441 Accession (PMID): 16818441
Abstract: Gene Xa21 is the first disease resistance gene cloned from rice ( Oryza sativa L ) , which encodes a receptor-like kinase and confers broad spectrum resistance against Xanthomonas oryzae pv . oryzae ( Xoo ) . In this paper , the discovery , mapping and cloning of Xa21 were reviewed briefly . The molecular mechanism of resistance and its breeding application , including biochemical properties of the kinase domain of XA21 , AvrXa21 identification , the disease resistance pathway mediated by Xa21 , and the mechanism of disease resistance were summarized . Future perspective on Xa21-related research is also discussed .
Score: 5.00
Title: An ATPase promotes autophosphorylation of the pattern recognition receptor XA21 and inhibits XA21-mediated immunity .
Author: Chen X Chern M Canlas PE Ruan D Jiang C Ronald PC
Journal: Proc Natl Acad Sci U S A Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20385831 Accession (PMID): 20385831
Abstract: Cell-surface pattern recognition receptors ( PRRs ) are key components of the innate immune response in animals and plants . These receptors typically carry or associate with non-RD kinases to control early events of innate immunity signaling . Despite their importance , the mode of regulation of PRRs is largely unknown . Here we show that the rice PRR , XA21 , interacts with XA21 binding protein 24 ( XB24 ) , a previously undescribed ATPase . XB24 promotes autophosphorylation of XA21 through its ATPase activity . Rice lines silenced for Xb24 display enhanced XA21-mediated immunity , whereas rice lines overexpressing XB24 are compromised for immunity . XB24 ATPase enzyme activity is required for XB24 function . XA21 is degraded in the presence of the pathogen-associated molecular pattern Ax21 when XB24 is overexpressed . These results demonstrate a function for this large class of broadly conserved ATPases in PRR-mediated immunity .
Score: 5.00
Title: Transcriptional characteristics of Xa21-mediated defense responses in rice .
Author: Gan Q Bai H Zhao X Tao Y Zeng H Han Y Song W Zhu L Liu G
Journal: J Integr Plant Biol Year: 2011 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub21324061 Accession (PMID): 21324061
Abstract: Bacterial blight , caused by Xanthomonas oryzae pv . oryzae ( Xoo ) , is the most destructive bacterial disease of rice . The cloned rice gene Xa21 confers resistance to a broad spectrum of Xoo races . To identify genes involved in Xa21-mediated immunity , a whole-genome oligonucleotide microarray of rice was used to profile the expression of rice genes between incompatible interactions and mock treatments at 0 , 4 , 8 , 24 , 72 and 120 h post inoculation ( hpi ) or between incompatible and compatible interactions at 4 hpi , respectively . A total of 441 differentially expressed genes , designated as XDGs ( Xa21 mediated differentially expressed genes ) , were identified . Based on their functional annotations , the XDGs were assigned to 14 categories , including defense-related , signaling , transcriptional regulators . Most of the defense-related genes belonged to the pathogenesis-related gene family , which was induced dramatically at 72 and 120 hpi . Interestingly , most signaling and transcriptional regulator genes were downregulated at 4 and 8 hpi , suggesting that negative regulation of cellular signaling may play a role in the Xa21-mediated defense response . Comparison of expression profiles between Xa21 and other R gene-mediated defense systems revealed interesting common responses . Representative XDGs with supporting evidences were also discussed .
Score: 5.00
Title: Cleavage and nuclear localization of the rice XA21 immune receptor .
Author: Park CJ Ronald PC
Journal: Nat Commun Year: 2012 Type: In-Data-Review
Literature: oryza Field: abstract Doc ID: pub22735448 Accession (PMID): 22735448
Abstract: Plants and animals carry specific receptors that recognize invading pathogens and respond by activating an immune response . The rice XA21 receptor confers broad-spectrum immunity to the Gram-negative bacterial pathogen , Xanthomonas oryzae pv . oryzae upon recognition of a small protein , Ax21 , that is conserved in all Xanthomonas species and related genera . Here we demonstrate that XA21 is cleaved to release the intracellular kinase domain and that this intracellular domain carries a functional nuclear localization sequence . Bimolecular fluorescence complementation assays indicate that the XA21 intracellular domain interacts with the OsWRKY62 transcriptional regulator exclusively in the nucleus of rice protoplasts . In vivo cleavage of XA21 and translocalization of the intracellular kinase domain to the nucleus is required for the XA21-mediated immune response . These results suggest a new model for immune receptor function : on receptor recognition of conserved microbial signatures , the associated kinase translocates to the nucleus where it directly interacts with transcriptional regulators .
Score: 4.00
Title: [ Genetic mapping of T-DNA integration sites in Xa21 transgenic rice ]
Author: Zhu XF Chen XW Li XB Qian Q Huang DN Zhu LH Zhai WX .
Journal: Yi Chuan Xue Bao Year: 2002 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub12561472 Accession (PMID): 12561472
Abstract: The transformation mediated by Agrobacterium has been successfully applied to rice in recent years . In the previous research we have transferred the Xa21 gene into five rice varieties of China , using Agrobacterium-mediated trasformation . In this study , T-DNA flanking sequences of Xa21 transgenic rice lines were obtained by using thermal asymmetric interlaced PCR ( TAIL-PCR ) . The flanking sequences which are actual rice DNA were identified and located on molecular linkage map developed from a ZYQ8/JX17 double haploid ( DH ) population . A total of 22 T-DNA flanking rice sequences were isolated . Nineteen of them displayed RFLPs between the two parents , ZYQ8 and JX17 , and were mapped on the rice chromosomes , 3 , 4 , 7 , 9 , 10 , 11 and 12 , respectively . The genetic mapping of T-DNA integration sites in Xa21 transgenic rice will benefit the study of position effect and stable inheritance of the transgene Xa21 .
Score: 4.00
Title: Cloning and characterization of receptor kinase class disease resistance gene candidates in Citrus .
Author: Deng Z Gmitter FG .
Journal: Theor . Appl . Genet . Year: 2003 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub13679986 Accession (PMID): 13679986
Abstract: The rice gene Xa21 represents a unique class of plant disease resistance ( R ) genes with distinct protein structure and broad-spectrum specificity ; few sequences or genes of this class have been cloned and characterized in other plant species . Degenerate primers were designed from the conserved motifs in the kinase domains of Xa21 and tomato Pto , and used in PCR amplification to identify this class of resistance gene candidate ( RGC ) sequences from citrus for future evaluation of possible association with citrus canker resistance . Twenty-nine RGC sequences highly similar to the kinase domain of Xa21 ( 55%-60% amino-acid identity ) were cloned and characterized . To facilitate recovery of full-length gene structures and to overcome RGC mapping limitations , large-insert genomic clones ( BACs ) were identified , fingerprinted and assembled into contigs . Southern hybridization revealed the presence of 1-3 copies of receptor-like kinase sequences ( ie , clustering ) in each BAC . Some of these sequences were sampled by PCR amplification and direct sequencing . Twenty-three sequences were thus obtained and classified into five groups and eight subgroups , which indicates the possibility of enhancing RGC sequence diversity from BACs . A primer-walking strategy was employed to derive full-length gene structures from two BAC clones ; both sequences 17o6RLK and 26m19RLK contained all the features of the rice Xa21 protein , including a signal peptide , the same number of leucine-rich-repeats , and transmembrane and kinase domains . These results demonstrate that PCR amplification with appropriately designed degenerate primers is an efficient approach for cloning receptor-like kinase class RGCs . Utilization of BAC clones can facilitate this approach in multiple ways by improving sequence diversity , providing full-length genes , and assisting in understanding gene structures and distribution .
Score: 4.00
Title: [ Isolation and Sequence Analysis of the Xa21 Gene Wxon II Homologus from Different Species of Wild Rice in Yunnan . ]
Author: Qian J Cheng ZQ Yang MZ Liu JM Wu CJ Huang XQ .
Journal: Yi Chuan Year: 2005 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15985401 Accession (PMID): 15985401
Abstract: The Xa21 gene previously cloned from the wild rice species Oryzae longistaminata confers broad-spectrum resistance to rice leaf blight caused by different strains of Xanthomonas oryzae pv . oryzae . Here we attempted to determine the existence of Xa21 homologs in other wild rice species and rice cultivars and the sequence differences between the homologs . We synthesized specific primers based on the reported Xa21 sequence to amplify homologs of the gene exon II from several rice cultivars and three wild rice species in Yunnan Province , China . The fragments cloned from various types of O rufipogon Griff from Jinghong and Yuanjiang , Yunnan Province , were highly homologous to the reported Xa21 gene exon II . However , the fragment was not found in O officinalis Wall . and O meyeriana Baill . Sequence analysis suggested that differences in nucleotides were located randomly in the fragments we cloned .
Score: 4.00
Title: [ Application of competitive PCR for screening selectable marker-free Xa21 transgenic rice ]
Author: Xia Z Gao L Luo Y Deng X Li S Zhai W
Journal: Sheng Wu Gong Cheng Xue Bao Year: 2009 Type: In-Process
Literature: oryza Field: abstract Doc ID: pub19637639 Accession (PMID): 19637639
Abstract: Polymerase chain reaction ( PCR ) is a simple , quick and highly sensitive method . However the accuracy of the conventional PCR assay was often affected by false positives and false negatives . In this study , a protocol competitive PCR was used to reduce the false results in screening for selectable marker-free ( SMF ) Xa2l transgenic rice plants . The competitive template of Xa21 was the endogenous Xa2l homologous sequence located on chromosome 11 . The competitive template of the selectable marker gene , hygromycin phosphotransferase ( hpt ) , was an additive DNA extracted from hpt transgenic Nipponbare ( Oryza sativa L ) . Through competitive PCR analysis of transgenic T1 plants produced by double right border binary vector , false positive or false negative samples were effectively diminished , and genuine SMF Xa21 transgenic plants were obviously obtained . Comparing with the conventional non-competitive PCR , competitive PCR increased the accuracy for selecting SMF Xa21 transgenic plants . The results of bacterial blight ( BB ) resistance tests and hygromycin B resistance assay of SMF Xa21 transgenic plants testified the reliability of this method .
Score: 4.00
Title: A type I-secreted , sulfated peptide triggers XA21-mediated innate immunity .
Author: Lee SW Han SW Sririyanum M Park CJ Seo YS Ronald PC
Journal: Science Year: 2009 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub19892983 Accession (PMID): 19892983
Abstract: The rice Xa21 gene confers immunity to most strains of the bacterium Xanthomonas oryzae pv . oryzae ( Xoo ) . Liquid chromatography-tandem mass spectrometry analysis of biologically active fractions from Xoo supernatants led to the identification of a 194-amino acid protein designated Ax21 ( activator of XA21-mediated immunity ) . A sulfated , 17-amino acid synthetic peptide ( axY ( S ) 22 ) derived from the N-terminal region of Ax21 is sufficient for activity , whereas peptides lacking tyrosine sulfation are biologically inactive . Using coimmunoprecipitation , we found that XA21 is required for axY ( S ) 22 binding and recognition . axY ( S ) 22 is 100% conserved in all analyzed Xanthomonas species , confirming that Ax21 is a pathogen-associated molecular pattern and that XA21 is a pattern recognition receptor .
Score: 4.00
Title: Metabolomic and transcriptomic analysis of the rice response to the bacterial blight pathogen Xanthomonas oryzae pv . oryzae .
Author: Sana TR Fischer S Wohlgemuth G Katrekar A Jung KH Ronald PC Fiehn O
Journal: Metabolomics Year: 2010 Type: Publisher
Literature: oryza Field: abstract Doc ID: pub20676379 Accession (PMID): 20676379
Abstract: Bacterial leaf blight ( BLB ) , caused by Xanthomonas oryzae pv . oryzae ( Xoo ) , gives rise to devastating crop losses in rice . Disease resistant rice cultivars are the most economical way to combat the disease . The TP309 cultivar is susceptible to infection by Xoo strain PXO99 . A transgenic variety , TP309_Xa21 , expresses the pattern recognition receptor Xa21 , and is resistant . PXO99 big up tri , openraxST , a strain lacking the raxST gene , is able to overcome Xa21-mediated immunity . We used a single extraction solvent to demonstrate comprehensive metabolomics and transcriptomics profiling under sample limited conditions , and analyze the molecular responses of two rice lines challenged with either PXO99 or PXO99 big up tri , openraxST . LC-TOF raw data file filtering resulted in better within group reproducibility of replicate samples for statistical analyses . Accurate mass match compound identification with molecular formula generation ( MFG ) ranking of 355 masses was achieved with the METLIN database . GC-TOF analysis yielded an additional 441 compounds after BinBase database processing , of which 154 were structurally identified by retention index/MS library matching . Multivariate statistics revealed that the susceptible and resistant genotypes possess distinct profiles . Although few mRNA and metabolite differences were detected in PXO99 challenged TP309 compared to mock , many differential changes occurred in the Xa21-mediated response to PXO99 and PXO99 big up tri , openraxST . Acetophenone , xanthophylls , fatty acids , alkaloids , glutathione , carbohydrate and lipid biosynthetic pathways were affected . Significant transcriptional induction of several pathogenesis related genes in Xa21 challenged strains , as well as differential changes to GAD , PAL , ICL1 and Glutathione-S-transferase transcripts indicated limited correlation with metabolite changes under single time point global profiling conditions . ELECTRONIC SUPPLEMENTARY MATERIAL : The online version of this article ( doi : 10 . 1007/s11306-010-0218-7 ) contains supplementary material , which is available to authorized users .
Score: 4.00
Title: [ A PCR marker-based selection for resistance to bacterial blight in rice ]
Author: Lu C Li X Zhu L Zhang Q Yang W Zhao B Wang C
Journal: Yi Chuan Xue Bao Year: Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub8695180 Accession (PMID): 8695180
Abstract: Molecular marker-based selection in plant breeding requires not only suitable molecular markers closely linked to the known genes , but a simple , economic and reliable analyzing technique . We report here a useful PCR marker for genetic diagnostics in breeding for resistance to rice bacterial blight . Xa21 is a newly found gene of rice which confers resistance to bacterial blight caused by Xanthomonas oryzae pv . oryzae . We produced two F2 populations between one resistant line IRBB21 containing Xa21 and two susceptible varieties , respectively . One PCR marker , PB78 , detected polymorphism between the susceptible varieties and the resistant line . Cosegregation between Xa21 and PB78 was studied in the two F2 populations . The results showed that Xa21 was closely linked to the molecular marker , the crossing over value was 2 . 48% . Marker-based selection revealed that 100% of the plants with homozygous resistant genotype of PB78 showed resistance to bacterial blight . The available approaches detecting molecular markers in plant breeding are also discussed .
Score: 3.00
Title: [ Introduction of wide spectrum rice bacterial blight resistance gene Xa21 into two-line genic male sterile rice variety Peiai 64S ]
Author: Zhao B Wang WM Zheng XW Wang CL Ma BJ Xue QZ Zhu LH Zhai WX .
Journal: Sheng Wu Gong Cheng Xue Bao Year: 2000 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub10976312 Accession (PMID): 10976312
Abstract: Agrobacterium-mediated transformation of two-line genic male sterile Indica rice variety Peiai 64S was conducted using a cloned gene , Xa21 , as the foreign gene and mature embryo calli as the recipients . A total of 46 transgenic plants had been obtained . The PCR analysis and Southern blotting showed the integration of Xa21 gene into the genome the transgenic plants . Results of inoculation with philippine race 6 of Xanthomonas oryzae pv . oryzae indicated that most of transgenic plants obtained high resistance to rice bacterial blight disease ( Xoo ) . Analyses of T1 plants of the tested transgenic lines showed that integrated Xa21 gene could be steadily inherited and segregated in a 3 : 1 ratio .
Score: 3.00
Title: Are the dominant and recessive plant disease resistance genes similar? A case study of rice R genes and Xanthomonas oryzae pv . oryzae races .
Author: Li ZK Sanchez A Angeles E Singh S Domingo J Huang N Khush GS .
Journal: Genetics Year: 2001 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11606550 Accession (PMID): 11606550
Abstract: The resistance of rice to its bacterial blight pathogen Xanthomonas oryzae pv . oryzae ( Xoo ) has both qualitative and quantitative components that were investigated using three near-isogenic line sets for four resistance ( R ) genes ( Xa4 , xa5 , xa13 , and Xa21 ) and 12 Xoo races . Our results indicate that these two resistance components of rice plants were associated with the properties of the R genes . The qualitative component of the R genes was reflected by their large effects against corresponding avirulent Xoo races . The quantitative component of the R genes was their residual effects against corresponding virulent races and their epistatic effects , which together could lead to high-level resistance in a race-specific manner . Our results revealed important differences between the different types of R genes . Two R genes , Xa4 and Xa21 , showed complete dominance against the avirulent Xoo races and had large residual effects against virulent ones . They acted independently and cumulatively , suggesting they are involved in different pathways of the rice defensive system . The third R gene , xa5 , showed partial dominance or additivity to the avirulent Xoo races and had relatively small but significant residual effects against the virulent races . In contrast , xa13 was completely recessive , had no residual effects against the virulent races , and showed more pronounced race specificity . There was a strong interaction leading to increased resistance between xa13 and xa5 and between either of them and Xa4 or Xa21 , suggesting their regulatory roles in the rice defensive pathway ( s ) . Our results indicated that high-level and durable resistance to Xoo should be more efficiently achieved by pyramiding different types of R genes .
Score: 3.00
Title: [ A genetically modified japonica restorer line , C418-Xa21 , and its hybrid rice with bacterial blight resistance ]
Author: Li XB Yi CD Zhai WX Yang ZY Zhu LH .
Journal: Sheng Wu Gong Cheng Xue Bao Year: 2001 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11702691 Accession (PMID): 11702691
Abstract: The cloned bacterial blight ( BB ) resistance gene Xa21 was transferred into C418 , a major restorer line of japonica hybrid rice in China , using an Agrobacterium-mediated system . The integrated single copy of transgene displayed a 3 : 1 segregation ratio in T1 generation in PCR and resistance analyses . The transgenic homozygous C418-Xa21 lines were selected in T2 generation through PCR and resistance analyses . The selected transgenic restorer lines were then crossed with a commonly used sterile line , TijinA , to produce Xa21 transgenic hybrid rice . Molecular analysis revealed that the produced hybrid rice , named as Tiyou418-Xa21 , inherited the transgene . Both C418-Xa21 and Tiyou418-Xa21 plants displayed high resistance with a broad spectrum to Xoo races and maintained their normal elite agronomic characters . We also observed that the resistance level of Tiyou418-Xa21 was obviously higher than that of C418-Xa21 which may be attributed to their differences in genetic background . The propagation of this BB resistant hybrid variety with the transgene Xa21 with extend hybrid rice production in north China .
Score: 3.00
Title: The Xanthomonas oryzae pv . lozengeoryzae raxP and raxQ genes encode an ATP sulphurylase and adenosine-5-phosphosulphate kinase that are required for AvrXa21 avirulence activity .
Author: Shen Y Sharma P da Silva FG Ronald P
Journal: Mol . Microbiol . Year: 2002 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11967067 Accession (PMID): 11967067
Abstract: Xanthomonas oryzae pv . oryzae ( Xoo ) Philippine race 6 ( PR6 ) is unable to cause bacterial blight disease on rice lines containing the rice resistance gene Xa21 but is virulent on non-Xa21 rice lines , indicating that PR6 carries avirulence ( avrXa21 ) determinants required for recognition by XA21 . Here we show that two Xoo genes , raxP and raxQ , are required for AvrXa21 activity . raxP and raxQ , which reside in a genomic cluster of sulphur assimilation genes , encode an ATP sulphurylase and APS ( adenosine-5-phosphosulphate ) kinase . These enzymes function together to produce activated forms of sulphate , APS and PAPS ( 3-phosphoadenosine-5-phosphosulphate ) . Xoo PR6 strains carrying disruptions in either gene , PR6DeltaraxP or PR6DeltaraxQ , are unable to produce APS and PAPS and are virulent on Xa21-containing rice lines . RaxP and RaxQ are similar to the bacterial symbiont Sinorhizobium meliloti host specificity proteins , NodP and NodQ and the Escherichia coli cysteine synthesis proteins CysD , CysN and CysC . The APS and PAPS produced by RaxP and RaxQ are used for both cysteine synthesis and sulphation of other molecules . Mutation in Xoo xcysI , a homologue of Escherichia coli cysI that is required for cysteine synthesis , blocked APS or PAPS-dependent cysteine synthesis but did not affect AvrXa21 activity , suggesting that AvrXa21 activity is related to sulphation rather than cysteine synthesis . Taken together , these results demonstrate that APS and PAPS production plays a critical role in determining avirulence of a phytopathogen and reveal a commonality between symbiotic and phytopathogenic bacteria .
Score: 3.00
Title: Bacterial genes involved in type I secretion and sulfation are required to elicit the rice Xa21-mediated innate immune response .
Author: da Silva FG Shen Y Dardick C Burdman S Yadav RC de Leon AL Ronald PC .
Journal: Mol . Plant Microbe Interact . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15195942 Accession (PMID): 15195942
Abstract: Innate immunity to microorganisms relies on the specific sensing of pathogen-associated molecules by host recognition receptors . Whereas studies in animals have largely focused on the recognition of extracellular pathogen-associated molecules by the TLR ( toll-like receptor ) superfamily , few studies have been carried out in plants , and it is not understood how these molecules are secreted or modified . The rice Xa21 gene encodes a receptor-like kinase that provides immunity against strains of the bacterial pathogen Xanthomonas oryzae pv . oryzae carrying AvrXa21 activity . We identified four X oryzae pv . oryzae genes that are required for AvrXa21 activity . raxA , raxB , and raxC encode proteins with similarity to a membrane fusion protein , an ATP-binding cassette transporter , and an outer membrane protein , respectively , of bacterial type I secretion systems . The fourth gene , raxST , encodes a sulfotransferase-like protein . Sequence analysis of three naturally occurring X oryzae pv . oryzae strains no longer recognized by Xa21 revealed alterations in the raxST and raxA genes . The raxC gene complemented an Escherichia coli tolC mutant for secretion of a double glycine-leader peptide confirming the function of raxC in type I secretion . These results indicate that bacterial type I secretion is necessary for Xa21-mediated recognition and immunity and further suggest that type I secretion and modification of pathogen-associated molecules play an important role in triggering the innate immune response in rice .
Score: 3.00
Title: RaxH/RaxR : a two-component regulatory system in Xanthomonas oryzae pv . oryzae required for AvrXa21 activity .
Author: Burdman S Shen Y Lee SW Xue Q Ronald P
Journal: Mol . Plant Microbe Interact . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15195943 Accession (PMID): 15195943
Abstract: Xanthomonas oryzae pv . oryzae is the causal agent of bacterial leaf blight , one of the most serious diseases in rice . X oryzae pv . oryzae Philippine race 6 ( PR6 ) strains are unable to establish infection in rice lines expressing the resistance gene Xa21 . Although the pathogen-associated molecule that triggers the Xa21-mediated defense response ( AvrXa21 ) is unknown , six rax ( required for AvrXa21 activity ) genes encoding proteins involved in sulfur metabolism and Type I secretion were recently identified . Here , we report on the identification of two additional rax genes , raxR and raxH , which encode a response regulator and a histidine protein kinase of two-component regulatory systems , respectively . Null mutants of PR6 strain PXO99 that are impaired in either raxR , raxH , or both cause lesions significantly longer and grow to significantly higher levels than does the wild-type strain in Xa21-rice leaves . Both raxR and raxH mutants are complemented to wild-type levels of AvrXa21 activity by introduction of expression vectors carrying raxR and raxH , respectively . These null mutants do not affect AvrXa7 and AvrXa10 activities , as observed in inoculation experiments with Xa7 and Xa10-rice lines . Western blot and raxR/gfp promoter-reporter analyses confirmed RaxR expression in X oryzae pv . oryzae . The results of promoter-reporter studies also suggest that the previously identified raxSTAB operon is a target for RaxH/RaxR regulation . Characterization of the RaxH/RaxR system provides new opportunities for understanding the specificity of the X oryzae pv . oryzae-Xa21 interaction and may contribute to the identification of AvrXa21 .
Score: 3.00
Title: [ Analysis of the transgenic rice plants derived from transformed anther calli ]
Author: Jiang S Chen CY Cheng ZK Cai R Zhai WX Zhu LH .
Journal: Yi Chuan Xue Bao Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15633644 Accession (PMID): 15633644
Abstract: Rice calli derived from anther culture were used as recipient to transfer a rice blight resistance gene , Xa21 , into a japonica rice variety , Taipei 309 , via Agrobacterium-mediated transformation . Seven green transgenic plants , including one mixoploid , two haploid , and four diploid plants , were regenerated . PCR , Southern blot , FISH and blight resistance analysis all indicated that Xa21 gene has been integrated into the T0 plant genomes . T1 generations of the four diploid T0 plants were further investigated for resistance segregation . Chi2 test showed that two T1 populations segregated with a ratio of 3 : 1 , indicating that a single copy of Xa21 gene was integrated into the genome , whereas the segregation ratios of the other two T1 populations were non-Mendelian . Therefore , the four diploid transgenic plants should be heterozygous diploids .
Score: 3.00
Title: Rice NRR , a negative regulator of disease resistance , interacts with Arabidopsis NPR1 and rice NH1 .
Author: Chern M Canlas PE Fitzgerald HA Ronald PC .
Journal: Plant J Year: 2005 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub16115061 Accession (PMID): 16115061
Abstract: Arabidopsis NPR1/NIM1 is a key regulator of systemic acquired resistance ( SAR ) , which confers lasting broad-spectrum resistance . Over-expression of Arabidopsis NPR1 or the NPR1 homolog 1 ( NH1 ) in rice results in enhanced resistance to the pathogen Xanthomonasoryzae pv . oryzae ( Xoo ) , suggesting the presence of a related defense pathway in rice . We investigated this pathway in rice by identifying proteins that interact with NH1 . Here we report the isolation and characterization of a rice cDNA encoding a novel protein , named NRR ( for negative regulator of resistance ) . NRR interacts with NPR1 in the NPR1-interacting domain ( NI25 ) consisting of 25 amino acids . NRR also interacts with NH1 ; however , NI25 was not sufficient for a strong interaction , indicating a difference between the rice and the Arabidopsis proteins . Silencing of NRR in rice had little effect on resistance to Xoo . When constitutively over-expressed in rice , NRR affected basal resistance , age-related resistance and Xa21-mediated resistance , causing enhanced susceptibility to Xoo . This phenotype was correlated with elevated NRR mRNA and protein levels and increased Xoo growth . Over-expression of NRR suppressed the induction of defense-related genes . NRR : GFP ( green fluorescent protein ) protein was localized to the nucleus , indicating that NRR may act directly to suppress the activation of defense genes . The fact that NRR compromises Xa21-mediated resistance indicates cross-talk or overlap between NH1 and Xa21-mediated pathways .
Score: 3.00
Title: Perception of the chitin oligosaccharides contributes to disease resistance to blast fungus Magnaporthe oryzae in rice .
Author: Kishimoto K Kouzai Y Kaku H Shibuya N Minami E Nishizawa Y
Journal: Plant J Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub21070413 Accession (PMID): 21070413
Abstract: Chitin is a component of fungal cell walls , and its fragments act as elicitors in many plants . The plasma membrane glycoprotein CEBiP , which possesses LysM domains , is a receptor for the chitin elicitor ( CE ) in rice . Here , we report that the perception of CE by CEBiP contributes to disease resistance against the rice blast fungus , Magnaporthe oryzae , and that enhanced responses to CE by engineering CEBiP increase disease tolerance . Knockdown of CEBiP expression allowed increased spread of the infection hyphae . To enhance defense responses to CE , we constructed chimeric genes composed of CEBiP and Xa21 , which mediate resistance to rice bacterial leaf blight . The expression of either CRXa1 or CRXa3 , each of which contains the whole extracellular portion of CEBiP , the whole intracellular domain of XA21 , and the transmembrane domain from either CEBiP or XA21 , induced cell death accompanied by an increased production of reactive oxygen and nitrogen species after treatment with CE . Rice plants expressing the chimeric receptor exhibited necrotic lesions in response to CE and became more resistant to M oryzae . Deletion of the first LysM domain in CRXA1 abolished these cellular responses . These results suggest that CEs are produced and recognized through the LysM domain of CEBiP during the interaction between rice and M oryzae and imply that engineering pattern recognition receptors represents a new strategy for crop protection against fungal diseases .
Score: 3.00
Title: Enhancement of MAMP signaling by chimeric receptors improves disease resistance in plants .
Author: Kishimoto K Kouzai Y Kaku H Shibuya N Minami E Nishizawa Y
Journal: Plant Signal Behav Year: 2011 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub21364321 Accession (PMID): 21364321
Abstract: Plants activate defense responses through the recognition of microbe-associated molecular patterns ( MAMPs ) . Recently , several pattern-recognition receptors ( PRRs ) have been identified in plants , paving the way for manipulating MAMP signaling . CEBiP is a receptor for the chitin elicitor ( CE ) identified in the rice plasma membrane and XA21 is a member of the receptor-like protein kinase ( RLK ) family that confers disease resistance to rice bacterial leaf blight expressing the sulfated protein Ax21 . To improve resistance to rice blast , the most serious fungal disease of rice , we aimed to create a defense system that combines high affinity of CEBiP for CE and the ability of XA21 to confer disease resistance . Cultured rice cells expressing the chimeric receptor CRXA , which consists of CEBiP and the intracellular region of XA21 , induced cell death accompanied by an increased production of reactive oxygen and nitrogen species after exposure to CE . Rice plants expressing the chimeric receptor exhibited more resistance to rice blast Engineering PRRs may be a new strategy in molecular breeding for achieving disease resistance .
Score: 3.00
Title: Identification and expression analysis of components involved in rice Xa21-mediated disease resistance signalling .
Author: Bai H Lan JP Gan Q Wang XY Hou MM Cao YH Li LY Liu LJ Hao YJ Yin CC Wu L Zhu LH Liu GZ
Journal: Plant Biol ( Stuttg ) Year: 2012 Type: Publisher
Literature: oryza Field: abstract Doc ID: pub22672582 Accession (PMID): 22672582
Abstract: Rice Xa21 gene encodes a receptor-like kinase that confers broad-spectrum resistance against Xanthomonas oryzae pv . oryzae ( Xoo ) . Recently , a number of genes involved in the Xa21-mediated disease resistance pathway have been identified . Based on our previous data and the literature , we chose 16 candidate proteins and made corresponding antibodies . Using Western blotting , we systematically investigated the expression profile of the proteins in Xa21-mediated disease resistance response . We found nine proteins with altered expression . We further compared their expression in resistance , susceptible and mock responses , and found that GST expression was up-regulated during the resistance process , indicating GST is a positive regulator in resistance responses . ATPsB expression was down-regulated during both the resistance and susceptible response processes , although it was higher in the resistance response than that in the susceptible response . The total amount of MYB , GAPDH , CatB , Trx and NB-ARC proteins was lower in the resistance than in the susceptible response , but their abundance per unit bacteria in the resistance response was still higher than in the susceptible response , suggesting that these proteins might be positive regulators in the resistance response . In addition , expression of another ERF was induced by inoculation with bacterial blight pathogen , and expression of Zf-LSD1 was activated by wounding stress alone . Interestingly , most proteins showed similar altered expression patterns in the resistance and susceptible responses , but differed to some extents , implying that both responses might share common molecular mechanisms . This study revealed evidence of resistance-related protein expression , providing a foundation for better understanding of their functions .
Score: 3.00
Title: A receptor kinase-like protein encoded by the rice disease resistance gene , Xa21 .
Author: Song WY Wang GL Chen LL Kim HS Pi LY Holsten T Gardner J Wang B Zhai WX Zhu LH Fauquet C Ronald P
Journal: Science Year: 1995 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub8525370 Accession (PMID): 8525370
Abstract: The rice Xa21 gene , which confers resistance to Xanthomonas oryzae pv . oryzae race 6 , was isolated by positional cloning . Fifty transgenic rice plants carrying the cloned Xa21 gene display high levels of resistance to the pathogen . The sequence of the predicted protein , which carries both a leucine-rich repeat motif and a serine-threonine kinase-like domain , suggests a role in cell surface recognition of a pathogen ligand and subsequent activation of an intracellular defense response . Characterization of Xa21 should facilitate understanding of plant disease resistance and lead to engineered resistance in rice .
Score: 3.00
Title: The molecular basis of disease resistance in rice .
Author: Ronald PC .
Journal: Plant Mol . Biol . Year: 1997 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub9291971 Accession (PMID): 9291971
Abstract: The rice gene Xa21 conferring resistance to Xanthomonas oryzae pv . oryzae ( Xoo ) , was isolated using a map-based cloning strategy . Compared with previously cloned genes , the structure of Xa21 represents a novel class of plant disease R genes encoding a putative receptor kinase ( RK ) . This article proposes a model for the mode of action of Xa21 and summarizes our current knowledge of the modular basis of resistance in rice to bacterial leaf blight and blast
Score: 2.00
Title: [ Amplification and analysis of T-DNA flanking sequences in transgenic rice ]
Author: Fang J Zhai WX Wang WM Li SW Zhu LH .
Journal: Yi Chuan Xue Bao Year: Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11329876 Accession (PMID): 11329876
Abstract: Rice transformation mediated by Agrobacterium tumefaciens has technically matured to some extent , but the mechanics of T-DNA integration in transgenic rice remains largely unknown . Using thermal asymmetric interlaced PCR ( TAIL-PCR ) , we analyzed the flanking sequences of T-DNAs in transgenic rice plants , in which the resistance gene for rice bacterial blight disease , Xa21 , had been integrated stably . Sequence analysis of 24 fragments amplified by TAIL-PCR showed that of them 14 were rice genomic DNA , 9 contained vector backbone sequences , and one was a fragment of the exogenous gene Xa21 . The characteristics of the 14 rice genomic DNA sequences at T-DNA integrated sites are significantly different from those of the reported rice genomic sequences into which exogenous genes were integrated through direct DNA transformation methods . T-DNA border sequences integrated in rice genome have similar features as those integrated in dicotyledonous genomes . In the backbone containing flanking sequences ( 37 . 5% , 9/24 ) vector backbones appeared in different types .
Score: 2.00
Title: Marker assisted selection of bacterial blight resistance genes in rice .
Author: Davierwala AP Reddy AP Lagu MD Ranjekar PK Gupta VS .
Journal: Biochem . Genet . Year: 2001 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11590832 Accession (PMID): 11590832
Abstract: Bacterial leaf blight caused by Xanthomonas oryzae pv . oryzae is one of the most important diseases affecting rice production in Asia . We were interested in surveying rice genotypes that are popularly used in the Indian breeding program for conferring resistance to bacterial blight , using 11 STMS and 6 STS markers . The basis of selection of these DNA markers was their close linkage to xa5 , xa13 , and Xa21 genes and their positions on the rice genetic map relative to bacterial blight resistance genes . Eight lines were found to contain the xa5 gene while two lines contained Xa21 gene and none of the lines contained the xa13 gene with the exception of its near-isogenic line . Using the polymorphic markers obtained in the initial survey , marker-assisted selection was performed in the F3 population of a cross between IR-64 and IET-14444 to detect lines containing multiple resistance genes . Of the 59 progeny lines analyzed , eight lines contained both the resistance genes , xa5 and Xa4 .
Score: 2.00
Title: [ Study on the teratogenicity effects of genetically modified rice with Xa21 on rats ]
Author: Li Y Piao J Zhuo Q Chen X Mao D Yang L Yang X
Journal: Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15727184 Accession (PMID): 15727184
Abstract: OBJECTIVE : To observe the effects of genetically modified rice with Xa21 on the development of rat embryos . METHODS : According to sex , weanling rats were divided into four groups : transgenic rice group , non-transgenic rice group , AIN93G negative control group and MATDA positive control group . The rats were fed with corresponding food for 90 days and mated . The development of maternal rats and embryos were observed . RESULTS : The body weight gain of pregnant rats and the body weight , body length and tail length of fetal rats in transgenic rice group were significant increased than those in positive control group . The number of death embryos and adsorption embryos , the malformation rate ( appearance , viscera , skeleton ) in transgenic rice group were lower than those in positive control group . There were no significant difference of all indicators among transgenic rice group , non-transgenic rice group and AIN93G negative control group . CONCLUSION : Compared with the non-transgenic rice , transgenic rice modified with Xa21 gene showed no significant differences in rat pregnant rate and embryo development .
Score: 2.00
Title: [ Effects of transgenes insertion on pollen vigor and hybrid seed set of rice ]
Author: Wei X Yuan X Yu H Wang Y Tang S Liao X
Journal: Year: 2005 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15852969 Accession (PMID): 15852969
Abstract: In this paper , the effects of transgenes insertion on the outcross potentiality of rice varieties were assessed by pollen vigor and hybrid seed set . The in vitro pollen germination rates of five transgenic rice lines transformed respectively with bar , crylAb , BADH and Xa21 gene were investigated , and compared with their relative receptor rice varieties . The results showed that there existed a significant difference in in vitro pollen germination rates between receptor rice varieties , but no significant difference was found between transgenic rice varieties and their relative receptors . The in vitro pollen germination rate for transgenic rice varieties varied from 0 . 416 to 0 . 584 , similar to that of their relative receptors ( 0 . 400-0 . 574 ) . Investigation on the hybrid seed set of 26 hand-crosses showed that the inserted bar or crylAb gene had a significant effect on the hybrid seed set of receptors , while the effect of Xa21 gene was smaller . The hybrid seed set rate of non-transgenic rice in crosses with transgenic rice ( pollen donor ) was from 0 . 056 to 0 . 413 , not different from that in crosses with their relative receptors ( 0 . 052-0 . 417 ) . Its suggested that transgenes insertion had little effect on the outcross potentiality of rice varieties .
Score: 2.00
Title: From the Academy : Colloquium review . Unique characteristics of Xanthomonas oryzae pv . oryzae AvrXa21 and implications for plant innate immunity .
Author: Lee SW Han SW Bartley LE Ronald PC .
Journal: Proc . Natl . Acad . Sci . USA Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub17082309 Accession (PMID): 17082309
Abstract: This article provides a brief overview of some of the major concepts and molecular features of plant and animal innate immune systems . The rice pathogen recognition receptor , XA21 , confers resistance to Xanthomonas oryzae pv . oryzae strains producing the AvrXa21 elicitor . Xa21 codes for a receptor-like kinase consisting of an extracellular leucine-rich repeat domain , a transmembrane domain , and a cytoplasmic kinase domain . We show that AvrXa21 activity requires the presence of rax ( required for AvrXa21 ) A , raxB , and raxC genes that encode components of a type one secretion system . In contrast , an hrpC ( - ) strain deficient in type three secretion maintains AvrXa21 activity . Xanthomonas campestris pv . campestris can express AvrXa21 activity if raxST , encoding a putative sulfotransferase , and raxA are provided in trans . Expression of rax genes depends on population density and other functioning rax genes . This and other data suggest that the AvrXa21 pathogen-associated molecule is involved in quorum sensing . Together these data suggest that AvrXa21 represents a previously uncharacterized class of Gram-negative bacterial signaling molecules . These results from our studies of the XA21/AvrXa21 interaction call for some modifications in the way we think about innate immunity strategies .
Score: 2.00
Title: Adapting rice anther culture to gene transformation and RNA interference .
Author: Chen C Xiao H Zhang W Wang A Xia Z Li X Zhai W Cheng Z Zhu L
Journal: Sci . China , C , Life Sci . Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub17172048 Accession (PMID): 17172048
Abstract: Anther culture offers a rapid method of generating homozygous lines for breeding program and genetic analysis . To produce homozygous transgenic lines of rice ( Oryza sativa L ) in one step , we developed an efficient protocol of anther-callus-based transformation mediated by Agrobacterium after optimizing several factors influencing efficient transformation , including callus induction and Agrobacterium density for co-cultivation . Using this protocol , we obtained 145 independent green transformants from five cultivars of japonica rice by transformation with a binary vector pCXK1301 bearing the rice gene , Xa21 for resistance to bacterial blight , of which 140 were further confirmed by PCR and Southern hybridization analysis , including haploids ( 32 . 1% ) , diploids ( 62 . 1% ) and mixoploids ( 7 . 5% ) . Fifteen diploids were found to be doubled haploids , which accounted for 10 . 7% of the total positive lines . Finally , by including 28 from colchicine induced or spontaneous diploidization of haploids later after transformation , a total of 43 doubled haploids ( 30 . 7% ) of Xa21 transgenic lines were obtained . We also generated two RNAi transgenic haploids of the rice OsMADS2 gene , a putative redundant gene of OsMADS4 based on their sequence similarity , to investigate its possible roles in rice flower development by this method . Flowers from the two OsMADS2 RNAi transgenic haploids displayed obvious homeotic alternations , in which lodicules were transformed into palea/lemma-like it issues , whereas identities of other floral organs were maintained . The phenotypic alternations were proved to result from specific transcriptional suppression of OsMADS2 gene by the introduced RNAi transgene . The results confirmed that OsMADS2 is involved in lodicule development of rice flower and functionally redundant with OsMADS4 gene . Our results demonstrated that rice anther culture could be adapted to gene transformation and RNAi analysis in rice .
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