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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 .
Journal: J Biol Chem Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20118235
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 .
Journal: Mol Plant Year: 2010 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub20616165
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 .
Journal: Genetica Year: 2011 Type: In-Process
Literature: oryza Field: abstract Doc ID: pub22451352
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 .
Journal: J Biol . Chem . Year: 2002 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub11927577
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 .
Journal: Year: 2006 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub17172358
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 .
Journal: PLoS Biol Year: 2008 Type: MEDLINE
Literature: oryza Field: abstract Doc ID: pub18817453
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 .
Journal: Plant Cell Year: 1998 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub9596635
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 .
Journal: Mol . Gen . Genet . Year: 1992 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub1362973
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 .
Journal: Theor . Appl . Genet . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub14523518
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 .
Journal: Theor . Appl . Genet . Year: 2004 Type: ARTICLE
Literature: oryza Field: abstract Doc ID: pub15088086
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 .

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