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| Title: Initiation of shoot apical meristem in rice : characterization of four SHOOTLESS genes .
| | Author: Satoh N Hong SK Nishimura A Matsuoka M Kitano H Nagato Y | | Journal: Development Citation: V : 126 ( 16 ) P : 3629-36 Year: 1999 Type: ARTICLE | | Literature: oryza Field: abstract Doc ID: pub10409508 Accession (PMID): 10409508 | | Abstract: The regulatory mechanism of shoot apical meristem ( SAM ) initiation is an important subject in developmental plant biology .
We characterized nine recessive mutations derived from four independent loci ( SHL1-SHL4 ) causing the deletion of the SAM .
Radicles were produced in these mutant embryos .
Concomitant with the loss of SAM , two embryo-specific organs , coleoptile and epiblast , were lost , but the scutellum was formed normally .
Therefore , differentiation of radicle and scutellum is regulated independently of SAM , but that of coleoptile and epiblast may depend on SAM .
Regeneration experiments using adventitious shoots from the scutellum-derived calli showed that no adventitious shoots were regenerated in any shl mutant .
However , small adventitious leaves were observed in both mutant and wild-type calli , but they soon became necrotic and showed no extensive growth .
Thus , leaf primordia can initiate in the absence of SAM , but their extensive growth requires the SAM .
An in situ hybridization experiment using a rice homeobox gene , OSH1 , as a probe revealed that shl1 and shl2 modified the expression domain of OSH1 , but normal expression of OSH1 was observed in shl3 and shl4 embryos .
Accordingly , SHL1 and SHL2 function upstream of OSH1 , and SHL3 and SHL4 downstream or independently of OSH1 .
These shl mutants are useful for elucidating the genetic program driving SAM initiation and for unraveling the interrelationships among various organs in grass embryos . | Matching Sentences:
[ Sen. 9, subscore: 1.00 ]: An in situ hybridization experiment using a rice homeobox gene , OSH1 , as a probe revealed that shl1 and shl2 modified the expression domain of OSH1 , but normal expression of OSH1 was observed in shl3 and shl4 embryos .
[ Sen. 10, subscore: 1.00 ]: Accordingly , SHL1 and SHL2 function upstream of OSH1 , and SHL3 and SHL4 downstream or independently of OSH1 .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
Score: 1.00 |
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| Title: The small interfering RNA production pathway is required for shoot meristem initiation in rice .
| | Author: Nagasaki H Itoh J Hayashi K Hibara K Satoh-Nagasawa N Nosaka M Mukouhata M Ashikari M Kitano H Matsuoka M Nagato Y Sato Y | | Journal: Proc Natl Acad Sci U S A Citation: V : 104 P : 14867-71 Year: 2007 Type: MEDLINE | | Literature: oryza Field: abstract Doc ID: pub17804793 Accession (PMID): 17804793 | | Abstract: The shoot apical meristem ( SAM ) is a group of stem cells that are responsible for plant development .
Mutations in rice SHOOTLESS2 ( SHL2 ) , SHL4/SHOOT ORGANIZATION2 ( SHO2 ) , and SHO1 cause complete deletion or abnormal formation of the SAM .
In this study we showed that defects in SAM formation in shl mutants are associated with the loss of expression of the homeodomain-leucine zipper ( HD-ZIPIII ) family genes .
Rice SHL2 , SHL4/SHO2 , and SHO1 encoded orthologues of Arabidopsis RNA-dependent RNA polymerase 6 , ARGONAUTE ( AGO ) 7 , and DICER-like 4 , respectively , whose mutations affect leaf development through the trans-acting siRNA ( ta-siRNA ) pathway .
This suggested that the ta-siRNA pathway regulates the critical step of SAM formation during rice embryogenesis .
The gain-of-function experiment by the ectopic expression of SHL4 resulted in reduced accumulation of an microRNA , miR166 , and partial adaxialization of leaves , supporting a role for the ta-siRNA pathway in the maintenance of leaf polarity as previously reported in maize .
Analysis of the spatiotemporal expression patterns of HD-ZIPIII and miR166 in wild-type and shl mutant embryos suggested that the loss of HD-ZIPIII expression in the SAM region of the developing embryo is the result of ectopic expression of miR166 .
Our analysis of shl mutants demonstrated that HD-ZIPIII expression regulated by miR166 is sensitive to the ta-siRNA pathway during SAM formation in rice embryogenesis .
| Matching Sentences:
[ Sen. 6, subscore: 1.00 ]: The gain-of-function experiment by the ectopic expression of SHL4 resulted in reduced accumulation of an microRNA , miR166 , and partial adaxialization of leaves , supporting a role for the ta-siRNA pathway in the maintenance of leaf polarity as previously reported in maize .
| | Supplemental links/files: reference in endnote online text related articles pubmed citation | |
