BLS1,BSG1,OsG1L6,TH1,AFD1

| Categories genes  | Tags inflorescence  architecture  lemma  cell division  grain size  palea  grain  spikelet  cell cycle  stem  starch  floral  panicle  sterile  seed  grain yield  yield  floral organ  development  nucleus 
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  • Key message
    • BLS1 is expressed strongly in young inflorescence, specifically the young lemmas and paleas of spikelets
    • In bls1 mutant, floral-organ identity and floral-organ patterning are normal, and the defects occur at the stage of the lemma and palea expansion, whereas the other aspects of floral architecture and form are not affected
    • Here, we isolated a rice mutant, beak-shaped grain1 (bsg1), which produced beak-shaped grains of decreased width, thickness and weight with a loosely interlocked lemma and palea that were unable to close tightly
    • Consistent with the lemma and palea shapes, the outer parenchyma cell layers of these bsg1 tissues developed fewer cells with decreased size
    • Our results suggest that BSG1 determines grain shape and size probably by modifying cell division and expansion in the grain hull
    • The BSG1 mutation affected the expression of genes potentially involved in the cell cycle and GW2, an important regulator of grain size in rice
    • Starch granules were also irregularly packaged in the bsg1 grains
    • In this study, we characterized a rice mutant, beak like spikelet1 (bls1), which specifically affects development of the lemma and palea
    • Our study suggested that BLS1 is required for lateral development of the lemma and palea and does not function at stages of floral-organ initiation and patterning
    • Quantitative PCR and GUS fusion reporter assays showed that BSG1 was expressed mainly in the young panicle and elongating stem
    • Expression of the AP1-like and SEP-like floral homeotic genes were not changed in the bls1 mutant
    • Detailed morphological analysis indicated that the th1 mutation caused a reduction in the size of tubercles, which are convex structures on the surface of the lemma and palea
    • Thus, the TH1 gene seems to be involved in fine-tuning the morphogenesis of the lemma and palea
    • By contrast, the number of tubercle rows and their spatial distribution on the lemma were not affected in the th1 mutant
    • In situ hybridization analysis revealed that TH1 was highly expressed in the primordia of the lemma and palea, but only weakly expressed in the primordia of the sterile lemma and rudimentary glume
    • The result showed that the th1 mutation strongly affected the morphology of the extra lemma of eg1, but had no significant effect on the transformed lemma of g1
    • We then examined the effect of th1 mutation on the lemma-like structure formed in the long sterile lemma/glume1 (g1) and extra glume1 (eg1) mutants
    • The afd1 mutant showed variable defects including the dwarfism, long panicle, low seed setting and reduced grain yield
    • Meantime, our results suggested that AFD1 regulated the expression of cell division and expansion related genes
    • In addition, abnormal floral organs were also observed in the afd1 mutant including slender and thick hulls, and hull-like lodicules
    • These results indicate that TH1 functions as a transcription repressor and regulates cell expansion during the lateral development of spikelet
    • TH1 has been shown to regulate the lateral development of spikelet, but its mode of action remains unclear
    • The TH1 protein was shown to localize in the nucleus and possess transcriptional repression activity
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