| Categories genes  | Tags senescence  seedling  oxidative  leaf  cytokinin  chloroplast  cell death  grain  grain yield  yield  breeding 
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    • SGR, like the gene for pheophorbide a oxygenase (PaO), was constitutively expressed, but was upregulated by dark-induced senescence in rice leaves
    • Senescence-induced expression of SGR and PaO was enhanced by ABA, but inhibited by cytokinin
    • This indicates that upregulation of SGR increases Chl breakdown during senescence in rice
    • A small quantity of chlorophyllide a accumulated in sgr leaves, but this also accumulated in wild-type rice leaves during senescence
    • In this study, we found that overexpression of SGR (Ov-SGR) resulted in the generation of singlet oxygen and other reactive oxygen species and produced a chlorophyll-dependent regional cell death phenotype on leaves of rice seedlings
    • Transcriptome analyses using Affymetrix Rice GeneChips revealed that Ov-SGR rice seedlings exhibited a number of signs of singlet oxygen response
    • Overexpression of SGR results in oxidative stress and lesion-mimic cell death in rice seedlings
    • The Stay-Green Rice (SGR) protein is encoded by the SGR gene and has been shown to affect chlorophyll (Chl) degradation during natural and dark-induced leaf senescence
    • We show that SGRL is primarily expressed in green tissues, and is significantly downregulated in rice leaves undergoing natural and dark-induced senescence
    • Overexpression of SGRL reduces the levels of Chl and Chl-binding proteins in leaves, and accelerates their degradation in dark-induced senescence leaves in rice
    • The gene, designated Stay Green Rice (SGR), was cloned by a positional cloning strategy encoding an ancient protein containing a putative chloroplast transit peptide
    • It is thought that the Stay Green Rice (SGR) gene is involved in the disaggregation of the light harvesting complex and in the subsequent breakdown of chlorophyll and apo-protein during senescence
    • Promoter variations in the Stay-Green (OsSGR) gene encoding the chlorophyll-degrading Mg++-dechelatase were found to trigger higher and earlier induction of OsSGR in indica, which accelerated senescence of indica rice cultivars
    • Japonica OsSGR alleles introgressed into indica-type cultivars in Korean rice fields lead to delayed senescence, with increased grain yield and enhanced photosynthetic competence
    • Taken together, these data establish that naturally occurring OsSGR promoter and related lifespan variations can be exploited in breeding programs to augment rice yield
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