OsSAUR55 Regulates Rice Plant Type Through GA Pathway
Knockout mutants ossaur55-1 and ossaur55-2 obtained by CRISPR/Cas9 technology in Francis background were used as research objects to study whether they affect the changes of agronomic traits such as plant type,leaf color,ear weight per plant and seed setting rate of rice.To explore whether OsSAUR55 regulates rice plant type by participating in GA pathway,and to provide theoretical basis for regulating rice plant type by related hor-mone pathway.The main agronomic traits of wild type(WT)and knockout mutant in adult plant stage were exam-ined,including plant height,ear length,ear weight per plant,ten grain length,ten grain width,blade length,and blade width.Chlorophyll content and net photosynthetic rate of wild type and mutant leaf were measured by chloro-phyll meter and photosynthetic rate meter.Real-time Fluorescence Quantitative PCR(qPCR)was used to determine the expression of OsSAUR55 gene in different tissues and different time points of rice seed germination.The subcel-lular localization of OsSAUR55 protein was observed by prokaryotic expression method.The contents of endogenous hormones(GA and IAA)in wild type and mutant were determined by liquid chromatography-tandem mass spectrom-etry(LC-MS/MS).The expression of genes related to GA pathway was further analyzed.In the adult plant stage,mutant ossaur55-1 and ossaur55-2 showed significant phenotypic changes,in which the mutant was significantly shorter in plant height,greener in leaf color,increased in chlorophyll content,decreased in photosynthetic efficien-cy,decreased in seed setting rate,decreased in 1000-grain weight and decreased in panicle weight per plant than the wild type.The quantitative results showed that OsSAUR55 expression was the highest in the plumule,but not in the flag leaf.Confocal results showed that OsSAUR55 may be localized in cell membrane and nucleus.The results of hormone detection showed that the content of GA4 was decreased significantly.Gene expression analysis showed that the expression levels of genes KAO,GA13 ox1,GA20 ox1 and KO1 in the GA synthesis pathway were significantly higher than those of the wild type,and the expression levels of GA2 ox5,GA2 ox8 and GA2 ox9 in the GA metabolic pathway were also significantly higher than those of the wild type.It is preliminarily speculated that the deletion of OsSAUR55 gene led to the decrease of endogenous GA4 content,which may regulate rice plant type through GA pathway,and then affect rice yield.
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