OsNCED3 and OsPYL1 promote the closure of rice florets by regulating sugar transporters through endogenous abscisic acid

Abstract

As the world's largest food crop, rice often encounters flowering asynchronization problems during hybrid rice seed production. In addition, the slow closure of female florets leads to seed mildew and affects the quality. Plant hormone abscisic acid (ABA) plays a crucial role in plant responses to abiotic stresses. Previous studies showed that exogenous ABA promotes floret closure. However, the molecular mechanisms and effects of endogenous ABA on floret closure remain unknown. In this study, the effect of endogenous ABA on floret closure and the molecular mechanism of ABA promoting floret closure through sugar transporters were investigated by changing the expression level of OsNCED3 and OsPYL1 in rice. The results show that OE-OsNCED3 increases the endogenous ABA level of florets. Florets close 5.91 min earlier and CR-OsNCED3 delays the closure of florets by 5.08 min compared with the wild type. In addition, OsPYL1 regulates the endogenous ABA content and changes the sensitivity to ABA such that the floret closure time for OE and CR is 9.84 min earlier and 12.78 min later, respectively, resulting in an increase in the split husk rate to 15.4%. The gene expression levels of some sugar transporters (STs) changed. OsPYL1 and OsSWEET4 proteins could interact on the cell membrane. These results indicate that ABA promotes the closure of rice florets and an enhanced sensitivity to ABA promotes this effect more. The molecular mechanism is mainly related to downstream sugar transporters that respond to the ABA signalling pathway, especially OsSWEET4.