不同穗发芽抗性水稻品种间差异的生理基础OA

To reveal the physiological mechanism underlying the varietal difference in pre-harvest sprouting(PHS)resistance of rice,three rice varieties with different PHS resistance levels(the resistant type-Nanjing 9108,the sensitive type-Suken 118 and the moderate resistant type-Nanjing 505)were selected for this study.Indicators including panicle germination rate,relative water content,total soluble sugar content,sugar component contents,and α-amylase activity were measured at different stages post-anthesis.The results showed that the contents of total soluble sugars,sucrose,and trehalose in rice seeds gradually increased with post-flowering,and varietal differences in panicle germination became apparent 35 days after flowering(DAF).Artificially simulation germination tests on panicles at 35 DAF indicated that in the PHS-susceptible variety Suken 118,the expression levels of endogenous sugar signal-related gene(OsTOR,OsRaptor1,OsSnRK1A,and OsHXK5)was significantly induced early.This induction further unregulated the expression levels of abscisic acid(ABA)degradation genes(OsABA8ox1 and OsABA8ox3)and gibberellin(GA)biosynthesis gene(OsGA3ox1),followed by an increase in the expression level of the α-amylase hydrolysis gene(RAmy1A),ultimately resulting in a high germination rate.In contrast,in the PHS-resistant variety Nanjing 9108,changes in sugar content were insignificantly,and the induction of sugar signal-related genes was delayed.The expression of ABA biosynthesis gene(OsNCED1)was rapidly upregulated with the prolonged treatment,while the expression level of RAmy1A was low,exhibiting characteristics of the low germination rate.In conclusion,the differences in sensitivity to sugar levels among rice varieties is closely related to theirdifferences in PHS resistance.This study provides the new clues for analyzing varietal difference in rice PHS resistance from in the perspective of sugar signaling.