The rice miR171b–SCL6-IIs module controls blast resistance,grain yield,and flowering

Micro RNAs(mi RNAs)act as regulators of plant development and multiple stress responses.Here we demonstrate that the rice mi R171 b-SCL6-IIs module regulates the balance between blast resistance,grain yield,and flowering.mi R171 b-overexpressing rice plants(OX171 b)displayed increased rice blast resistance accompanied with enhanced defense responses and late heading,whereas blocking mi R171 b expression in rice(MIM171)led to greater susceptibility to blast disease,associated with compromised defense responses and early heading.Either overexpressing or silencing of mi R171 b significantly affected plant height and number of filled seeds per panicle(seed-setting rate),resulting in decreased grain yield.mi R171 b targets SCL6-IIa,SCL6-IIb,and SCL6-IIc,whose expression was suppressed in OX171 b but increased in MIM171.Mutants of SCL6-IIa,SCL6-IIb,and SCL6-IIc all displayed phenotypes like that of OX171 b,including markedly increased blast disease resistance,slightly decreased grain yield,and delayed flowering.Amounts of mi R171 b increased gradually in leaves during the vegetative stage but decreased gradually in panicles during the reproductive stage,whereas SCL6-IIs displayed the reverse expression pattern.Together,these results suggest that the expression of mi R171 b was time-and space-dependent during the rice growth period and regulated the balance between rice blast disease resistance,grain yield,and flowering via SCL6-IIs,and that appropriate accumulation of mi R171 b is essential for rice development.