Abscisic acid and the key enzymes and genes in sucrose-to-starch conversion in XXXX spikelets in response to soil drying during grain filling.

@entity2133 @entity579 @entity14962
MAIN CONCLUSION: Abscisic acid mediates the effect of post-anthesis soil drying on grain filling through regulating the activities of key enzymes and expressions of genes involved in sucrose-to-starch conversion in @entity579 spikelets. This study investigated if abscisic acid (ABA) would mediate the effect of post-anthesis soil drying on grain filling through regulating the key enzymes in sucrose-to-starch conversion in @entity579 ( @entity579 .) spikelets. Two @entity579 cultivars were field-grown. Three treatments, @entity14962 ( @entity14962 ), @entity2133 ( @entity2133 ), and severe soil drying (SD), were imposed from 6  days after full heading until maturity. When compared with those under the @entity14962 , grain filling rate, grain weight, and sink activity, in terms of the activities and gene expression levels of sucrose synthase, ADP glucose pyrophosphorylase, starch synthase, and starch branching enzyme, in inferior spikelets were substantially increased under the @entity2133 , whereas they were markedly decreased in both superior and inferior spikelets under the SD. The two cultivars showed the same tendencies. Both @entity2133 and SD increased ABA content and expression levels of its biosynthesis genes in spikelets, with more increase under the SD than the @entity2133 . ABA content was significantly correlated with grain filling rate and sink activities under both @entity14962 and @entity2133 , while the correlations were not significant under the SD. Application of a low concentration ABA to @entity14962 plants imitated the results under the @entity2133 , and applying with a high concentration ABA showed the effect of the SD. The results suggest that ABA plays a vital role in grain filling through regulating sink activity and functions in a dose-dependent manner. An elevated ABA level under the @entity2133 enhances, whereas a too high level of ABA under the SD decreases, sink activity.
