title: Abscisic acid and the key enzymes and genes in sucrose-to-starch conversion in rice spikelets in response to soil drying during grain filling.
abstract: 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 rice 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 rice (Oryza sativa L.) spikelets. Two rice cultivars were field-grown. Three treatments, well-watered (WW), moderate soil drying (MD), and severe soil drying (SD), were imposed from 6 days after full heading until maturity. When compared with those under the WW, 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 MD, whereas they were markedly decreased in both superior and inferior spikelets under the SD. The two cultivars showed the same tendencies. Both MD and SD increased ABA content and expression levels of its biosynthesis genes in spikelets, with more increase under the SD than the MD. ABA content was significantly correlated with grain filling rate and sink activities under both WW and MD, while the correlations were not significant under the SD. Application of a low concentration ABA to WW plants imitated the results under the MD, 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 MD enhances, whereas a too high level of ABA under the SD decreases, sink activity.
authors.affiliation: Jiangsu Key Laboratory of Crop Genetics and Physiology, Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou, 225009, China.
authors.forename: Zhiqin
authors.initials: Z
authors.lastname: Wang
authors.forename: Yunji
authors.initials: Y
authors.lastname: Xu
authors.forename: Tingting
authors.initials: T
authors.lastname: Chen
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Jianchang
authors.initials: J
authors.lastname: Yang
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000040:Abscisic Acid / Q000502:physiology*; D002241:Carbohydrates; D002734:Chlorophyll / Q000378:metabolism; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism; D012987:Soil; D013213:Starch / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D002241:Carbohydrates; D012987:Soil; D002734:Chlorophyll; D013395:Sucrose; D000040:Abscisic Acid; D013213:Starch