High temperature (HT) is a main environmental restraint that affects rice yield and grain quality. In this study, SSIIIa-RNAi and its wild-type (WT) were used to investigate the effect of HT exposure on the isozyme-specific variation of several key starch biosynthesis enzymes in developing endosperms and its relation to starch properties. SSIIIa-RNAi had minimal impact on grain chalky occurrence under normal temperature growth, but it could up-grade the susceptibility of grain chalky occurrence to HT exposure, due to the relatively sensitive response of AGPase and SSI to HT exposure. Different from WT, SSIIIa-RNAi had the relatively enriched proportion of chains with DP 13-16 under HT, and HT-induced decline in the proportion of DP < 12 became much larger for SSIIIa-RNAi relative to WT. SSIIIa-RNAi significantly enhanced the expression of SSI isozyme and total SS activity, whereas SSI-RNAi deficiency had little impact on the expression of SSIIIa isozyme. In this regard, the compensatory increase in SSI isozyme as a result of SSIIIa deficiency occurred only in a one-way manner. SSIIIa-RNAi caused a striking elevation in BEIIa expression, and the effect of SSIIIa deficiency on the chain length distribution in relation to HT exposure was closely associated with the participation of BEIIa, SSI, and their interaction in amylopectin biosynthesis.

中文翻译：

---

SSIIIa-RNAi抑制高温对水稻籽粒品质和淀粉生物合成代谢的影响

高温（HT）是影响水稻产量和籽粒品质的主要环境制约因素。在这项研究中，SSIIIa-RNAi 及其野生型 (WT) 用于研究 HT 暴露对发育胚乳中几种关键淀粉生物合成酶的同工酶特异性变异的影响及其与淀粉特性的关系。SSIIIa-RNAi在常温生长条件下对谷物白垩发生的影响很小，但由于AGPase和SSI对HT暴露的反应相对敏感，它可以提高谷物白垩发生对HT暴露的敏感性。与WT不同，SSIIIa-RNAi在HT下具有DP 13-16的链的比例相对富集，并且相对于WT，SSIIIa-RNAi的HT诱导的DP < 12比例下降要大得多。SSIIIa-RNAi显着增强了SSI同工酶的表达和总SS活性，而SSI-RNAi缺乏对SSIIIa同工酶的表达影响不大。在这方面，由于 SSIIIa 缺乏导致 SSI 同工酶的补偿性增加仅以一种方式发生。SSIIIa-RNAi 导致 BEIIa 表达显着升高，SSIIIa 缺乏对与 HT 暴露相关的链长分布的影响与 BEIIa、SSI 及其在支链淀粉生物合成中的相互作用密切相关。