China National Rice Research Institute, State Key Laboratory of Rice Biology, Hangzhou, 310006, China; College of Agronomy, Jiangxi Agricultural University, Nanchang, 330045, China.
China National Rice Research Institute, State Key Laboratory of Rice Biology, Hangzhou, 310006, China.
Plant Physiol Biochem. 2018 Dec;133:1-10. doi: 10.1016/j.plaphy.2018.10.020. Epub 2018 Oct 19.
GA is important for rice seed germination, and seed embryo growth relies on sugar supplementation via starch hydrolysis in the endosperm. Low temperature reduces the seed germination rates of rice; however, the mechanism of GA metabolism and its impact on sugar utilization of germinating seeds under low temperature conditions remain poorly understood. In this study, low-temperature (15 °C) treatment delayed rice (Oryza sativa L.) seed germination, promoted GA deactivation, inhibited GA signal transduction, and increased ABA synthesis in the seed compared with normal treatment (30 °C). Under low temperature conditions, the soluble sugar content in endosperm was reduced along with depression of the specific activity levels of α-amylase (EC 3.2.1.1) and β-amylase (EC 3.2.1.2), but the soluble sugar content was increased in the embryo compared with the control treatment. Low temperature treatment promoted sugar transportation from endosperm to embryo and reduced the activity levels of enzymes involved in glycolysis and the tricarboxylic acid cycle, which participated in sugar consumption. Exogenous GA application (10 μM) prompted GA signal transduction and inhibited ABA synthesis, while enhancing starch hydrolysis and sugar consumption to boost rice seed germination under low temperature conditions. In conclusion, a deficiency of bioactive GAs in rice seeds exposed to low temperature led to a decrement in starch hydrolysis and sugar consumption, thus inhibit seed germination.
GA 对水稻种子萌发很重要，而种子胚胎的生长依赖于胚乳中淀粉水解产生的糖的补充。低温会降低水稻种子的萌发率；然而，GA 代谢在低温条件下对萌发种子糖利用的机制及其影响仍知之甚少。在这项研究中，低温（15°C）处理延迟了水稻（Oryza sativa L.）种子的萌发，促进了 GA 的失活，抑制了 GA 信号转导，并增加了种子中 ABA 的合成，与正常处理（30°C）相比。在低温条件下，胚乳中的可溶性糖含量降低，同时α-淀粉酶（EC 3.2.1.1）和β-淀粉酶（EC 3.2.1.2）的比活水平受到抑制，但与对照处理相比，胚中的可溶性糖含量增加。低温处理促进了糖从胚乳向胚的运输，并降低了参与糖消耗的糖酵解和三羧酸循环中酶的活性水平。外源 GA 的应用（10μM）促进了 GA 信号转导，抑制了 ABA 的合成，同时增强了淀粉水解和糖的消耗，从而促进了水稻种子在低温条件下的萌发。总之，低温下水稻种子中生物活性 GA 的缺乏导致淀粉水解和糖消耗减少，从而抑制了种子的萌发。
