Abstract Seed germination is a key phase of the plant life cycle, and the plant is highly sensitive to low temperature during this phase. However, the physiological and molecular mechanisms underlying the adaptation of rice seeds to low temperatures remain elusive. The present study compared seed germination between Dongdao-4 and Jigeng-88 and investigated the mechanisms of their response to low temperature conditions. Seed germination percentage of Dongdao-4 was significantly higher than that of Jigeng-88 when exposed to low temperature. Furthermore, Dongdao-4 seeds exhibited higher concentrations of bioactive gibberellins (GA1 and GA4) under low temperature conditions compared to Jigeng-88 seeds, which was attributed to a higher induction of the expression of GA biosynthetic genes and a lower induction of the expression of GA inactivation genes at the transcriptional level in Dongdao-4 compared to those in Jigeng-88 seeds. We further demonstrated that GA treatment promoted seed germination under low temperature conditions, and GA biosynthetic inhibitors inhibited germination. During seed germination, soluble sugars are converted from starch by α-amylase to provide energy and fuel embryo development. The reduction in the germination percentage is accompanied by a reduction in α-amylase activity and soluble sugar concentrations under low temperature conditions. We observed higher α-amylase activity and soluble sugar levels in Dongdao-4 than in Jigeng-88 seeds under low temperature conditions. More soluble sugars were transported to embryos in Dongdao-4 seeds than in Jigeng-88 seeds under low temperature conditions, which was attributed to a higher transcriptional level of sugar transporters in Dongdao-4 than that in Jigeng-88. Abscisic acid (ABA) acts antagonistically compared to GA during seed germination. Lower endogenous concentrations of ABA in Dongdao-4 compared to those in Jigeng-88 seeds were found, because of the much higher transcriptional levels of ABA catabolism genes in Dongdao-4 than Jigeng-88 seeds when they were treated at an identical low temperature. These results suggest that the higher accumulation of endogenous bioactive GAs and soluble sugars and lower ABA concentrations in Dongdao-4 than Jigeng-88 were responsible for its increased seed germination under low temperature conditions.

中文翻译：

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两种不同耐低温水稻基因型种子萌发对比研究

摘要 种子萌发是植物生命周期的关键阶段，该阶段植物对低温高度敏感。然而，水稻种子适应低温的生理和分子机制仍然难以捉摸。本研究比较了东道4号和冀庚88号的种子萌发情况，并研究了它们对低温条件的响应机制。低温条件下，东道4号种子发芽率显着高于冀庚88号。此外，与冀庚 88 种子相比，东道 4 号种子在低温条件下表现出更高浓度的生物活性赤霉素（GA1 和 GA4），这归因于与冀庚88种子相比，东道4号在转录水平上对GA生物合成基因表达的更高诱导和对GA失活基因表达的更低诱导。我们进一步证明 GA 处理促进了低温条件下的种子萌发，而 GA 生物合成抑制剂抑制了种子的萌发。在种子萌发过程中，α-淀粉酶将淀粉转化为可溶性糖，为胚胎发育提供能量和燃料。在低温条件下，发芽率的降低伴随着α-淀粉酶活性和可溶性糖浓度的降低。我们在低温条件下观察到东道 4 号种子的 α-淀粉酶活性和可溶性糖含量高于冀庚 88 号种子。低温条件下，东道4号种子比冀庚88号种子向胚转运的可溶性糖更多，这归因于东道4号的糖转运蛋白转录水平高于冀庚88号。与 GA 相比，脱落酸 (ABA) 在种子萌发过程中起拮抗作用。发现东道4号中ABA的内源浓度低于冀庚88号，这是因为东道4号中ABA分解代谢基因的转录水平远高于在相同低温下处理的冀庚88号种子。这些结果表明，东道 4 号中内源性生物活性 GA 和可溶性糖的积累量高于吉庚 88 号，其 ABA 浓度低于吉庚 88 号是其在低温条件下种子萌发增加的原因。