Huang Yutao, Mei Gaofu, Cao Dongdong, Qin Yebo, Yang Liu, Ruan Xiaoli
Institute of Crop and Nuclear Technology Utilization, Zhejiang Academy of Agricultural Sciences, Hangzhou, China.
Zhejiang Agricultural Technology Extension Center, Hangzhou, China.
Front Plant Sci. 2023 Sep 18;14:1230331. doi: 10.3389/fpls.2023.1230331. eCollection 2023.
Heat stress is a vital factor which restricts rice seed quality and yield. However, the response mechanism to heat stress in the mid filling stage of rice seed is unclear.
In the present study we integrated phenotypic analysis with biochemical, hormone, and gene expression analysis in order to explore technologies for improving rice seeds heat tolerance and subsequent seed germination.
Spermidine (Spd) application effectively alleviated the damage of heat stress treatment during mid-filling stage (HTM, 12-20 days after pollination) on seed development, promoted subsequent seed germination and seedlings establishment. Spd significantly increased seed dry weight, starch and amylose contents during seed development under heat stress, and improved seed germinate, seedlings establishment and seedling characteristics during germination time. Biochemical analysis indicated that, HTM significantly decreased the activities of several starch synthase enzymes and led to a decrease in starch content. While Spd treatment significantly enhanced the activities of ADP-glucose pyrophosphorylas and granule-bound starch synthase, as well as the corresponding-genes expressions in HTM rice seeds, resulting in the increases of amylose and total starch contents. In addition, Spd significantly increased the catalase and glutathione reductase activities together with corresponding-genes expressions, and lowered the overaccumulation of H2O2 and malondialdehyde in HTM seeds. In the subsequent seed germination process, HTM+Spd seeds exhibited dramatically up-regulated levels of soluble sugars, glucose, ATP and energy charges. Consistently, HTM+Spd seeds showed significantly increased of α-amylose and α-glucosidase activities as well as corresponding-genes expressions during early germination. Moreover, HTM evidently increased the abscisic acid (ABA) content, decreased the gibberellin (GA) content, and accordingly significantly declined the GA/ABA ratio during early rice seeds germination. However, Spd treatment did not significantly affect the metabolism of GA and ABA in seed germination stage.
The present study suggested that Spd treatment could effectively alleviate the negative impact of HTM on seed development and the subsequent seed germination, which might be closely correlated with starch synthesis and antioxidant defense during seed filling period, starch decomposition and energy supply in seed germination period.
热胁迫是限制水稻种子品质和产量的重要因素。然而，水稻种子灌浆中期对热胁迫的响应机制尚不清楚。
在本研究中，我们将表型分析与生化、激素和基因表达分析相结合，以探索提高水稻种子耐热性及后续种子萌发的技术。
施用亚精胺（Spd）有效减轻了灌浆中期（授粉后12 - 20天的热胁迫处理，HTM）对种子发育的损害，促进了后续种子萌发和幼苗建立。在热胁迫下，Spd显著增加了种子发育过程中的种子干重、淀粉和直链淀粉含量，并改善了种子萌发期间的种子萌发、幼苗建立和幼苗特性。生化分析表明，HTM显著降低了几种淀粉合成酶的活性，导致淀粉含量下降。而Spd处理显著增强了HTM水稻种子中ADP - 葡萄糖焦磷酸化酶和颗粒结合淀粉合成酶的活性以及相应基因的表达，导致直链淀粉和总淀粉含量增加。此外，Spd显著增加了过氧化氢酶和谷胱甘肽还原酶的活性以及相应基因的表达，并降低了HTM种子中H2O2和丙二醛的过度积累。在随后的种子萌发过程中，HTM + Spd种子的可溶性糖、葡萄糖、ATP和能量电荷水平显著上调。一致地，HTM + Spd种子在早期萌发期间α - 淀粉酶和α - 葡萄糖苷酶活性以及相应基因的表达显著增加。此外，HTM明显增加了脱落酸（ABA）含量，降低了赤霉素（GA）含量，因此在水稻种子早期萌发期间GA/ABA比值显著下降。然而，Spd处理在种子萌发阶段对GA和ABA的代谢没有显著影响。
本研究表明，Spd处理可以有效减轻HTM对种子发育和后续种子萌发的负面影响，这可能与种子灌浆期的淀粉合成和抗氧化防御、种子萌发期的淀粉分解和能量供应密切相关。
