Promoting seed germination after short episodes of heat stress during the wheat grain filling stage is a serious problem that results in pre-harvest sprouting. The plant hormones abscisic acid (ABA), gibberellins (GAs), and ethylene (ETH) are well known to be involved in germination control. However, the genes associated with the metabolism and responsiveness of these hormones to heat stress during wheat grain filling are not well understood. Transcriptomic analysis was carried out to explore the mechanisms controlling seed germination under five days (15–20 days after flowering, DAF) of heat stress (20, 24, 28, and 32°C) in wheat grains at 15–30 DAF using comparative RNA sequencing. A dataset of 2073 differentially regulated genes was used to help elucidate the molecular mechanisms that respond to heat stress and affect seed germination in wheat. Some genes related to ABA, GA, and ETH biosynthesis, transport, and signaling had significantly different expression levels under heat stress. Among these genes, the transcriptional alterations of plant hormone-related genes, such as NCED9, AAO3, CYP707A2, GA20ox, and SAM1 uncovered here, provide a foundation for identifying key players involved in determining seed dormancy and germination. The expression levels of many germination-related genes did not linearly increase with increasing temperature. In this study, 28°C is a threshold of temperature tolerance during the grain filling stage. Heat stress, especially extremely high temperature (>28°C), represses ABA-related gene expression and promotes seed germination.

中文翻译：

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时间转录组揭示了小麦籽粒灌浆过程中热应激对种子萌发的影响

在小麦籽粒灌浆期短暂热应激后促进种子萌发是导致收获前发芽的严重问题。众所周知，植物激素脱落酸 (ABA)、赤霉素 (GAs) 和乙烯 (ETH) 都参与了发芽控制。然而，与这些激素在小麦籽粒灌浆过程中的代谢和对热应激的反应相关的基因尚不清楚。进行转录组学分析以探索在 15-30 DAF 小麦籽粒热应激（20、24、28 和 32°C）的 5 天（开花后 15-20 天，DAF）下控制种子萌发的机制，使用比较方法RNA测序。2073 个差异调控基因的数据集用于帮助阐明小麦对热应激反应和影响种子萌发的分子机制。一些与 ABA、GA 和 ETH 生物合成、转运和信号传导相关的基因在热应激下的表达水平存在显着差异。在这些基因中，植物激素相关基因的转录改变，如此处发现的NCED9、AAO3、CYP707A2、GA20ox和SAM1为确定参与确定种子休眠和发芽的关键参与者提供了基础。许多发芽相关基因的表达水平并没有随着温度的升高而线性增加。在本研究中，28°C 是籽粒灌浆阶段的温度耐受阈值。热应激，尤其是极高的温度（>28°C），会抑制 ABA 相关基因的表达并促进种子萌发。