Drought is one of the most critical abiotic stresses that threaten crop production worldwide. This stress affects the rice crop in all stages of rice development; however, the occurrence during reproductive and grain-filling stages has the most impact on grain yield. Although many global transcriptomic studies have been performed during the reproductive stage in rice, very limited information is available for the grain-filling stage. Hence, we intend to investigate how the rice plant responds to drought stress during the grain-filling stage and how the responses change over time under field conditions. Two rice genotypes were selected for RNA-seq analysis: ‘4610’, previously reported as a moderately tolerant breeding line, and Rondo, an elite indica rice cultivar susceptible to drought conditions. Additionally, 10 agronomic traits were evaluated under normal irrigated and drought conditions. Leaf tissues were collected during grain-filling stages at two time points, 14 and 21 days after the drought treatment, from both the drought field and normal irrigated field conditions. Based on agronomic performances, ‘4610’ was less negatively affected than Rondo under mild drought conditions, and expression profiling largely aligned with the phenotypic data. The transcriptomic data indicated that, in general, ‘4610’ had much earlier responses than its counterpart in mitigating the impact of drought stress. Several key genes and gene families related to drought stress or stress-related conditions were found differentially expressed in this study, including transcription factors, drought tolerance genes and reactive oxygen species scavengers. Furthermore, this study identified novel differentially expressed genes (DEGs) without function annotations that may play roles in drought tolerance-related functions. Some of the important DEGs detected in this study can be targeted for future research.

中文翻译：

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灌浆期轻度田间干旱胁迫下两种水稻基因型的转录组分析

干旱是威胁全球作物生产的最严重的非生物胁迫之一。这种胁迫会影响水稻发育各个阶段的水稻作物；然而，生育期和灌浆期的发生对粮食产量的影响最大。尽管已经在水稻的生殖阶段进行了许多全球转录组学研究，但可用于灌浆阶段的信息非常有限。因此，我们打算研究水稻在灌浆期如何响应干旱胁迫，以及在田间条件下响应如何随时间变化。选择了两种水稻基因型进行 RNA-seq 分析：“4610”，以前被报道为中等耐受性育种系，以及 Rondo，一种易受干旱条件影响的优良籼稻品种。此外，在正常灌溉和干旱条件下评估了 10 个农艺性状。在干旱处理后的 14 天和 21 天两个时间点，从干旱田地和正常灌溉田地条件下，在灌浆期收集叶组织。基于农艺性能，在轻度干旱条件下，'4610' 受到的负面影响小于 Rondo，并且表达谱与表型数据基本一致。转录组数据表明，一般而言，“4610”在减轻干旱胁迫影响方面的反应比其对应物早得多。本研究发现与干旱胁迫或胁迫相关条件相关的几个关键基因和基因家族存在差异表达，包括转录因子、耐旱基因和活性氧清除剂。此外，该研究确定了新的差异表达基因（DEGs），没有功能注释，可能在耐旱相关功能中发挥作用。本研究中检测到的一些重要的 DEG 可以作为未来研究的目标。