The WRKY transcription factors (TFs) play multifaceted roles in plant growth, development, and stress response. Previously, we found that SlWKRY81 negatively regulates tomato tolerance to drought; however, the mechanisms of stomatal regulation in response to drought remain largely unclear. Here, we showed that drought-induced upregulation in the SlWKRY81 transcripts induced photoinhibition and reduced the net photosynthetic rate in tomato leaves. However, silencing SlWKRY81 alleviated those inhibitions and minimized the drought-induced damage. A time-course of water loss showed that SlWKRY81 silencing significantly and consistently reduced leaf water loss, suggesting a role for SlWKRY81 in stomatal movement. Further analysis using light microscopy revealed that SlWKRY81 silencing significantly decreased stomatal aperture and increased the ratio of length to width of stomata under drought. Both biochemical assay and confocal laser scanning microscopy demonstrated that drought-induced upregulation in SlWKRY81 expression inhibited the nitric oxide (NO) accumulation in the guard cells, which was attributed to the simultaneous declines in the activity of NITRATE REDUCTASE (NR) and NR expression in tomato leaves. The inspection of 3-kb sequences upstream of the predicted translational start site of the NR identified three copies of the core W-box (TTGACC/T) sequence in the promoter region, indicating possible targets of SlWRKY81. Taken together, these data suggest that SlWRKY81 potentially represses NR transcription and thus reduces NO accumulation to attenuate stomatal closure and subsequent drought tolerance. These findings provide an improved understanding of the mechanisms of WRKY-induced regulation of stomatal closure, which can be exploited in the future to enhance drought tolerance in crops. This article is protected by copyright. All rights reserved.

中文翻译：

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SlWRKY81转录因子通过减弱干旱下番茄保卫细胞中一氧化氮的积累来抑制气孔关闭

WRKY 转录因子 (TF) 在植物生长、发育和胁迫反应中发挥着多方面的作用。此前，我们发现 SlWKRY81 负调控番茄对干旱的耐受性；然而，响应干旱的气孔调节机制在很大程度上仍不清楚。在这里，我们发现干旱诱导的 SlWKRY81 转录物上调诱导了光抑制并降低了番茄叶片的净光合速率。然而，沉默 SlWKRY81 减轻了这些抑制并最大限度地减少了干旱引起的损害。水分流失的时间过程表明，SlWKRY81 沉默显着且持续减少叶片水分流失，表明 SlWKRY81 在气孔运动中的作用。使用光学显微镜进行的进一步分析表明，在干旱条件下，SlWKRY81 沉默显着降低了气孔孔径并增加了气孔的长宽比。生化分析和共聚焦激光扫描显微镜均表明，干旱诱导的 SlWKRY81 表达上调抑制了保卫细胞中一氧化氮（NO）的积累，这归因于硝酸还原酶（NR）和 NR 表达的活性同时下降。番茄叶。检查 NR 预测的翻译起始位点上游的 3-kb 序列确定了启动子区域中核心 W-box (TTGACC/T) 序列的三个拷贝，表明 SlWRKY81 的可能目标。综合起来，这些数据表明，SlWRKY81 可能抑制 NR 转录，从而减少 NO 积累，从而减弱气孔关闭和随后的耐旱性。这些发现提供了对 WRKY 诱导的气孔关闭调节机制的更好理解，未来可用于提高作物的耐旱性。本文受版权保护。版权所有。