Heat stress occurring at reproductive stages can result in significant and permanent damage to crop yields. However, previous genetic studies in understanding heat stress response and signaling were performed mostly on seedling and plants at early vegetative stages. Here we identify, using a developmentally defined, gain‐of‐function genetic screen with approximately 18 000 Arabidopsis thaliana activation‐tagged lines, a mutant that maintained productive seed set post‐severe heat stress during flowering. Genome walking indicated this phenotype was caused by the insertion of 35S enhancers adjacent to a nuclear localized transcription factor AtMYB68. Subsequent overexpression analysis confirmed that AtMYB68 was responsible for the reproductive heat tolerance of the mutant. Furthermore, these transgenic Arabidopsis plants exhibited enhanced abscisic acid sensitivity at and post‐germination, reduced transpirational water loss during a drought treatment, and enhanced seed yield under combined heat and drought stress during flowering. Ectopic expression of AtMYB68 in Brassica napus driven either by 35S or by heat‐inducible promoter recapitulated the enhanced reproductive heat stress and drought tolerance phenotypes observed in the transgenic Arabidopsis. The improvement to heat stress is likely due to enhanced pollen viability observed in the transgenic plants. More importantly, the transgenic canola showed significant yield advantages over the non‐transgenic controls in multiple locations, multiple season field trials under various drought and heat stress conditions. Together these results suggest that AtMYB68 regulate plant stress tolerance at the most important yield determining stage of plant development, and is an effective target for crop yield protection under current global climate volatility.

中文翻译：

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激活标签鉴定拟南芥转录因子AtMYB68在决定生殖阶段的耐热性和干旱性

生殖阶段发生的热应激可能会严重损害作物的产量。然而，先前的了解热应激反应和信号传导的遗传研究大多是在营养早期的幼苗和植物上进行的。在这里，我们利用发育定义的功能获得遗传筛选，鉴定了大约18000个拟南芥激活标记系，该突变体在开花过程中在严重热胁迫后仍能维持生产性种子。基因组行走表明该表型是由邻近核定位转录因子AtMYB68的35S增强子的插入引起的。随后的过表达分析确认AtMYB68负责突变体的生殖耐热性。此外，这些转基因拟南芥植物在发芽时和发芽后表现出增强的脱落酸敏感性，在干旱处理中减少了蒸腾作用的水分流失，并且在开花期间在高温和干旱胁迫的共同作用下提高了种子产量。AtMYB68在甘蓝型油菜中的异位表达在转基因拟南芥中观察到，由35S或由热诱导型启动子驱动的基因，再现了增强的生殖热胁迫和抗旱表型。热应激的改善可能是由于在转基因植物中观察到的花粉活力增强。更重要的是，在各种干旱和高温胁迫条件下的多个地点，多个季节的田间试验中，转基因双低油菜籽比非转基因双低油菜籽显示出显着的产量优势。这些结果共同表明，AtMYB68在植物发育的最重要的产量决定阶段调节植物的胁迫耐受性，并且是在当前全球气候波动下保护作物产量的有效目标。