SummaryRegulation of grain size is a crucial strategy for improving the crop yield and is also a fundamental aspect of developmental biology. However, the underlying molecular mechanisms governing grain development in wheat remain largely unknown. In this study, we identified a wheat atypical basic helix–loop–helix (bHLH) transcription factor, TabHLH489, which is tightly associated with grain length through genome‐wide association study and map‐based cloning. Knockout of TabHLH489 and its homologous genes resulted in increased grain length and weight, whereas the overexpression led to decreased grain length and weight. TaSnRK1α1, the α‐catalytic subunit of plant energy sensor SnRK1, interacted with and phosphorylated TabHLH489 to induce its degradation, thereby promoting wheat grain development. Sugar treatment induced TaSnRK1α1 protein accumulation while reducing TabHLH489 protein levels. Moreover, brassinosteroid (BR) promotes grain development by decreasing TabHLH489 expression through the transcription factor BRASSINAZOLE RESISTANT1 (BZR1). Importantly, natural variations in the promoter region of TabHLH489 affect the TaBZR1 binding ability, thereby influencing TabHLH489 expression. Taken together, our findings reveal that the TaSnRK1α1‐TabHLH489 regulatory module integrates BR and sugar signalling to regulate grain length, presenting potential targets for enhancing grain size in wheat.

中文翻译：

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TaSnRK1-TabHLH489 模块集成油菜素类固醇和糖信号传导来调节面包小麦的籽粒长度

摘要 颗粒大小的调节是提高作物产量的关键策略，也是发育生物学的一个基本方面。然而，控制小麦籽粒发育的潜在分子机制仍然很大程度上未知。在这项研究中，我们通过全基因组关联研究和基于图位的克隆，鉴定了一种小麦非典型碱性螺旋-环-螺旋（bHLH）转录因子TabHLH489，它与籽粒长度密切相关。淘汰赛TabHLH489其同源基因导致籽粒长度和重量增加，而过表达则导致籽粒长度和重量减少。TaSnRK1α1是植物能量传感器SnRK1的α催化亚基，与TabHLH489相互作用并磷酸化，诱导其降解，从而促进小麦籽粒发育。糖处理诱导 TaSnRK1α1 蛋白积累，同时降低 TabHLH489 蛋白水平。此外，油菜素类固醇（BR）通过减少TabHLH489通过转录因子 BRASSINAZOLE RESISTANT1 (BZR1) 表达。重要的是，启动子区域的自然变异TabHLH489影响TaBZR1结合能力，从而影响TabHLH489表达。综上所述，我们的研究结果表明，TaSnRK1α1-TabHLH489 调控模块整合 BR 和糖信号来调节籽粒长度，为提高小麦籽粒大小提供了潜在的目标。