MYB transcription factors (TFs) have been reported to regulate the biosynthesis of secondary metabolites, as well as to mediate plant adaption to abiotic stresses, including drought. However, the roles of MYB TFs in regulating plant architecture and yield potential remain poorly understood. Here, we studied the roles of the dehydration‐inducible GmMYB14 gene in regulating plant architecture, high‐density yield and drought tolerance through the brassinosteroid (BR) pathway in soybean. GmMYB14 was shown to localize to nucleus and has a transactivation activity. Stable GmMYB14‐overexpressing (GmMYB14‐OX) transgenic soybean plants displayed a semi‐dwarfism and compact plant architecture associated with decreased cell size, resulting in a decrease in plant height, internode length, leaf area, leaf petiole length and leaf petiole angle, and improved yield in high density under field conditions. Results of the transcriptome sequencing suggested the involvement of BRs in regulating GmMYB14‐OX plant architecture. Indeed, GmMYB14‐OX plants showed reduced endogenous BR contents, while exogenous application of brassinolide could partly rescue the phenotype of GmMYB14‐OX plants. Furthermore, GmMYB14 was shown to directly bind to the promoter of GmBEN1 and up‐regulate its expression, leading to reduced BR content in GmMYB14‐OX plants. GmMYB14‐OX plants also displayed improved drought tolerance under field conditions. GmBEN1 expression was also up‐regulated in the leaves of GmMYB14‐OX plants under polyethylene glycol treatment, indicating that the GmBEN1‐mediated reduction in BR level under stress also contributed to drought/osmotic stress tolerance of the transgenic plants. Our findings provided a strategy for stably increasing high‐density yield and drought tolerance in soybean using a single TF‐encoding gene.

中文翻译：

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GmMYB14的过表达通过调节油菜素类固醇途径介导的植物结构提高大豆的高密度产量和耐旱性


据报道，MYB 转录因子 (TF) 可以调节次生代谢物的生物合成，并调节植物对非生物胁迫（包括干旱）的适应。然而，人们对 MYB 转录因子在调节植物结构和产量潜力方面的作用仍知之甚少。在这里，我们研究了大豆中脱水诱导的GmMYB14基因通过油菜素类固醇 (BR) 途径调节植物结构、高密度产量和耐旱性的作用。 GmMYB14 显示定位于细胞核并具有反式激活活性。稳定的GmMYB14-过表达（ GmMYB14-OX ）转基因大豆植株表现出半矮化和紧凑的植物结构，与细胞尺寸减小相关，导致株高、节间长度、叶面积、叶柄长度和叶柄角度减小，并且提高田间条件下高密度产量。转录组测序结果表明 BR 参与调节GmMYB14-OX植物结构。事实上， GmMYB14-OX植物表现出内源 BR 含量降低，而外源施用油菜素内酯可以部分挽救GmMYB14-OX植物的表型。此外，GmMYB14 被证明可以直接结合GmBEN1的启动子并上调其表达，导致GmMYB14-OX植物中 BR 含量减少。 GmMYB14-OX植物在田间条件下也表现出更好的耐旱性。 在聚乙二醇处理下， GmMYB14-OX植物的叶子中GmBEN1表达也上调，表明胁迫下GmBEN1介导的 BR 水平降低也有助于转基因植物的干旱/渗透胁迫耐受性。我们的研究结果提供了一种使用单一 TF 编码基因稳定提高大豆高密度产量和耐旱性的策略。