R2R3-type MYBs are a key group of regulatory factors that control diverse developmental processes and stress tolerance in plants. Soybean is a major legume crop with the richness of seed protein and edible vegetable oil, and 244 R2R3-type MYBs have been identified in soybean. However, the knowledge regarding their functional roles has been greatly limited as yet. In this study, a novel R2R3-type MYB (GmMYB81) was functionally characterized in soybean, and it is closely related to two abiotic stress-associated regulators (AtMYB44 and AtMYB77). GmMYB81 transcripts not only differentially accumulated in soybean tissues and during embryo development, but also were significantly enhanced by drought, salt and cold stress. Histochemical GUS assay in Arabidopsis indicated that GmMYB81 promoter showed high activity in seedlings, rosette leaves, inflorescences, silique wall, mature anthers, roots, and germinating seeds. Further investigation indicated that over-expression of GmMYB81 in Arabidopsis caused auxin-associated phenotypes, including small flower and silique, more branch, and weakened apical dominance. Moreover, over-expression of GmMYB81 significantly elevated the rates of seed germination and green seedling under salt and drought stress, indicating that GmMYB81 might confer plant tolerance to salt and drought stress during seed germination. Additionally, protein interaction analysis showed that GmMYB81 interacts with the abiotic stress regulator GmSGF14l. Further observation indicated that they displayed similar expression patterns under drought and salt stress, suggesting GmMYB81 and GmSGF14l might cooperatively affect stress tolerance. These findings will facilitate future investigations of the regulatory mechanisms of GmMYB81 in response to plant stress tolerance, especially seed germination under abiotic stresses.

中文翻译：

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大豆R2R3-MYB转录因子GmMYB81的表征及其在非生物胁迫下的功能作用。

R2R3型MYB是控制植物中各种发育过程和胁迫耐受性的关键调控因子组。大豆是一种主要的豆类作物，种子蛋白和食用植物油丰富，在大豆中已鉴定出244种R2R3型MYB。但是，关于它们的功能角色的知识迄今仍然非常有限。在这项研究中，新型R2R3型MYB（GmMYB81）在大豆中具有功能特征，并且与两个非生物胁迫相关的调节剂（AtMYB44和AtMYB77）密切相关。GmMYB81转录本不仅在大豆组织中和胚胎发育过程中差异积累，而且在干旱，盐分和寒冷胁迫下均显着增强。拟南芥中的组织化学GUS分析表明，GmMYB81启动子在幼苗，莲座叶，花序，角果墙，成熟的花药，根和发芽种子。进一步的研究表明，拟南芥中GmMYB81的过度表达导致生长素相关的表型，包括小花和长角果，更多的分支，并削弱了顶端的优势。此外，在盐和干旱胁迫下，GmMYB81的过表达显着提高了种子发芽率和绿色幼苗的发芽率，表明GmMYB81可能在种子发芽过程中赋予植物对盐和干旱胁迫的耐受性。另外，蛋白质相互作用分析表明GmMYB81与非生物胁迫调节剂GmSGF14l相互作用。进一步的观察表明，它们在干旱和盐胁迫下表现出相似的表达模式，表明GmMYB81和GmSGF14l可能协同影响胁迫耐受性。