Ubiquitination plays important roles in modulating the abiotic stress tolerance of plants. Drought seriously restricts agricultural production, but how ubiquitination participates in regulating drought tolerance remains largely unknown. Here, we identified a drought-inducible gene, MYB30-INTERACTING E3 LIGASE 1 (GhMIEL1), which encodes a RING E3 ubiquitin ligase in cotton (Gossypium hirsutum). GhMIEL1 was strongly induced by polyethylene glycol (PEG-6000) and the phytohormone abscisic acid (ABA). Overexpression and knockdown of GhMIEL1 in cotton substantially enhanced and reduced drought tolerance, respectively. GhMIEL1 interacted with the MYB transcription factor GhMYB66 and could ubiquitinate and degrade it in vitro. GhMYB66 directly bound to the LONELY GUY 5 (GhLOG5) promoter, a gene encoding cytokinin riboside 5'-monophosphate phosphoribohydrolase, to repress its transcription. Overexpression of GhMIEL1 and silencing of GhMYB66 altered the homeostasis of cytokinin of plant roots, increased total root length and number of root tips, and enhanced plant drought tolerance. Conversely, silencing GhLOG5 decreased total root length and number of root tips and reduced plant drought tolerance. Our studies reveal that the GhMIEL1-GhMYB66-GhLOG5 module positively regulates drought tolerance in cotton, which deepens our understanding of plant ubiquitination-mediated drought tolerance and provides insights for improving drought tolerance.

中文翻译：

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MYB30 相互作用的 E3 连接酶 1 调节 LONELY GUY 5 介导的细胞分裂素代谢，促进棉花的耐旱性


泛素化在调节植物的非生物胁迫耐受性中起着重要作用。干旱严重限制了农业生产，但泛素化如何参与调节耐旱性在很大程度上仍然未知。在这里，我们鉴定了一个干旱诱导基因，MYB30 相互作用的 E3 连接酶 1 （GhMIEL1），它编码棉花 （Gossypium hirsutum） 中的 RING E3 泛素连接酶。GhMIEL1 受聚乙二醇 （PEG-6000） 和植物激素脱落酸 （ABA） 的强烈诱导。棉花中 GhMIEL1 的过表达和敲低分别显著增强和降低了耐旱性。GhMIEL1 与 MYB 转录因子 GhMYB66 相互作用，可在体外泛素化和降解。GhMYB66 直接与 LONELY GUY 5 （GhLOG5） 启动子结合，该启动子是编码细胞分裂素核糖苷 5'-单磷酸磷酸水解酶的基因，以抑制其转录。过表达 GhMIEL1 和 沉默 GhMYB66 改变了植物根系细胞分裂素的稳态，增加了总根长和根尖数，增强了植物耐旱性。相反，沉默 GhLOG5 减少了总根长和根尖数量，并降低了植物的耐旱性。我们的研究表明，GhMIEL1-GhMYB66-GhLOG5 模块正向调节棉花的耐旱性，这加深了我们对植物泛素化介导的耐旱性的理解，并为提高耐旱性提供了见解。