Key Laboratory of Application and Safety Control of Genetically Modified Crops, College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China.
Key Laboratory of Application and Safety Control of Genetically Modified Crops, College of Agronomy and Biotechnology, Southwest University, Chongqing 400715, China.
Mol Plant. 2023 May 1;16(5):829-848. doi: 10.1016/j.molp.2023.03.008. Epub 2023 Mar 15.
Multiple enzymes perform moonlighting functions distinct from their main roles. UDP-glucose epimerases (UGEs), a subclass of isomerases, catalyze the interconversion of UDP-glucose (UDP-Glc) and UDP-galactose (UDP-Gal). We identified a rice male-sterile mutant, osuge1, with delayed tapetum degradation and abortive pollen. The mutant osuge1 protein lacked UDP-glucose epimerase activity, resulting in higher UDP-Gal content and lower UDP-Glc levels in the osuge1 mutant compared with the wild type. Interestingly, we discovered that OsUGE1 participates in the TIP2/bHLH142-TDR-EAT1/DTD transcriptional regulatory cascade involved in tapetum degradation, in which TIP2 and TDR regulate the expression of OsUGE1 while OsUGE1 regulates the expression of EAT1. In addition, we found that OsUGE1 regulates the expression of its own gene by directly binding to an E-box element in the OsUGE1 promoter. Collectively, our results indicate that OsUGE1 not only functions as a UDP-glucose epimerase but also moonlights as a transcriptional activator to promote tapetum degradation, revealing a novel regulatory mechanism of rice reproductive development.
多种酶具有与其主要功能不同的分子伴侣功能。UDP-葡萄糖差向异构酶（UGEs）是异构酶的一个亚类，可催化 UDP-葡萄糖（UDP-Glc）和 UDP-半乳糖（UDP-Gal）的相互转化。我们鉴定了一个水稻雄性不育突变体 osuge1，其花粉败育且绒毡层降解延迟。该突变体 osuge1 蛋白缺乏 UDP-葡萄糖差向异构酶活性，导致与野生型相比，osuge1 突变体中 UDP-Gal 含量更高，UDP-Glc 水平更低。有趣的是，我们发现 OsUGE1 参与了与绒毡层降解有关的 TIP2/bHLH142-TDR-EAT1/DTD 转录调控级联反应，其中 TIP2 和 TDR 调控 OsUGE1 的表达，而 OsUGE1 则调控 EAT1 的表达。此外，我们发现 OsUGE1 通过直接结合 OsUGE1 启动子中的 E 盒元件来调节自身基因的表达。总之，我们的研究结果表明，OsUGE1 不仅作为 UDP-葡萄糖差向异构酶发挥作用，还作为转录激活因子发挥作用以促进绒毡层降解，揭示了水稻生殖发育的一种新的调控机制。
