School of Food and Biological Engineering, Hefei University of Technology, Hefei, Anhui 230009, China.
Department of Plant Sciences, University of Idaho, Moscow, Idaho, 83844, USA.
J Exp Bot. 2023 Sep 29;74(18):5635-5652. doi: 10.1093/jxb/erad242.
Extensins are hydroxyproline-rich glycoproteins and generally play a structural role in cell wall integrity. In this study, we determined a novel role of tomato (Solanum lycopersicum) SENESCENCE-ASSOCIATED EXTENSIN1 (SAE1) in leaf senescence. Both gain- and loss-of-function analyses suggest that SAE1 plays a positive role in leaf senescence in tomato. Transgenic plants overexpressing SAE1 (SAE1-OX) exhibited premature leaf senescence and enhanced dark-induced senescence, whereas SAE1 knockout (SAE1-KO) plants displayed delayed development-dependent and dark-induced leaf senescence. Heterologous overexpression of SlSAE1 in Arabidopsis also led to premature leaf senescence and enhanced dark-induced senescence. In addition, the SAE1 protein was found to interact with the tomato ubiquitin ligase SlSINA4, and SlSINA4 promoted SAE1 degradation in a ligase-dependent manner when co-expressed in Nicotiana benthamiana leaves, suggesting that SlSINA4 controls SAE1 protein levels via the ubiquitin-proteasome pathway. Introduction of an SlSINA4-overexpression construct into the SAE1-OX tomato plants consistently completely eliminated accumulation of the SAE1 protein and suppressed the phenotypes conferred by overexpression of SAE1. Taken together, our results suggest that the tomato extensin SAE1 plays a positive role in leaf senescence and is regulated by the ubiquitin ligase SINA4.
伸展蛋白是富含羟脯氨酸的糖蛋白，通常在细胞壁完整性中起结构作用。在这项研究中，我们确定了番茄（Solanum lycopersicum）衰老相关伸展蛋白 1（SAE1）在叶片衰老中的一个新作用。功能获得和功能丧失分析都表明 SAE1 在番茄叶片衰老中起积极作用。过表达 SAE1 的转基因植物表现出过早的叶片衰老和增强的暗诱导衰老，而 SAE1 敲除（SAE1-KO）植物表现出延迟的发育依赖性和暗诱导的叶片衰老。在拟南芥中异源过表达 SlSAE1 也导致过早的叶片衰老和增强的暗诱导衰老。此外，发现 SAE1 蛋白与番茄泛素连接酶 SlSINA4 相互作用，并且当在烟草叶片中共表达时，SlSINA4 以依赖连接酶的方式促进 SAE1 降解，表明 SlSINA4 通过泛素-蛋白酶体途径控制 SAE1 蛋白水平。将 SlSINA4 过表达构建体引入 SAE1-OX 番茄植物中，始终完全消除了 SAE1 蛋白的积累，并抑制了 SAE1 过表达赋予的表型。总之，我们的结果表明，番茄伸展蛋白 SAE1 在叶片衰老中起积极作用，并受泛素连接酶 SINA4 的调节。
