Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China.
Key Laboratory of Crop Ecology and Molecular Physiology (Fujian Agriculture and Forestry University), Fujian Province Universities, Fuzhou, 350002, People's Republic of China.
Plant Cell Rep. 2018 Jul;37(7):981-992. doi: 10.1007/s00299-018-2282-9. Epub 2018 Mar 24.
DELLA proteins' negative regulation of dark-induced senescence and chlorophyll degradation in Arabidopsis is through interaction with WRKY6 and thus repression of its transcriptional activities on senescence-related genes. Senescence is an intricate and highly orchestrated process regulated by numerous endogenous and environmental signals. Gibberellins (GAs) and their signaling components DELLA proteins have been known to participate in the regulation of senescence. However, the mechanism of the GA-DELLA system involved in the senescence process remains largely unclear. Darkness is a known environmental factor that induces plant senescence. In this study, exogenous GA (an active form of GA) accelerated but paclobutrazol (a specific GA biosynthesis inhibitor) retarded dark-induced leaf yellowing in Arabidopsis. Moreover, the dark-triggered decrease in chlorophyll content, increase in cell membrane leakage, and upregulation of senescence-associated genes were notably impaired in both endogenous GA-decreased mutants ga3ox1/ga3ox2 and ga20ox1/ga20ox2 compared with those in wild-type Col-0. These effects of darkness were enhanced in the quintuple mutant of DELLA genes gai-t6/rga-t2/rgl1-1/rgl2-1/rgl3-1 and conversely attenuated in the gain-of-function mutant gai and transgenic plant 35S::TAP-RGAd17 compared with wild-type Ler. Subsequently, RGA interacted with the transcription factor WRKY6 in a yeast two-hybrid assay, as confirmed by bimolecular fluorescence complementation and pull-down analyses. In addition, mutation and overexpression of WRKY6 retarded and accelerated dark-induced senescence, respectively. Furthermore, transient expression assays in Arabidopsis protoplasts indicated that RGA and GAI weakened the transcriptional activities of WRKY6 on its downstream senescence-related genes, including SAG13 and SGR. Taken together, these results suggest that GAs positively and DELLAs negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis. DELLAs function in this process, at least in part, by interacting with WRKY6.
DELLA 蛋白通过与 WRKY6 相互作用，抑制其对衰老相关基因的转录活性，从而负调控拟南芥黑暗诱导的衰老和叶绿素降解。衰老是一个复杂而高度协调的过程，受许多内源性和环境信号的调控。赤霉素（GA）及其信号成分 DELLA 蛋白已被证明参与衰老的调控。然而，GA-DELLA 系统参与衰老过程的机制在很大程度上仍不清楚。黑暗是一种已知的环境因子，能诱导植物衰老。在本研究中，外源 GA（GA 的一种活性形式）加速了，但多效唑（一种特定的 GA 生物合成抑制剂）延缓了拟南芥黑暗诱导的叶片黄化。此外，与野生型 Col-0 相比，内源 GA 减少突变体 ga3ox1/ga3ox2 和 ga20ox1/ga20ox2 中黑暗触发的叶绿素含量下降、细胞膜渗漏增加和衰老相关基因上调明显受损。DELLA 基因 gai-t6/rga-t2/rgl1-1/rgl2-1/rgl3-1 的五重突变体增强了黑暗的这些作用，而 gai 的功能获得突变体和 35S::TAP-RGAd17 的转基因植物则减弱了这些作用。随后，RGA 在酵母双杂交实验中与转录因子 WRKY6 相互作用，双分子荧光互补和下拉分析证实了这一点。此外，WRKY6 的突变和过表达分别延缓和加速了黑暗诱导的衰老。此外，在拟南芥原生质体中的瞬时表达实验表明，RGA 和 GAI 减弱了 WRKY6 对其下游衰老相关基因，包括 SAG13 和 SGR 的转录活性。综上所述，这些结果表明，GA 正向调控，DELLA 负向调控拟南芥黑暗诱导的衰老和叶绿素降解。DELLA 蛋白在这个过程中起作用，至少部分是通过与 WRKY6 相互作用。
