DELLA proteins negatively regulate dark-induced senescence and chlorophyll degradation in Arabidopsis through interaction with the transcription factor WRKY6
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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 GA3 (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.
KeywordsArabidopsis Chlorophyll degradation Dark DELLA Gibberellins Senescence
Bimolecular fluorescence complementation
Non-yellow coloring 1
Real-time quantitative reverse transcription polymerase chain reaction
- REN LUC
Repressor of ga1-3
We would like to thank Dr. Peter Hedden for providing ga20ox1/ga20ox2 seeds, Dr. Nicholas P. Harberd for providing gai seeds, Dr. Xing-Wang Deng for providing 35S::TAP-RGAd17 seeds, Dr. Imre E. Somssich and Dr. Yi-Fang Chen for providing wrky6-1 and WRKY6OX seeds, and ABRC for providing della and ga3ox1/ga3ox2 seeds. This work was supported by National Natural Science Foundation of China (31701985 and 31700256), Natural Science Foundation of Fujian Province, China (2017J01611) and Fujian-Taiwan Joint Innovative Centre for Germplasm Resources and Cultivation of Crop (grant No. 2015-75. Fujian 2011 Program, China).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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