Plant senescence is a highly coordinated process during which leaf cells undergo active degenerative processes. WRKY transcription factors have been suggested to participate in the regulation of leaf senescence, but the related signaling pathways and physiological mechanisms remain unclear.
Prof. YU Diqiu and his team from Xishuangbanna Tropical Botanical Garden (XTBG) used a molecular and genetic approach to investigate the role of Arabidopsis thaliana WRKY DNA binding protein 45 (WRKY45) in age-triggered leaf senescence.
Analysis of WRKY45 expression showed that WRKY45 is a senescence-responsive gene. It functioned as a senescence-associated gene (SAG) to regulate and fine-tune the complex signaling and transcriptional networks that mediate plant senescence. Altered WRKY45 expression affected gibberellin (GA)-regulated leaf senescence.
The researchers further found that constitutive over-expression of WRKY45 led to accelerated leaf senescence in transgenic plants. WRKY45 acts as a transcriptional activator to transmit GA-mediated leaf senescence signals.
Chromatin immunoprecipitation experiments revealed that WRKY45 directly binds to the promoter of several SENESCENCE-ASSOCIATED GENEs, such as SAG12, SAG13, SAG113 and SEN4.
In vivo and in vitro experiments revealed that REPRESSOR OF 93 ga1-3 (RGA)-LIKE 1 (RGL1) physically interacts with WRKY45 and represses its activation ability, and that overexpression of RGL1 significantly represses age-triggered leaf senescence.
The results demonstrated that WRKY45 functions as a component of the regulatory network that integrates age and GA signaling to modulate the onset and progression of leaf senescence.
The study entitled “Arabidopsis WRKY45 interacts with the DELLA protein RGL1 to positively regulate age-triggered leaf senescence” has been published online in Molecular Plant.
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