A WRKY transcription factor, TaWRKY42-B, facilitates initiation of leaf senescence by promoting jasmonic acid biosynthesis

Ming-Ming Zhao,Xiao-Wen Zhang,Yong-Wei Liu,Shuo Zhou,Ke Li,Geng Wang,Qi Tan,Chun-Jiang Zhou

doi:10.1186/s12870-020-02650-7

Ming-Ming Zhao, Xiao-Wen Zhang + Show 6 more

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https://doi.org/10.1186/s12870-020-02650-7

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Abstract

BackgroundLeaf senescence comprises numerous cooperative events, integrates environmental signals with age-dependent developmental cues, and coordinates the multifaceted deterioration and source-to-sink allocation of nutrients. In crops, leaf senescence has long been regarded as an essential developmental stage for productivity and quality, whereas functional characterization of candidate genes involved in the regulation of leaf senescence has, thus far, been limited in wheat.ResultsIn this study, we analyzed the expression profiles of 97 WRKY transcription factors (TFs) throughout the progression of leaf senescence in wheat and subsequently isolated a potential regulator of leaf senescence, TaWRKY42-B, for further functional investigation. By phenotypic and physiological analyses in TaWRKY42-B-overexpressing Arabidopsis plants and TaWRKY42-B-silenced wheat plants, we confirmed the positive role of TaWRKY42-B in the initiation of developmental and dark-induced leaf senescence. Furthermore, our results revealed that TaWRKY42-B promotes leaf senescence mainly by interacting with a JA biosynthesis gene, AtLOX3, and its ortholog, TaLOX3, which consequently contributes to the accumulation of JA content. In the present study, we also demonstrated that TaWRKY42-B was functionally conserved with AtWRKY53 in the initiation of age-dependent leaf senescence.ConclusionOur results revealed a novel positive regulator of leaf senescence, TaWRKY42-B, which mediates JA-related leaf senescence via activation of JA biosynthesis and has the potential to be a target gene for molecular breeding in wheat.

Highlights

Leaf senescence comprises numerous cooperative events, integrates environmental signals with agedependent developmental cues, and coordinates the multifaceted deterioration and source-to-sink allocation of nutrients
TaWRKY42-B is downregulated during leaf senescence To identify candidate genes in the regulation of leaf senescence in T. aestivum, we conducted an RNA-seq experiment at four developmental stages of flag leaves (YL, young leaves; ML, mature leaves; ES, early senescent leaves; LS, late senescent leaves)
We identified 32 up-regulated WRKYs and 65 down-regulated WRKYs compared with young leaf stage (|log2(fold change)| ≥1;P < 0.05) (Fig. 1a-b)

Summary

Introduction

Leaf senescence comprises numerous cooperative events, integrates environmental signals with agedependent developmental cues, and coordinates the multifaceted deterioration and source-to-sink allocation of nutrients. Leaf senescence is a highly integrated developmental stage that coordinates multidimensional alterations at the physiological and molecular level [1]. Intracellular organelles and macro-molecules are dismantled and degenerated, which predominantly contributes to the source-to-sink allocation of nutrients [2]. The redistribution of nutrients from senescent organs to vegetative tissues is essential for plant fitness and critical for productivity and quality in crops [3, 4]. The initiation of leaf senescence is age-dependent and triggered by developmental cues [5]. When plants encounter abiotic and biotic stresses, the initiation of senescence will be accelerated [5, 18]

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