Abstract

Leaf senescence is an integral part of plant development aiming at the remobilization of nutrients and minerals out of the senescing tissue into developing parts of the plant. Sequential as well as monocarpic senescence maximize the usage of nitrogen, mineral, and carbon resources for plant growth and the sake of the next generation. However, stress-induced premature senescence functions as an exit strategy to guarantee offspring under long-lasting unfavorable conditions. In order to coordinate this complex developmental program with all kinds of environmental input signals, complex regulatory cues have to be in place. Major changes in the transcriptome imply important roles for transcription factors. Among all transcription factor families in plants, the NAC and WRKY factors appear to play central roles in senescence regulation. In this review, we summarize the current knowledge on the role of WRKY factors with a special focus on WRKY53. In contrast to a holistic multi-omics view we want to exemplify the complexity of the network structure by summarizing the multilayer regulation of WRKY53 of Arabidopsis.

Highlights

  • Degreening of leaves is the visible part of the senescence program

  • We summarize the current knowledge on the role of WRKY factors with a special focus on WRKY53

  • Chlorophyll is broken down and the photosynthetic apparatus is dismantled leading to light green and yellowish leaves. When these signs become apparent, the senescence program got into gear long before and molecular changes were already realized on several levels

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Summary

Introduction

Degreening of leaves is the visible part of the senescence program. Chlorophyll is broken down and the photosynthetic apparatus is dismantled leading to light green and yellowish leaves. Genes related to abscisic acid (ABA) and jasmonic acid (JA) production and signaling are induced indicating that ROS, ABA and JA are important early signals in leaf senescence. This is in agreement with a relatively early increase in JA [3] and the even earlier increase of intracellular hydrogen peroxide contents during bolting and flowering of Arabidopsis plants, which coincides exactly with the time point when monocarpic senescence is induced [1]. Lowering hydrogen peroxide levels in Arabidopsis plants delayed the onset of leaf senescence [2] These massive transcriptional changes imply a central role for transcription factors. In the following we portray regulatory mechanisms in Arabidopsis

TpWRKYs
Chromatin Remodeling
Regulation of WRKY53 Expression
Target Genes
Redox Regulation at the WRKY53 Promoter
DNA-Binding Activity Control beyond ROS
Degradation of the WRKY53 Protein
Connecting Early and Late Leaf Development
Conclusions and Future Perspectives
Connecting diagram illustratingthe theWRKY53

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