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
Summary
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
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