TaWRKY13-A Serves as a Mediator of Jasmonic Acid-Related Leaf Senescence by Modulating Jasmonic Acid Biosynthesis.

Hualiang Qiao,Lingling Cheng,Pengcheng Yin,Xuelin Gu,Yongwei Liu,Ke Li,Shuo Zhou,Geng Wang,Chunjiang Zhou

doi:10.3389/fpls.2021.717233

Abstract

Leaf senescence is crucial for crop yield and quality. Transcriptional regulation is a key step for integrating various senescence-related signals into the nucleus. However, few regulators of senescence implicating transcriptional events have been functionally characterized in wheat. Based on our RNA-seq data, we identified a WRKY transcription factor, TaWRKY13-A, that predominately expresses at senescent stages. By using the virus-induced gene silencing (VIGS) method, we manifested impaired transcription of TaWRKY13-A leading to a delayed leaf senescence phenotype in wheat. Moreover, the overexpression (OE) of TaWRKY13-A accelerated the onset of leaf senescence under both natural growth condition and darkness in Brachypodium distachyon and Arabidopsis thaliana. Furthermore, by physiological and molecular investigations, we verified that TaWRKY13-A participates in the regulation of leaf senescence via jasmonic acid (JA) pathway. The expression of JA biosynthetic genes, including AtLOX6, was altered in TaWRKY13-A-overexpressing Arabidopsis. We also demonstrated that TaWRKY13-A can interact with the promoter of AtLOX6 and TaLOX6 by using the electrophoretic mobility shift assay (EMSA) and luciferase reporter system. Consistently, we detected a higher JA level in TaWRKY13-A-overexpressing lines than that in Col-0. Moreover, our data suggested that TaWRKY13-A is partially functional conserved with AtWRKY53 in age-dependent leaf senescence. Collectively, this study manifests TaWRKY13-A as a positive regulator of JA-related leaf senescence, which could be a new clue for molecular breeding in wheat.

Highlights

Leaf senescence is a highly regulated developmental process and triggered by diverse environmental factors (Woo et al, 2019)
To identify WRKY transcription factors (TFs) related to leaf senescence in wheat, we analyzed our RNA-seq data at four developmental stages of flag leaves (i.e., YL, young leaves with half size of mature leaves; ML, mature leaves, fully expanded leaves; ES, early senescence leaves with 50% leaf area yellowing) in wheat
According to the corresponding sequence obtained from the WheatOmics, we confirmed that the candidate gene is TaWRKY13-A that encodes a 24.49-kDa protein of 222 amino acids and with an isoelectric point of 8.33

Summary

Introduction

Leaf senescence is a highly regulated developmental process and triggered by diverse environmental factors (Woo et al, 2019). Phytohormones directly or indirectly regulate the onset and progression of leaf senescence by fine-tuning developmental programs or responses to stress (Jibran et al, 2013; Smith et al, 2017; Zhang et al, 2020). Different hormones participate in the regulation of leaf senescence with a distinct mechanism. Hormones, such as ethylene, abscisic acid, jasmonic acid (JA), salicylic acid (SA), brassinosteroids, and strigolactones, promote the initiation of leaf senescence, whereas cytokinins (CKs), gibberellins, and auxins delay leaf senescence (Arrom and Munne-Bosch, 2012; Khan et al, 2014; Tan et al, 2019; Wojciechowska et al, 2020; Zhang et al, 2021)

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