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

Abstract

Background Leaf 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. Results In 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. Conclusion Our 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.

Leaf senescence: progression, regulation, and application

“…Rice ETHYLENE RE-SPONSE FACTOR 101 (OsERF101) promotes the onset and progression of leaf senescence by binding to the promoters of OsNAP and OsMYC2, which activate genes involved in chlorophyll degradation and JA signalingmediated leaf senescence (Lim et al 2020). Wheat TaWRKY42-B promotes leaf senescence mainly by targeting a JA biosynthesis gene, TaLOX3, which consequently contributes to JA accumulation in dark-induced leaf senescence (Zhao et al 2020). Apple (Malus domestica) BT2 protein interacts with MtJAZ protein and MtMYC2, and negatively regulates JA-triggered leaf senescence by modulating the stability of MtMYC2 and MtJAZ2 (An et al 2020).…”

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

“…The wheat copper-binding protein (WCBP1) is tightly related to the regulation of leaf senescence when wheat plants undergo the infection of stripe rust (Li et al, 2015 ). Our data reveal TaWRKY42-B and TaWRKY40-D as positive regulators in phytohormone-related wheat leaf senescence (Zhao et al, 2020a , b ). Moreover, cisZOGT1, a cis -zeatin O -glucosyltransferase, is involved in wheat leaf senescence by regulating CK and N metabolism (Wang et al, 2019 ).…”

“…To identify WRKY 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 <25% leaf area yellowing; and LS, late senescence leaves with >50% leaf area yellowing) in wheat (cv. Chinese Spring) (Zhao et al, 2020b ) and selected a WRKY TF (TraesCS4A02G193600.1) that shows a more significantly increasing expression trend during leaf senescence than its paralogs on chromosomes B and D ( Supplementary Figures 1B,C ). Hence, in this study, we mainly focused on this gene.…”

“…Some studies have revealed the connection between WRKYs and phytohormones in the regulation of leaf senescence. Moreover, some experimental data suggested that there is a feedback loop among leaf senescence, phytohormones, and WRKYs, which makes the regulation of WRKYs in leaf senescence more sophisticate (Miao and Zentgraf, 2007 ; Jiang et al, 2014 ; Guo et al, 2017 ; Kim et al, 2019 ; Zhao et al, 2020b ). This fine-tuning also suggests that the progression of leaf senescence is a highly ordered process.…”

Comparative Transcriptome-Based Mining of Senescence-Related MADS, NAC, and WRKY Transcription Factors in the Rapid-Senescence Line DLS-91 of Brassica rapa

“…Analysis of mutant Arabidopsis lines of WRKY45 has demonstrated that this gene binds to RGA-LIKE1 (RGL1) and promotes age-triggered leaf senescence [ 35 ]. Various other studies have uncovered the roles of WRKY genes as central regulators during leaf senescence in cotton ( GhWRKY17 [ 36 ], GhWRKY27 [ 37 ], GhWRKY42 [ 38 ], and GhWRKY91 [ 39 ]), wheat ( TaWRKY42-B [ 40 ]), Arabidopsis ( AtWRKY55 [ 41 ] and AtWRKY75 [ 42 ]), and Chinese flowering cabbage ( BrWRKY65 [ 43 ]).…”