The Single-Stranded DNA-Binding Protein WHIRLY1 Represses WRKY53 Expression and Delays Leaf Senescence in a Developmental Stage-Dependent Manner in Arabidopsis

Abstract

Leaf senescence in plants involves both positive and negative transcriptional regulation. In this work, we show evidence for the single-stranded DNA-binding protein WHIRLY1 (WHY1) that functions as an upstream suppressor of WRKY53 in a developmental stage-dependent manner during leaf senescence in Arabidopsis (Arabidopsis thaliana). The why1 mutant displayed an early-senescence phenotype. In this background, the expression levels of both WRKY53 and the senescenceassociated protease gene SAG12 increased. WHY1 bound to the sequence region that contains an elicitor response element motif-like sequence, GNNNAAATT, plus an AT-rich telomeric repeat-like sequence in the WRKY53 promoter in in vivo and in vitro mutagenesis assays as well as in a chromatin immunoprecipitation assay. This binding to the promoter of WRKY53 was regulated in a developmental stage-dependent manner, as verified by chromatin immunoprecipitation-polymerase chain reaction assay. This direct interaction was further determined by a transient expression assay in which WHY1 repressed b-GLUCURONIDASE gene expression driven by the WRKY53 promoter. Genetic analysis of double mutant transgenic plants revealed that WHY1 overexpression in the wrky53 mutant (oeWHY1wrky53) had no effect on the stay-green phenotype of the wrky53 mutant, while a WHY1 knockout mutant in the wrky53 mutant background (why1wrky53) generated subtle change in the leaf yellow/green phenotype. These results suggest that WHY1 was an upstream regulator of WRKY53 during leaf senescence.

Living to Die and Dying to Live: The Survival Strategy behind Leaf Senescence

“…WRKY53 expression is induced by treatment with hydrogen peroxide, which correlates with the observed increased expression of WRKY53 at the time of bolting, during which an increase in endogenous hydrogen peroxide levels has been reported (Miao et al, 2004). Furthermore, WHIRLY1 (WHY1), a protein implicated in plant defense, acts as a negative regulator of WRKY53 expression (Miao et al, 2013). Interestingly, WHY1 was recently proposed to be a redox sensor that moves from the chloroplasts to the nucleus (Foyer et al, 2014).…”

A Genome-Wide Chronological Study of Gene Expression and Two Histone Modifications, H3K4me3 and H3K9ac, during Developmental Leaf Senescence

“…WRKY53 is one example of the many genes that are marked before significant up-regulation of mRNA levels. WRKY53 expression is down-regulated by Whirly1 (Miao et al, 2013), which may explain the coincidence of low transcript levels and high levels of H3K4me3 marks. Examples of posttranscriptional regulation mediated by small RNAs have been identified during leaf senescence (Kim et al, 2009a(Kim et al, , 2009bLi et al, 2013b;Thatcher et al, 2015) and may also explain some of the inconsistencies between H3K4me3 marks and gene expression.…”

POWERDRESS interacts with HISTONE DEACETYLASE 9 to promote aging in Arabidopsis

“…WRKY53 is known to act either as a transcriptional activator or transcriptional repressor in leaf senescence (Miao et al, 2004; Miao and Zentgraf, 2007; Miao et al, 2013). Supporting the relevance of HDA9-WRKY53 interaction, we found that HDA9 binding peaks are significantly enriched for WRKY binding motifs (Figure 3G).…”