A HECT E3 ubiquitin ligase negatively regulates Arabidopsis leaf senescence through degradation of the transcription factor WRKY53

Abstract

SUMMARYWRKY transcription factors play a central role in controlling leaf senescence in Arabidopsis. One important member, WRKY53, is tightly regulated by various mechanisms, and is a convergence node between senescence and pathogen responses. Using WRKY53 in a yeast two-hybrid screen, we isolated the HECT domain E3 ubiquitin ligase UPL5. In contrast to mammals, Arabidopsis contains only seven HECT E3 ubiquitin ligases, whose targets and functions are largely unknown. In yeast cells, UPL5 interacts with WRKY53 via its leucine zipper domain, and this interaction was confirmed in the cytoplasm of plant cells by a bimolecular fluorescence complementation assay. UPL5 was able to use the WRKY53 protein as a substrate for polyubiquitination in an in vitro system, and induction of UPL5 expression by an ethanol-inducible system in upl5 plants led to degradation of the WRKY53 protein. Expression of both genes is regulated antagonistically in response to hydrogen peroxide, jasmonic acid and plant development. Two T-DNA insertion lines (upl5-1 and upl5-2) showed the same senescence phenotype as WRKY53 over-expressers. Over-expression of WRKY53 in the upl5 background enhanced the accelerated senescence phenotype of WRKY53 over-expressers. Therefore, we conclude that UPL5 regulates leaf senescence in Arabidopsis through degradation of WRKY53 and ensures that senescence is executed in the correct time frame.

Endocytic regulation of alkali metal transport proteins in mammals, yeast and plants

“…The ubiquitin ligase activity has only been confirmed for UPL5 Zentgraf 2010, Takahashi, et al 2009). At least one function of this enzyme is related to the regulation of the WRKY53 transcription factor, which controls leaf senescence (Miao and Zentgraf 2010). Accordingly, in this study, they demonstrate in vitro ubiquitylation and physical interaction between UPL5 and WRKY53 and genetic data consistent with UPL5 acting as a negative regulator of WRKY53.…”

A systems biology perspective on the role of WRKY transcription factors in drought responses in plants

“…There are many other examples of wRKY-MAP kinase interactions (Chi et al 2013). Other interacting partners of wRKY proteins include 14-3-3 proteins (Chang et al 2009), chromatin remodeling proteins such as Arabidopsis histone deacetylase 19 (Kim et al 2010), vQ proteins ), CC-NBR-LRR-type R proteins (Shen et al 2007), e3 ubiquitin ligases (Miao and Zentgraf 2010) and the chloroplast ⁄ plastid-localized ABA receptor, ABAR (Shang et al 2010). These interacting partners of wRKY TFs are providing increasing information as to the roles and mechanisms involved in wRKY TF action at the systems level.…”

A Regulatory Cascade Involving Class II ETHYLENE RESPONSE FACTOR Transcriptional Repressors Operates in the Progression of Leaf Senescence

“…Prior studies have described the role of several components of the ubiquitin-proteasome system (Woo et al, 2001;Gepstein, 2004;Lin and Wu, 2004;BuchananWollaston et al, 2005;van der Graaff et al, 2006;Peng et al, 2007;Raab et al, 2009;Miao and Zentgraf, 2010;Breeze et al, 2011). In particular, WRKY53 is degraded by a homologous to the E6-AP carboxyl terminus domain ubiquitin ligase (Miao and Zentgraf, 2010).…”