Post-translational regulation of WRKY transcription factors in plant immunity

Laboratory of Defense in Plant-Pathogen Interactions, Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan.
Current opinion in plant biology (Impact Factor: 7.85). 03/2012; 15(4):431-7. DOI: 10.1016/j.pbi.2012.02.003
Source: PubMed


Plants have evolved immune system to protect themselves against invading pathogens. Recent research has illustrated that signaling networks, after perception of diverse pathogen-derived signals, facilitate transcriptional reprogramming through mitogen-activated protein kinase (MAPK) cascades. WRKY proteins, which comprise a large family of plant transcription factors, are key players in plant immune responses. WRKY transcription factors participate in the control of defense-related genes either as positive or as negative regulators, and essentially are regulated at the transcriptional level. Emerging evidence emphasizes that group I WRKY transcription factors, which contain a conserved motif in the N-terminal region, are also activated by MAPK-dependent phosphorylation, underlining their importance in plant immunity.

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    • "Autoregulation and cross regulation are common features of WRKY action (Ishihama and Yoshioka, 2012). Thus, we examined the transcript levels of OsWRKY70, OsWRKY24, OsWRKY30, OsWRKY45, OsWRKY13, WRKY35, and OsWRKY33, all of which have been reported to be involved in defense responses in rice (Qiu et al., 2007; Shimono et al., 2007; Koo et al., 2009; Li, 2012; Shen et al., 2012), in ir-wrky, oe-WRKY, and wild-type plants after SSB infestation. "
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    ABSTRACT: The mechanisms by which herbivore-attacked plants activate their defenses are well studied. By contrast, little is known about the regulatory mechanisms that allow them to control their defensive investment and avoid a defensive overshoot. We characterized a rice (Oryza sativa) WRKY gene, OsWRKY53, whose expression is rapidly induced upon wounding and induced in a delayed fashion upon attack by the striped stem borer (SSB) Chilo suppressalis. The transcript levels of OsWRKY53 are independent of endogenous jasmonic acid (JA), but positively regulated by the mitogen-activated protein kinases (MPKs), OsMPK3/OsMPK6. OsWRKY53 physically interacts with OsMPK3/OsMPK6 and suppresses their activity in vitro. By consequence, it modulates the expression of defensive, MPK-regulated WRKYs and thereby reduces JA, jasmonoyl-isoleucine (JA-Ile) and ethylene induction. This phytohormonal reconfiguration is associated with a reduction in trypsin protease inhibitor activity and improved SBB performance. OsWRKY53 is also shown to be a negative regulator of plant growth. Taken together, these results show that OsWRKY53 functions as a negative feedback modulator of MPK3/MPK6 and thereby acts as an early suppressor of induced defenses. OsWRKY53 therefore enables rice plants to control the magnitude of their defensive investment during early signaling.
    Full-text · Article · Oct 2015 · Plant physiology
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    • "Thus, these findings indicate that WRKY33 positively regulates ATL31 expression during plant defense responses. Since the activity of WRKY33 is regulated via phosphorylation by MAP kinases during pathogen signaling (Buscaill and Rivas 2014; Ishihama and Yoshioka 2012; Meng and Zhang 2013; Zhang et al. 2002), it suggests that upstream of the transcriptional regulation of ATL31 by WRKY33 may be regulated by MAP kinase signaling components after recognition of PAMPs and Pst. DC3000. "
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    ABSTRACT: ATL31, an Arabidopsis RING-type ubiquitin ligase, plays a critical role in plant carbon/nitrogen (C/N)-nutrient responses during post-germinative growth and in defense responses to pathogen attack. ATL31 expression under these stress conditions suggested the presence of transcriptional regulators mediated by these stress signals. We recently reported that the expression pattern of WRKY33, a transcription factor involved in plant defense responses, is highly correlated with that of ATL31. In this study, we investigated the detailed relationship between the ATL31 gene and WRKY33. Using transient reporter analysis, we found that WRKY33 could significantly activate ATL31 transcription in plant cells. Transcript analysis of stable transgenic Arabidopsis plants overexpressing WRKY33 confirmed that the expression of ATL31 in response to the PAMPs flg22 and chitin was enhanced compared with wild-type plants, while expression was repressed in wrky33 mutants. Further detailed transient reporter analysis revealed that transactivation by WRKY33 is required and mediated through a specific W-box cis-acting element in the promoter region of the ATL31 gene. In contrast, WRKY33 did not regulate ATL31 expression during the C/N response. Taken together, these results demonstrate that WRKY33 acts as a transcription factor of ATL31 and positively regulates its expression during activation of plant defense responses.
    Full-text · Article · Jan 2015 · Plant Biotechnology
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    • "Out of the four subfamilies of AP2/EREBP (i.e., AP2, RAV (related to ABI3/VP1), dehydration-responsive element-binding protein (DREB), and ERF) [45], [46], only the two largest ones, the DREB and ERF subfamilies, were deregulated in the lif2-1 mutant. The plant-specific WRKY transcription factors are key regulators of stress and plant immune responses [47], whereas the NAC TFs are involved in both development and the abiotic and/or biotic stress responses. Two stress-responsive NACs (SNACs) that were recently described [48], [49] were deregulated in the lif2-1 transcriptome. "
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    ABSTRACT: Eukaryotes have evolved complex defense pathways to combat invading pathogens. Here, we investigated the role of the Arabidopsis thaliana heterogeneous nuclear ribonucleoprotein (hnRNP-Q) LIF2 in the plant innate immune response. We show that LIF2 loss-of-function in A. thaliana leads to changes in the basal expression of the salicylic acid (SA)- and jasmonic acid (JA)- dependent defense marker genes PR1 and PDF1.2, respectively. Whereas the expression of genes involved in SA and JA biosynthesis and signaling was also affected in the lif2-1 mutant, no change in SA and JA hormonal contents was detected. In addition, the composition of glucosinolates, a class of defense-related secondary metabolites, was altered in the lif2-1 mutant in the absence of pathogen challenge. The lif2-1 mutant exhibited reduced susceptibility to the hemi-biotrophic pathogen Pseudomonas syringae and the necrotrophic ascomycete Botrytis cinerea. Furthermore, the lif2-1 sid2-2 double mutant was less susceptible than the wild type to P. syringae infection, suggesting that the lif2 response to pathogens was independent of SA accumulation. Together, our data suggest that lif2-1 exhibits a basal primed defense state, resulting from complex deregulation of gene expression, which leads to increased resistance to pathogens with various infection strategies. Therefore, LIF2 may function as a suppressor of cell-autonomous immunity. Similar to its human homolog, NSAP1/SYNCRIP, a trans-acting factor involved in both cellular processes and the viral life cycle, LIF2 may regulate the conflicting aspects of development and defense programs, suggesting that a conserved evolutionary trade-off between growth and defense pathways exists in eukaryotes.
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