Evidence for a positive regulatory role of strawberry (Fragaria×ananassa) Fa WRKY1 and Arabidopsis At WRKY75 proteins in resistance

Abstract

Knowledge of the molecular basis of plant resistance to pathogens in species other than Arabidopsis is limited. The function of Fa WRKY1, the first WRKY gene isolated from strawberry (Fragaria x ananassa), an important agronomical fruit crop, has been investigated here. Fa WRKY1 encodes a IIc WRKY transcription factor and is up-regulated in strawberry following Colletotrichum acutatum infection, treatments with elicitors, and wounding. Its Arabidopsis sequence homologue, At WRKY75, has been described as playing a role in regulating phosphate starvation responses. However, using T-DNA insertion mutants, a role for the At WRKY75 and Fa WRKY1 in the activation of basal and R-mediated resistance in Arabidopsis is demonstrated. At wrky75 mutants are more susceptible to virulent and avirulent isolates of Pseudomonas syringae. Overexpression of Fa WRKY1 in At wrky75 mutant and wild type reverts the enhanced susceptible phenotype of the mutant, and even increases resistance to avirulent strains of P. syringae. The resistance phenotype is uncoupled to PATHOGENESIS-RELATED (PR) gene expression, but it is associated with a strong oxidative burst and glutathione-S-transferase (GST) induction. Taken together, these results indicate that At WRKY75 and Fa WRKY1 act as positive regulators of defence during compatible and incompatible interactions in Arabidopsis and, very likely, Fa WRKY1 is an important element mediating defence responses to C. acutatum in strawberry. Moreover, these results provide evidence that Arabidopsis can be a useful model for functional studies in Rosacea species like strawberry.

Arabidopsis MYC Transcription Factors Are the Target of Hormonal Salicylic Acid/Jasmonic Acid Cross Talk in Response to Pieris brassicae Egg Extract

“…Since woundactivation of VSP2 was strongly diminished in wrky75-25 and maintained after egg extract treatment in 35S: WRKY75, our results are consistent with a positive role of WRKY75 in the control of the JA-regulated genes independently of MYC2. WRKY75 was previously shown to play a role in plant defense against biotrophs and necrotrophs (Encinas- Villarejo et al, 2009;Windram et al, 2012;Chen et al, 2013). Noteworthy, WRKY75 overexpression was accompanied by elevated expression of JA-responsive genes, including PDF1.2, VSP1, and LOX2, and enhanced resistance against the necrotroph Sclerotinia sclerotiorum .…”

An R2R3-MYB Transcription Factor Regulates Eugenol Production in Ripe Strawberry Fruit Receptacles

“…Supplemental Table S5 depicts the primer sequences used for quantitative amplification. Each reaction was performed at least in triplicate, and the corresponding C t values were normalized using the C t value corresponding to an interspacer 26S-18S strawberry RNA gene (Benítez-Burraco et al, 2003;Raab et al, 2006;Encinas-Villarejo et al, 2009;Cumplido-Laso et al, 2012;Molina-Hidalgo et al, 2013). All these values were then used to determine the relative increase or decrease of FaEOBII expression in the samples as compared with those in the control, in accordance with Pedersen (2001).…”

Cotton WRKY1 Mediates the Plant Defense-to-Development Transition during Infection of Cotton byVerticillium dahliaeby ActivatingJASMONATE ZIM-DOMAIN1Expression

“…AtWRKY75 was first identified as a critical modulator of phosphate uptake and phosphate stress responses (Devaiah et al, 2007). Subsequently, AtWRKY75 has been implicated in plant defense to Pseudomonas syringae, and wrky75 mutant plants display increased susceptibility to different P. syringae strains (Encinas-Villarejo et al, 2009). Moreover, the overexpression of AtWRKY75 and its rice ortholog OsWRKY72 causes early flowering in Arabidopsis (Arabidopsis thaliana; Yu et al, 2010).…”