The WRKY70 Transcription Factor: A Node of Convergence for Jasmonate-Mediated and Salicylate-Mediated Signals in Plant Defense[W]

Abstract

Cross talk between salicylic acid (SA)-and jasmonic acid (JA)-dependent defense signaling has been well documented in plants, but how this cross talk is executed and the components involved remain to be elucidated. We demonstrate that the plant-specific transcription factor WRKY70 is a common component in SA-and JA-mediated signal pathways. Expression of WRKY70 is activated by SA and repressed by JA. The early induction of WRKY70 by SA is NPR1-independent, but functional NPR1 is required for full-scale induction. Epistasis analysis suggested that WRKY70 is downstream of NPR1 in an SA-dependent signal pathway. Modulation of WRKY70 transcript levels by constitutive overexpression increases resistance to virulent pathogens and results in constitutive expression of SA-induced pathogenesis-related genes. Conversely, antisense suppression of WRKY70 activates JA-responsive/COI1-dependent genes. The effect of WRKY70 is not caused by subsequent changes in SA or JA levels. We suggest that WRKY70 acts as an activator of SA-induced genes and a repressor of JA-responsive genes, integrating signals from these mutually antagonistic pathways.

The novel elicitor AsES triggers a defense response against Botrytis cinerea in Arabidopsis thaliana

“…7). Similar cross-talk events have been described for the B. cinerea-induced protein kinase mutant bik1, that shows inhibition of PDF1.2 but increased SA-induced defense responses [45] and for the activator of SA and repressor of JA-responsive genes, the transcription factor WRKY70 [46,47]. More work would be required to determine the exact localization of these cross-talks in relation to pathogen invasion to determine their relevance.…”

Biosynthesis and emission of insect-induced methyl salicylate and methyl benzoate from rice

“…Because of the central role of the JA signaling pathway in regulating insect-induced MeSA emission, we hypothesize that the regulatory role of NH1 on MeSA production is through the interaction of the SA signaling pathway with the JA pathway. It will be interesting to determine whether the same components mediating the SAeJA crosstalk involved in plantepathogen interactions, such as WRKY70 [18], are also involved in regulating the SAeJA crosstalk in planteinsect interactions.…”

“…The SA pathway is another central defense pathway in plants. In addition to mediating systemic acquired resistance (SAR), the SA signaling pathway interacts with the JA pathway through a crosstalk to regulate plant defense responses [18]. Little is known on whether the SA pathway has a role in the regulation of MeSA production.…”

NPR1: the spider in the web of induced resistance signaling pathways

“…For instance, the Arabidopsis transcription factor WRKY70 acts as both an activator of SA-responsive genes and a repressor of JAinducible genes, thereby integrating signals from these antagonistic pathways [49 ]. In addition, the transcription factor ETHYLENE RESPONSE FACTOR1 (ERF1) integrates signals from the JA and ET pathways in activating defense-related genes that are responsive to both JA and ET [50 ].…”