Salicylic acid (SA) signalling plays an essential role in plant innate immunity. In this study, we identified a component in the SA signaling pathway in potato (Solanum tuberosum), the transcription factor StbZIP61, and characterized its function in defence against Phytophthora infestans. Expression of StbZIP61 was induced upon P. infestans infection and following exposure to the defense signaling hormones SA, ethylene and jasmonic acid. Overexpression of StbZIP61 increased the tolerance of potato plants to P. infestans while RNA interference (RNAi) increased susceptibility. Yeast two-hybrid and pull down experiments revealed that StbZIP61 could interact with an NPR3-like protein (StNPR3L) that inhibited its DNA-binding and transcriptional activation activities. Moreover, StNPR3L interacted with StbZIP61 in an SA-dependent manner. Among candidate genes involved in SA-regulated defense responses, StbZIP61 had a significant impact on expression of StICS1, which encodes a key enzyme for SA biosynthesis. StICS1 transcription was induced upon P. infestans infection and this responsive expression to the pathogen was reduced in StbZIP61 RNAi plants. Accordingly, StICS1 expression was remarkably enhanced in StbZIP61-overexpressing plants. Together, our data demonstrate that StbZIP61 functions in concert with StNPR3L to regulate the temporal activation of SA biosynthesis, which contributes to SA-mediated immunity against P. infestans infection in potato.
Keywords: Phytophthora infestans; SA; Solanum tuberosum; NPR3-like protein; bZIP transcription factor.
© 2018 The Authors The Plant Journal © 2018 John Wiley & Sons Ltd.