CYSTEINE-RICH RECEPTOR-LIKE KINASE5 (CRK5) and CRK22 regulate the response to Verticillium dahliae toxins

Cysteine-rich receptor-like kinases (CRKs) play critical roles in responses to biotic and abiotic stresses. However, the molecular mechanisms of CRKs in plant defense responses remain unknown. Here, we demonstrated that two CRKs, CRK5 and CRK22, are involved in regulating defense responses to Verticillium dahliae toxins (Vd-toxins) in Arabidopsis (Arabidopsis thaliana). Biochemical and genetic analyses showed that CRK5 and CRK22 may act upstream of MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6 to regulate the salicylic acid (SA)-signaling pathway in response to Vd-toxins. In addition, MPK3 and MPK6 interact with the transcription factor WRKY70 to modulate defense responses to Vd-toxins. WRKY70 directly binds the promoter domains of the SA-signaling-related transcription factor genes TGACG SEQUENCE-SPECIFIC BINDING PROTEIN (TGA2) and TGA6 to regulate their expression in response to Vd-toxins. Thus, our study reveals a mechanism by which CRK5 and CRK22 regulate SA signaling through the MPK3/6-WRKY70-TGA2/6 pathway in response to Vd-toxins. Cysteine-rich receptor-like kinases play critical roles in plant defense responses.