CSLYK6VSWT

Citrus bacterial canker (CBC) results from Xanthomonas citri subsp. citri (Xcc) infection and poses a grave threat to citrus production. Lysin motif receptor-like kinases (LYKs) plays a crucial role in plant-microbe interaction. During microbial infection, LYK recognizes the microbial entry into the host cell and triggers plant defense responses against pathogens. CsLYK6 was identified as a candidate Xcc-inducible factor that is upregulated in the CBC-resistant variety, however, the roles and mechanistic basis of CsLYK6 involved in CBC regulation is poorly defined. Herein, we explored the role of CsLYK6 and its contribution to plant defenses in molecular detail. Overexpression of CsLYK6 resulted in strong CBC resistance in transgenic sweet oranges, whereas silencing of CsLYK6 resulted in susceptibility to CBC. CsLYK6 interacts with and phosphorylates CsCPK13 determined by GST-pull down, Y2H and BiFC and phosphorylated proteome assay. In addition, CsLYK6 was involved in CBC regulation via CsRBOH5 and CsCAT1-mediated ROS burst, by reprogramming the transcription and phosphorylation. Moreover, via Y1H, EMSA, Dual-LUC, as well as transient overexpression, CsDOF5.8 was found to directly binds the CsLYK6 promoter to activate its transcriptional activity. Overall, our results outlined a pathway through which the CsLYK6-CsCPK13 module, regulated by CsDOF5.8, positively affect citrus bacterial canker resistance via reprogramming CsRBOH5 and CsCAT1-mediated ROS burst in citrus. These findings extend current knowledge regarding the functions of LYK family members that govern phytopathogen resistance, underscoring the potential importance of CsLYK6, CsCPK13, CsDOF5.8, CsCAT1 and CsRBOH5 in the breeding of CBC-tolerant citrus plants.