Cotton GhMKK5-GhMPK13 cascade regulates resistance to verticillium wilt by phosphorylating GhBES1-GhPEL75-mediated molecular module.

Verticillium wilt, caused by Verticillium dahliae, is a soil-borne vascular disease that harms many plants, including cotton. The mitogen-activated protein kinase cascade is a highly conserved signal transduction pathway that transmits various extracellular stimuli to downstream targets during plant defense responses. Although there have been many studies on the key role of the mitogen-activated protein kinase cascade in plant disease resistance, mitogen-activated protein kinase signal transduction in cotton remains to be elucidated. Here, we found that GhMKK5 interacted with GhMPK13 and directly phosphorylated GhMPK13. Silencing the homolog GbMKK5 or GbMPK13 in Gossypium barbadense acc. Hai7124 significantly compromised resistance to V. dahliae, accompanied by reduced mitogen-activated protein kinase phosphorylation levels. Conversely, overexpression of GhMKK5 in Arabidopsis enhanced disease resistance and increased phosphorylation of AtMPK3/6. GhMPK13 can phosphorylate BRI1-EMS-SUPPRESSOR 1 (GhBES1), a core transcription factor in the brassinosteroid signaling pathway, which plays a negative regulatory role in resistance to V. dahliae by regulating the expression of pectate lyase 75 (GhPEL75). The phosphorylation of GhBES1 diminishes its binding ability to the promoter of GhPEL75, leading to reduced pectate lyase activity and enhanced disease resistance in cotton. In addition, another interacting protein of GhMPK13, GhSRC1, could improve the stability of GhMPK13, and silencing its expression decreased resistance to V. dahliae. Taken together, our results propose a mitogen-activated protein kinase pathway of GhMKK5-GhMPK13-GhBES1-GhPEL75 in regulating resistance to verticillium wilt in cotton, providing insights into the molecular mechanisms underlying plant cell wall adaptive alteration in the defense response.