FERONIA (FER) is a receptor-like kinase showing versatile functions during plant growth, development, and responses to environmental stimuli. However, its functions during the interaction between fruit and necrotrophic fungal pathogens are still unclear.

Combining reverse genetic approaches, physiological assays, co-immunoprecipitation, protein phosphorylation identification, and site-directed mutagenesis, we reported a tomato FER homolog SlFERL (Solanum lycopersicum FERONIA Like) involved in the immune responses to Botrytis cinerea invasion.

The results indicated that SlFERL extracellular domain recognized and interacted with the secreted virulence protein BcPG1 from B. cinerea, further revealed that SlFERL triggered downstream signaling by phosphorylating SlMAP3K18 at Thr45, Ser49, Ser76, and Ser135. Moreover, we verified that SlMAP2K2 and SlMAP2K4 synergistically contributed to immune response of tomato to B. cinerea, in which SlFERL-SlMAP3K18 module substantially modulated protein level and/or kinase activity of SlMAP2K2/SlMAP2K4.

These findings reveal a new pattern-triggered immune pathway, indicating that SlFERL participates in the immune responses to B. cinerea invasion via recognizing BcPG1 and fine-tuning MAPK signaling.