A novel LRR receptor-like kinase BRAK reciprocally phosphorylates PSKR1 to enhance growth and defense in tomato

Plants face constant threats from pathogens, leading to growth retardation and crop failure. Cell-surface leucine-rich repeat receptor-like kinases (LRR-RLKs) are crucial for plant growth and defense, but their specific functions, especially to necrotrophic fungal pathogens, are largely unknown. Here, we identified an LRR-RLK (Solyc06g069650) in tomato (Solanum lycopersicum) induced by the economically important necrotrophic pathogen Botrytis cinerea. Knocking out this LRR-RLK reduced plant growth and increased sensitivity to B. cinerea, while its overexpression led to enhanced growth, yield, and resistance. We named this LRR-RLK as BRAK (B. cinerea resistance-associated kinase). Yeast two-hybrid screen revealed BRAK interacted with phytosulfokine (PSK) receptor PSKR1. PSK-induced growth and defense responses were impaired in pskr1, brak single and double mutants, as well as in PSKR1-overexpressing plants with silenced BRAK. Moreover, BRAK and PSKR1 phosphorylated each other, promoting their interaction as detected by microscale thermophoresis. This reciprocal phosphorylation was crucial for growth and resistance. In summary, we identified BRAK as a novel regulator of seedling growth, fruit yield and defense, offering new possibilities for developing fungal disease-tolerant plants without compromising yield. Plant growth and defense against pathogens are tightly regulated by receptor-like kinases (RLKs) located at the cell surface. This study identifies a novel leucine-rich repeat (LRR)-RLK in tomato, BRAK (Botrytiscinerea resistance-associated kinase), which simultaneously promotes plant growth and boosts resistance to the necrotrophic pathogen B. cinerea.BRAK promotes tomato seedling growth, fruit yield and defense against .BRAK interacts with the phytosulfokine (PSK) receptor PSKR1, and BRAK-regulated growth and defense is related to the PSK signaling pathway.Reciprocal phosphorylation between BRAK and PSKR1 is critical for growth and defense. The trade-off between pathogen resistance and growth is bypassed by the interaction between two membrane kinases.