Linking sugar sensing to immunity in plants via O-glycosylation

Interaction with microbes can reprogram metabolism and alter nutrient availability in plant cells. How metabolic cues modulate immune responses remains unknown. Here, we show that sugar-sensing O-glycosylation of immune-signaling kinases mediates metabolic regulation of immunity. Under sugar-replete conditions, the MAP kinase kinases (MKK4 and MKK5), key components of pattern-triggered immunity (PTI), are glycosylated by O-GlcNAc and O-fucose in their activation loops and thus cannot be activated by upstream kinases, thereby restricting PTI. Pathogen infection or sugar starvation reduces O-glycosylation of MKK4/5 and enhances immune signaling; these effects are reversed by GDP-fucose treatme