Processing of AtBAG6 triggers autophagy and fungal resistance.

The Bcl-2-associated athanogene (BAG) family is an evolutionarily conserved, multifunctional group of cytoprotective co-chaperones. Using structural bioinformatic approaches we identified 7 homologs of the Arabidopsis BAG family. Evaluating knockouts in Arabidopsis of individual BAG family members, we noted that Arabidopsis BAG6 (AtBAG6) knockout lines exhibited a pronounced enhancement of susceptibility to the necrotrophic fungal pathogen Botrytis cinerea. Moreover, we identified a single predicted caspase-1 site that was cleaved by an aspartyl protease (AtAPCB1). Finally, we showed AtBAG6 forms a complex with AtAPCB1 via coupling to a C2 GRAM domain protein (AtBAGP1). This complex and its activation is necessary for triggering pathogen mediated autophagic cell death and host resistance.