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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


Aspartyl protease mediated cleavage of AtBAG6 triggers autophagy and fungal resistance in plants
Y. LI (1), M. Kabbage (2), M. Dickman (1) (1) Texas A&M University, U.S.A.; (2) University of Wisconsin-Madison, U.S.A.

The Bcl-2-associated-athanogene (BAG) family is an evolutionarily conserved group of co-chaperones that modulate numerous cellular processes. Previously we found that Arabidopsis BAG6 (AtBAG6) is required for basal immunity against the fungal phytopathogen Botrytis cinerea. However, the mechanism(s) by which AtBAG6 controls immunity are obscure. Here, we address this important question by determining the molecular mechanisms responsible for AtBAG6 mediated basal resistance. We show that AtBAG6 is cleaved in vivo in a caspase-1 like dependent manner, and via a combination of pull-downs, mass spectrometry, yeast-two-hybrid and chemical genomics, we demonstrate that AtBAG6 interacts with a C2-GRAM domain protein (AtBAGP1) and an aspartyl protease (AtAPCB1), both of which are required for AtBAG6 processing. Furthermore, fluorescence and transmission electron microscopy established that AtBAG6 cleavage triggers autophagy in the host that coincides with disease resistance. Targeted inactivation of AtBAGP1 or AtAPCB1 results in the blocking of AtBAG6 processing and loss of resistance. Mutation of the cleavage site blocks cleavage, inhibits autophagy and disease resistance is compromised. Taken together, these results couple an aspartyl protease with a molecular co-chaperone to trigger autophagy and plant defense, providing a key link between fungal recognition and the induction of cell death and resistance.