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Free keywords:
Arabidopsis/immunology/*metabolism/*microbiology
Bacterial Proteins/genetics/*metabolism
Evolution, Molecular
Gene Expression Regulation, Enzymologic
Gene Expression Regulation, Plant
Peptide Hydrolases/*metabolism
Phylogeny
Plant Diseases/immunology/*microbiology
Plants, Genetically Modified
Pseudomonas aeruginosa/enzymology/metabolism
Serine Endopeptidases/genetics/*metabolism
Abstract:
Plant innate immunity restricts growth of bacterial pathogens that threaten global food security. However, the mechanisms by which plant immunity suppresses bacterial growth remain enigmatic. Here we show that Arabidopsis thaliana secreted aspartic protease 1 and 2 (SAP1 and SAP2) cleave the evolutionarily conserved bacterial protein MucD to redundantly inhibit the growth of the bacterial pathogen Pseudomonas syringae. Antibacterial activity of SAP1 requires its protease activity in planta and in vitro. Plants overexpressing SAP1 exhibit enhanced MucD cleavage and resistance but incur no penalties in growth and reproduction, while sap1 sap2 double mutant plants exhibit compromised MucD cleavage and resistance against P. syringae. P. syringae lacking mucD shows compromised growth in planta and in vitro. Notably, growth of ΔmucD complemented with the non-cleavable MucD(F106Y) is not affected by SAP activity in planta and in vitro. Our findings identify the genetic factors and biochemical process underlying an antibacterial mechanism in plants.
