Identifying type III secretion system effectors and interacting proteins in plant growth-promoting Pseudomonas syringae GR12-2

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University of New Brunswick


The type III secretion system (T3SS) secretes effector proteins that contribute to the virulence of Pseudomonas syringae pathovars. The plant growth-promoting strain P. syringae GR12-2 possesses a Rhizobiales-type T3SS of unknown function, although previous research showed that it is not required for plant interactions. This research aimed to determine the function of the P. syringae GR12-2 T3SS by identifying secreted effectors. Mass spectrometry identified several alginate biosynthesis proteins and a predicted T3SS chaperone exclusively in the extracellular medium of the wild-type but not T3SS mutant strains. Affinity purification of proteins that interacted with the predicted T3SS chaperone included several that function in cell wall synthesis and remodelling. Confirmation of the candidate effectors’ interaction with or secretion by the T3SS will provide insight into potentially novel functions of the T3SS in P. syringae GR12-2.