Putative Bifunctional Chorismate Mutase/Prephenate Dehydratase Contributes to the Virulence ofAcidovorax citrulli

초록

Acidovorax citrulli(Ac) is a plant pathogenic bacterium that causes bacterial fruit blotch (BFB) in cucurbit crops. Despite its importance in the cucurbit industry, resistant cultivars/lines against BFB have not yet been identified. Therefore, there is a need to characterize the virulence factors/mechanisms inActo control the disease. Chorismate mutase, a key enzyme in the shikimate pathway, produces aromatic amino acids. Here, we report the functions of putative bifunctionalchorismatemutase/prephenate dehydratase inAc(CmpAc) determined by proteomic analysis and phenotypic assays.Acstrain lacking CmpAc,Ac Delta cmpAc(EV), were significantly less virulent on watermelon in the germinated-seed inoculation and leaf infiltration assays. Sequence analysis revealed that CmpAc possesses two distinct domains: chorismate mutase and prephenate dehydratase, indicating that CmpAc is a bifunctional protein. Auxotrophic assays demonstrated that CmpAc is required for the biosynthesis of phenylalanine, but not tyrosine. The comparative proteomic analysis revealed that CmpAc is mostly involved in cell wall/membrane/envelop biogenesis. Furthermore,Ac Delta cmpAc(EV) showed reduced twitching halo production and enhanced biofilm formation. In addition,Ac Delta cmpAc(EV) was less tolerant to osmotic stress but more tolerant to antibiotics (polymyxin B). Thus, our study provides new insights into the functions of a putative bifunctional protein related to virulence inAc.

키워드