PSPT04723 Controls the Production of the Coronamic Acid Moiety of Coronatine in Pseudomonas syringae pv. tomato DC3000
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The disease symptoms of Pseudomonas syringae pv. tomato DC3000 are induced by the translocation of effector proteins via the type III secretion system, as well as by the production of various phytotoxins. These virulence factors contribute to the survival of P. syringae within the host apoplast. One phytotoxin in particular, coronatine (COR), is the major determinant of spreading chlorosis in several pathovars of P. syringae. COR is composed of two moieties, coronafacic acid (CFA) and coronamic acid (CMA), linked via an amide bond. CFA is a polyketide and CMA is an ethylcyclopropyl derivative of isoleucine. Phytotoxins and type III effectors may have overlapping functions in virulence, and disentangling these functions is complicated by redundancy and linkage of their genes in horizontally acquired gene clusters. Here, the production of COR, as well as the resulting chlorosis phenotype, was shown to occur independently of the type III effectors, and with minimal bacterial growth within the host apoplast. The small ORF, PSPT04723, located within effector-gene cluster IX of DC3000, was shown to be necessary for the synthesis of COR due to its control over the production of CMA, but not CFA. This chlorosis-promoting factor is a member of the DUF1330 family of hypothetical proteins and appears to play a role in the regulation of the CMA biosynthetic pathway.
dissertation or thesis