Pseudomonas syringae pv. tomato DC3000 CmaL (PSPTO4723), a DUF1330 Family Member, Is Needed To Produce l - allo -Isoleucine, a Precursor for the Phytotoxin Coronatine

Abstract

b Pseudomonas syringae pv. tomato DC3000 produces the phytotoxin coronatine, a major determinant of the leaf chlorosis associated with DC3000 pathogenesis. The DC3000 PSPTO4723 (cmaL) gene is located in a genomic region encoding type III effectors; however, it promotes chlorosis in the model plant Nicotiana benthamiana in a manner independent of type III secretion. Coronatine is produced by the ligation of two moieties, coronafacic acid (CFA) and coronamic acid (CMA), which are produced by biosynthetic pathways encoded in separate operons. Cross-feeding experiments, performed in N. benthamiana with cfa, cma, and cmaL mutants, implicate CmaL in CMA production. Furthermore, analysis of bacterial supernatants under coronatine-inducing conditions revealed that mutants lacking either the cma operon or cmaL accumulate CFA rather than coronatine, supporting a role for CmaL in the regulation or biosynthesis of CMA. CmaL does not appear to regulate CMA production, since the expression of proteins with known roles in CMA production is unaltered in cmaL mutants. Rather, CmaL is needed for the first step in CMA synthesis, as evidenced by the fact that wild-type levels of coronatine production are restored to a ⌬cmaL mutant when it is supplemented with 50 g/ml L-allo-isoleucine, the starting unit for CMA production. cmaL is found in all other sequenced P. syringae strains with coronatine biosynthesis genes. This characterization of CmaL identifies a critical missing factor in coronatine production and provides a foundation for further investigation of a member of the widespread DUF1330 protein family.

Ca 2+ -Induced Two-Component System CvsSR Regulates the Type III Secretion System and the Extracytoplasmic Function Sigma Factor AlgU in Pseudomonas syringae pv. tomato DC3000

“…Decreased spread of chlorotic symptoms by P. syringae pv. tomato DC3000 commonly occurs as a result of changes in T3Es or coronatine production (71)(72)(73). While we have not investigated whether CvsSR regulates coronatine production in P. syringae pv.…”

Defining essential processes in plant pathogenesis with Pseudomonas syringae pv. tomato DC3000 disarmed polymutants and a subset of key type III effectors

“…T3SS – mutants of Pst DC3000 and D28E have a significant basal growth ability in N. benthamiana and can even produce COR‐dependent chlorosis (Chakravarthy et al ., ; Worley et al ., ). The ability of DC3000 mutants and phylogenetic subgroup 2c strains of P. syringae to grow in a T3SS‐independent manner in N. benthamiana has been observed previously (Clarke et al ., ; Hann and Rathjen, ).…”

“…As noted in Table 1 and Fig. 1, a gene encoding a previously unknown step in CMA production was lost with deletion of T3E gene cluster IX in the construction of D28E (Munkvold et al, 2009;Worley et al, 2013). The reduced chlorosis linked to cluster IX deletion led to the discovery of cmaL, which directs the production of the L-alloisoleucine precursor of CMA .…”

The Pseudomonas syringae Type III Effector HopG1 Induces Actin Remodeling to Promote Symptom Development and Susceptibility during Infection

“…cluster IX) of virulence factors and T3E genes that have recently been characterized as being associated with the induction of chlorosis (Fig. 4A) (Worley et al, 2013). To determine whether HopG1 function is associated with the induction of chlorosis during Pst DC3000 infection of Arabidopsis, 10-d-old seedlings were dip-inoculated with Pst DC3000, the original effector polymutant lacking HopG1 (i.e.…”