Implication of an Aldehyde Dehydrogenase Gene and a Phosphinothricin N-Acetyltransferase Gene in the Diversity of Pseudomonas cichorii Virulence

Abstract

Pseudomonas cichorii harbors the hrp genes. hrp-mutants lose their virulence on eggplant but not on lettuce. A phosphinothricin N-acetyltransferase gene (pat) is located between hrpL and an aldehyde dehydrogenase gene (aldH) in the genome of P. cichorii. Comparison of nucleotide sequences and composition of the genes among pseudomonads suggests a common ancestor of hrp and pat between P. cichorii strains and P. viridiflava strains harboring the single hrp pathogenicity island. In contrast, phylogenetic diversification of aldH corresponded to species diversification amongst pseudomonads. In this study, the involvement of aldH and pat in P. cichorii virulence was analyzed. An aldH-deleted mutant (ΔaldH) and a pat-deleted mutant (Δpat) lost their virulence on eggplant but not on lettuce. P. cichorii expressed both genes in eggplant leaves, independent of HrpL, the transcriptional activator for the hrp. Inoculation into Asteraceae species susceptible to P. cichorii showed that the involvement of hrp, pat and aldH in P. cichorii virulence is independent of each other and has no relationship with the phylogeny of Asteraceae species based on the nucleotide sequences of ndhF and rbcL. It is thus thought that not only the hrp genes but also pat and aldH are implicated in the diversity of P. cichorii virulence on susceptible host plant species.

Coffee bacterial diseases: a plethora of scientific opportunities

“…Similar Pch dependence on hrp genes to cause disease on some hosts but not on others was observed when hrpW (Kajihara et al, 2012) and hopA1 (Hung et al, 2014) were deleted in strain JBC1. In Pch, the aldH and pat genes, coding for an aldehyde dehydrogenase and a phosphinothricin N-acetyltransferase, respectively, are linked to the hrp gene cluster, and their deletions also result in the inability of the bacterium to cause disease on eggplant but not on lettuce (Tanaka et al, 2012). Overall, these observations indicate that Pch uses different mechanisms to cause disease on different hosts.…”