D-rhamnose (
D-Rha) residue is a major component of lipopolysaccharides (LPSs) in strains of the phytopathogen
Pseudomonas syringae pathovar
glycinea. To investigate the effects of a deficiency in GDP-
D-rhamnose biosynthetic genes on LPS structure and pathogenicity, we generated three mutants defective in
D-Rha biosynthetic genes, encoding proteins GDP-
D-mannose 4,6-dehydratase (GMD), GDP-4-keto-6-deoxy-
D-mannose reductase (RMD), and a putative α-
D-rhamnosyltransferase (WbpZ) in
P. syringae pv.
glycinea race 4. The Δ
gmd, Δ
rmd, and Δ
wbpZ mutants had a reduced
O-antigen polysaccharide consisting of
D-Rha residues as compared with the wild type (WT). The swarming motility of the Δ
gmd, Δ
rmd, and Δ
wbpZ mutant strains decreased and hydrophobicity and adhesion ability increased as compared with WT. Although the mutants had truncated
O-antigen polysaccharides, and altered surface properties, they showed virulence to soybean, as WT did.
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