The Pseudomonas syringae Hrp pathogenicity island has a tripartite mosaic structure composed of a cluster of type III secretion genes bounded by exchangeable effector and conserved effector loci that contribute to parasitic fitness and pathogenicity in plants

• DOI: 10.1073/pnas.97.9.4856
• Publication Date: 2002-07-26T14:38:21Z
• Authors: James R. Alfano; Amy O. Charkowski; Wen-Ling Deng; Jorge L. Badel; Tanja Petnicki-Oc...; Karin van Dijk; Alan Collmer
• Keywords: Pseudomonas syringae; Pathogenicity island; ORFS; Gene cluster; Conserved sequence

The plant pathogenic bacterium Pseudomonas syringae is divided into pathovars differing in host specificity, with P. pv. ( Psy ) and tomato Pto representing particularly divergent pathovars. hrp / hrc genes encode a type III protein secretion system that appears to translocate Avr Hop effector proteins cells. DNA sequence analysis of the regions 61, B728a, DC3000 has revealed Hrp pathogenicity island (Pai) tripartite mosaic structure. gene cluster conserved all three strains flanked by unique exchangeable locus (EEL) (CEL). EELs begin 3 nt downstream stop codon hrpK end, after 2.5–7.3 kb dissimilar intervening tRNA Leu – queA–tgt sequences are also found aeruginosa but without linkage any Pai sequences. diverse putative effectors, including HopPsyA (HrmA) 61 similar AvrPphE AvrB/AvrC/AvrPphC AvrBsT/AvrRxv/YopJ families B728a. contain mobile genetic element have G + C content significantly lower than rest or genome. CEL carries at least seven ORFs between B728a DC3000. Deletion EEL slightly reduces bacterial growth tomato, whereas deletion large portion strongly abolishes tomato.