Comparative gene expression profile analysis of temperate and tropical strains of Ralstonia solanacearum.
J. M. JACOBS (1), F. Meng (1), L. Babujee (1), C. Allen (1) (1) University of Wisconsin-Madison, Madison, WI, USA.
Phytopathology 99:S57

Abstract: Bacterial wilt is a major source of crop losses on diverse hosts, primarily in warm-temperate and tropical zones. However the Race 3 biovar 2(R3bv2) subgroup of the pathogen, Ralstonia solanacearum, attacks plants in temperate zones and the highland tropics. We found that a phylotype II R3bv2 strain, UW551, and a phylotype I tropical strain, GMI1000, grew equally well in culture at tropical and temperate temperatures and caused comparable wilting on tomato at tropical temperatures. In contrast, at a temperate 20C, the R3bv2 strain was a much more aggressive pathogen. Although a large core of ORFs are conserved across R. solanacearum strains, about 10% of the R3bv2 ORFs are not present in the GMI1000 genome; the functions of these genes may explain the biological differences between the strains. We designed whole-genome microarray chips for UW551 and GMI1000 to test the hypothesis that the strains express different transcriptomes at different temperatures in culture and during pathogenesis. Multiple familiar factors contribute to R. solanacearum virulence, but little is known about the specific functions this pathogen needs to succeed in its understudied habitat, the plant xylem tissue. Characterization of plant-induced and low-temperature-induced genes should identify mechanisms underlying both wilt pathogenesis in general and the specific temperate ecological trait of R3bv2.