Identifying differences in gene expression between Race 1 and Race 3 strains of Ralstonia solanacearum during bacterial wilt disease development at warm and cool temperatures. J. M. JACOBS (1), F. Meng (1), C. Allen (1)
(1) University of Wisconsin, Department of Plant Pathology, 1630 Linden Dr., Madison, WI 53706
Phytopathology 98:S73

Abstract: The plant pathogenic bacterium Ralstonia solanacearum elicits wilt disease on many hosts, causing significant losses for farmers worldwide. One group in this species complex, Race 3 biovar 2 (R3bv2), persists and causes disease at moderately cool temperatures, in contrast to tropical R. solanacearum strains. Genome sequences of R3bv2 strain UW551 and tropical Race 1 biovar 3 strain GMI1000 suggest about 10% of UW551 ORFs are not present in GMI1000; these may explain R3bv2’s temperate epidemiology. UW551 and GMI1000 behave similarly in vitro at cold (4C), cool (20C) and warm (29C) temperatures, but UW551 is nevertheless much more virulent on tomato plants at 20C than GMI1000. This result suggests that we must study UW551 gene expression in planta to understand how it causes wilt disease at cooler temperatures. These phenotypic observations and the genomic differences between strains will frame a comparative gene expression analysis of GMI1000 and UW551 during infection of tomato plants at 20C and 29C. We therefore designed microarrays representing the GMI1000 and UW551 genomes and developed methods for extracting quality bacterial RNA from infected tomato plants. This powerful four-way comparison of two different strains and temperatures should suggest the molecular mechanisms that govern R3bv2 cold tolerance.