2011 Annual Report
Real time RNA expression studies (qRT-PCR) of R. solanacearum strains in contact with plant roots demonstrated that twitching motility is down-regulated at 18°C when compared with expression at 30°C in strains that are not pathogenic at low temperature, while it is not in strains that are pathogenic at the same temperature. This result suggests that twitching motility is involved directly or indirectly with efficient colonization of the plant host rhizosphere and/or subsequent invasion of roots by the pathogen. Bioinformatics analysis of the set of proteins differentially expressed in our proteomics study revealed a high percentage of hypothetical or non-annotated proteins which could represent novel functions involved in virulence at low temperatures. The analysis also identified proteins with functions associated with oxidative-stress responses and known virulence factors. Preliminary RNA expression experiments for 6 protein candidates seem to confirm a correlation between virulence and expression at low temperature. Currently, qRT-PCR tests are being repeated to confirm our preliminary results, and deletion mutants of two candidate genes are in progress to test their involvement in virulence at low temperature.
Because of its ability to survive and kill solanaceous crops such as potato under cool climate conditions, R3B2 is designated as a “Select Agent” under the Agricultural Bioterrorism Protection Act of 2002. In this work, bacterial wilt strains currently present in the United States that have the potential to survive and infect tomato and potato plants at low temperatures have been identified. It is important to determine the potential environmental fate and movement of these populations within the United States and to identify their virulence determinants at low temperature. If genes involved in establishment under specific temperate conditions are identified for R3B2 and other races of Ralstonia, new methods of control can be developed to safeguard U.S. tomato and potato production.
Research activities under this agreement were monitored by phone calls, e-mails, and reports.