Deciphering New Pathogen Resistance Genes through Comparative Genomics

On Thursday, February 9, 2017, Dr. Christopher Clarke of the United States Department of Agriculture’s Agricultural Research Service shared the stories of several experiments he performed that were aimed at discovering new disease resistance traits in tomato and potato.  By looking at the genes of the plant pathogen Ralstonia solanacearum and finding core effectors that plants could recognize and use to activate their defenses, Dr. Clarke and his collaborators hope to work on finding more durable resistance traits.  Dr. Clarke also worked with the pathogen Psuedomonas syringae pv. tomato (Pto) where they used genome data to study the evolution of the organism.  They found that the majority of Pto strains isolated since the 1970s belong to the T1 lineage (Cai et al., 2011).   

Additionally, they found that the flagellin that was produced by their Pto isolates showed differential response by the plant in reactive oxygen species production. This is a measure commonly used to measure plant defense activation.  Some of the alleles for flagellin production contained single nucleotide polymorphisms (SNPs), which caused altered responses from the plants.  One of their strains had alleles with a high number of SNPs. This caused a reduced response from the host, which allowed for better infection potential of the pathogen.  Dr. Clarke said that his favorite part of doing research is finding something that was unknown before, and the potential to have a positive impact on the agricultural industry.

Cai, R., J. Lewis, S. Yan, H. Liu, C.R. Clarke, F. Campanile, et al. 2011. The Plant Pathogen Pseudomonas syringae pv. tomato Is Genetically Monomorphic and under Strong Selection to Evade Tomato Immunity. PLOS Pathogens 7: e1002130. doi:10.1371/journal.ppat.1002130.

Chart: http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1002130

         Chart is from the article as well