Identifying plant resistance pathways in Arabidopsis thaliana

Abstract

The destruction of plants by a pathogen results in millions of dollars lost in crop yield annually. Identifying the plant response pathway to the presence of a pathogen is key to combating plant disease. The gene-for-gene hypothesis suggests that for every pathogen avirulence gene (avr), there is a corresponding specific plant resistance (R) gene that recognizes it and elicits a defense response. One method for discovering resistance pathways is through the use of a suppressor screen in which the deletion or mutation of a negative regulator can reactivate a signaling pathway. Our srfr (suppressor of rps4-RLD) mutants were discovered to provide resistance to the Pseudomonas syringae pv. tomato DC3000 expressing avrRps4 and thus is possibly a regulatory gene. The srfr mutants reactivated resistance to avrRps4 in plants that have a non-functional RPS4 gene. We are studying to see if the srfr gene signaling pathway reactivates avr responses dependent on R genes other than RPS4. We chose the well-studied RPM1 gene, which functions in detecting bacteria expressing avrRpm1. After crossing srfr3 and rpm1-3 mutants and harvesting F1 seeds, we grow these F1 seeds to get the F2 generation population. We isolated genomic DNA from F2 plants and then applied PCR based markers to find homozygous double mutants using 2 genetic markers linked to the srfr3 and rpm1-3 mutation, respectively. The F3 generation plants will be available to test disease symptoms in these double mutants. Based on the results of disease symptoms of the F3 population against bacteria expressing avrRpm1, we will propose whether or not the srfr3 gene is involved in the RPM1 defense signaling pathway. If the F3 generation is susceptible to avrRpm1, then srfr3 is not involved in the RPM1 defense signaling pathway.