P-085 - Utilizing a loss of non-host resistance Arabidopsis mutant as a tool to find susceptibility factors

EMS mutagenesis is a powerful tool for uncovering genetic information, forming the basis for newer genome editing techniques like CRISPR/Cas. Arabidopsis thaliana is an ideal model for EMS screens due to its fast life cycle, small genome, and minimal space requirements. However, it is primarily used for plant-microbe studies with adapted pathogens. The biotrophic fungus Phakopsora pachyrhizi (Pp), the causal agent of Asian soybean rust (SBR), is a major threat to global soybean production and is not adapted to Arabidopsis. Common approaches to control SBR include single-resistance gene breeding and the application of fungicides. Over time, SBR managed to overcome those single resistance genes, which only leaves the application of fungicides. To address this dilemma, we developed an Arabidopsis mutant susceptible to Pp and used it in an EMS screen for loss of susceptibility factors. To achieve this, a sextuple Arabidopsis mutant was created with mutations in genes central to its immune system, PEN1, PEN2, SYP122, EDS1, NDR1, and FMO1 as well as a NahG transgene, which encodes a salicylic acid hydroxylase that inactivates this signaling molecule. This line was used in an EMS screen, which resulted in several mutants that have regained resistance against Pp. These gene mutations are predicted to be of general importance for Pp susceptibility, and the hope is that we can gain insight useful for obtaining rust resistance in soybean.