P-316 - Exploiting fungal small RNA effectors to identify quantitative disease resistance genes

Sclerotinia sclerotiorum is a broad host range fungal pathogen, which is responsible for significant crop losses worldwide. S. sclerotiorum relies on molecules such as effector proteins to cause disease. Evidence is emerging that fungal pathogens also secrete small RNAs (sRNAs) during infection, which promote disease by silencing host immunity genes in a process called cross-kingdom RNA interference. We sought to investigate whether S. sclerotiorum sRNAs silence host genes during infection and to determine the role of the targets in disease resistance. In infected Arabidopsis leaf tissue, we identified S. sclerotiorum sRNAs bound to the Arabidopsis RNA-induced silencing complex (RISC) component ARGONAUTE1 (AGO1). Analysis of multiple RNA sequencing datasets in wild-type and mutant Arabidopsis lines identified host genes likely silenced by fungal sRNA-directed AGO1 cleavage during infection. Many of these targets have known or predicted roles in disease resistance. Ongoing research is focused on evaluating specific sRNA-mRNA interactions and determining the role of predicted host targets in resistance to S. sclerotiorum. These fungal sRNA targets may represent strong candidates for improving quantitative disease resistance to S. sclerotiorum through induced genetic variation.