APS Homepage

Poster: Molecular & Cellular Plant-Microbe Interactions: Biochemistry & Cell Biology


Small RNA processing in Sclerotinia sclerotiorum
S. MARZANO (1), L. Domier (2) (1) South Dakota State University, U.S.A.; (2) USDA/ARS, University of Illinois, Urbana-Champaign, U.S.A.

RNA silencing pathways are under-studied in plant pathogenic fungi. Once elucidated, they can be utilized to improve plant health by more effectively silencing fungal genes from host plants or viral vectors. In this study, we characterized changes in gene expression and small RNA accumulation in Sclerotinia sclerotiorum, a damaging and widely distributed fungal plant pathogen, in response to hypovirus infection. Our results indicated that the fungus produced small RNAs of predominantly 22 nt. The S. sclerotiorum genome was predicted to contain 59 families of microRNA-like (milRNA) genes, which similar to other recently characterized fungal species, were poorly conserved with other eukaryotes. In degradome analyses, 39 of the milRNAs sequences were predicted to mediate cleavage of 47 S. sclerotiorum mRNAs. Consistent with the role of RNA silencing in defense against mobile and infectious genetic elements, most of the small RNA sequences in virus-free S. sclerotiorum were derived from retrotransposons. Similarly, large amounts of predominantly 22 nt sequences were detected from the hypovirus genome, indicating that it also was targeted for degradation by host RNA-mediated antiviral defenses. These findings suggest that virus-induced hypovirulence could result from disruption of RNA silencing and that a robust RNA silencing pathway exists in S. sclerotiorum that can be exploited for RNA-based pathogen resistance strategies.