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Potential role of small noncoding RNAs in regulating hypovirulence in Rhizoctonia solani anastomosis group 3

Ethel Champaco: University of Maine

<div>Double-stranded RNA (dsRNA) elements are frequently associated with fungi. In <em>Rhizoctonia solani</em> anastomosis group-3 (AG3), the 3.6 kb dsRNA element M2 has been associated with the hypovirulence of Rhs1A1 strain, enabling its use as a biological control agent. Previous studies that examined the role of M2 in downregulating virulence led to a number of hypotheses, but the precise molecular mechanisms are yet to be elucidated. We began to address the hypothesis that M2 might be a possible source of noncoding regulatory RNAs involved in downregulating the expression of virulence-associated genes encoded in the nuclear genome either by post-transcriptional or transcriptional gene silencing mechanisms. We conducted a parallel analysis of RNA-Seq data of the virulent strain (Rhs1AP) and hypovirulent strains (Rhs1A1 and Bs69) using mycelial RNAs from cultures grown on isopore membranes overlaid on potato dextrose agar. Over two dozen noncoding regulatory RNAs <em>(miRNA, siRNA)</em> that could potentially arise from M2 were identified. Possible targets of these regulatory RNAs in the nuclear genome were also identified for reverse co-expression analysis.</div>