Small RNA-Based Antiviral Defense in the Phytopathogenic Fungus Colletotrichum higginsianum   
K. GILBERT (1), S. Campo (2), J. Carrington (1) (1) Donald Danforth Plant Science Center, U.S.A.; (2) Centre for Research in Agricultural Genomics, Spain

Colletotrichum higginsianum, a member of a group of plant pathogens that cause disease in many crop species, infects Arabidopsis thus providing the opportunity to study and manipulate both host and pathogen. To characterize the role of RNA silencing in C. higginsianum during vegetative growth and plant-pathogen interactions, knock-out mutants of RNAi machinery genes were created. For identification of small RNA producing loci, mRNAs and small RNAs were sequenced from mycelial tissue of each mutant. Further, immunoprecipitation of AGO1 protein followed by small RNA sequencing was used to specifically identify small RNAs loaded into AGO1. The greatest effect on RNA populations was observed in the dcl1 and ago1 strains related to the de-repression of an uncharacterized dsRNA virus. Viral infections of fungi are primarily asymptomatic. In C. higginsianum no effect was observed on vegetative growth of any mutant on either complex or minimal media. However, dcl1 and ago1 strains produced six- and three-fold fewer conidia, respectively. Since the initial biotrophic phase of infection by C. higginsianum requires an interaction between a spore and the host surface, a decrease in the number of available spores negatively affects fitness with respect to infection initiation. C. higginsianum requires RNA silencing machinery to control virus proliferation to prevent a deficiency in conidation, a crucial step in its lifecycle, both as a free-living organism and as a pathogen.

Abstract Number: P10-336
Session Type: Poster