Silencing Genes in Arabidopsis Downy Mildew Using Exogenously Applied Small RNAs

The interaction between Arabidopsis thaliana and diploid biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa) has been a model for investigating plant-pathogen systems. Several R-genes conferring resistance to Hpa and signalling genes playing a role in the immune system have been cloned from Arabidopsis. Similarly, several effectors from Hpa that are recognized by the cloned R-genes have been identified and investigated. Although a vast amount of resources including mutant lines for Arabidopsis exist, lack of genetic manipulation methods for Hpa has hampered studies on pathogenicity related genes. This, in turn, has hindered the discovery of Hpa genes that are involved in spore germination, appressorium, haustorium and conidiophore development. We investigated whether the exogenous application of small RNAs, known as spray-induced gene silencing (SIGS), could silence selected target genes in Hpa. We showed that it is possible to use single or double stranded sRNAs to silence these targeted genes. The latest findings will be presented.