The core effectome of smut fungi and its functional analysis in Ustilago maydis

Plant pathogenic smut fungi establish a biotrophic interaction with their respective host plants, and this relationship is governed by secretion of fungal effector proteins. Such effector proteins suppress plant immune responses, facilitate nutrition and regulate the progress of the infection process. The release of the Ustilago maydis genome led to uncovering its effector repertoire, clustering of effector genes in the genome and the demonstration that these molecules are crucial determinants for virulence. By now the genomes of the smut fungi U. maydis, U. hordei, U. bromivora, Sporisorium reilianum f. sp. zeae, S. reilianum f. sp. reilianum, S. scitamineum and Melanopsichium pennsylvanicum parasitizing six different plant species are available. We have used comparative genomic studies of the secretomes of these species to provide evolutionary and functional information on the effector repertoires. We are particularly interested in effectors without predicted functional domains that are conserved (core) among all abovementioned species. We present the in silico definition of the core effectome of smut fungi, analysis of the expression pattern of the core effectors in U. maydis and preliminary results on the assessment of virulence of single core effector mutants and core effector family mutants via reverse genetics.