Association of secondary metabolite gene clusters with host specialization in the cereal blast fungusPyricularia oryzae

Abstract

AbstractFungal plant pathogens constantly evolve and deploy novel peptide and metabolite effectors to break down plant resistance and adapt to new host plants. The blast fungal pathogenPyricularia oryzaeis a single species subdivided into multiple host-specific lineages. This host specialization is likely due to secreted effectors, including metabolite effectors. Here, we mined 68 genomes ofP. oryzae, belonging to six host-specific lineages, to identify secondary metabolite (SM) biosynthetic gene clusters (BGCs) associated with host specialization. A similarity network analysis grouped a total of 4,501 BGCs into 283 gene cluster families (GCFs), based on the content and architecture of the BGCs. While most of the GCFs were present in all theP. oryzaelineages, two were found specifically in theOryzalineage and one was found in the lineage specific toTriticum, LoliumandEleusinehosts. Further analysis of the phylogenetic relationships between core biosynthetic genes confirmed that a BGC, comprising a reducing polyketide synthase (PKS) gene (MGG_08236) and four putative tailoring genes, was present only in theOryzalineage. The predicted BGC was found expressed specifically during host penetration and colonization. We propose that thisOryzalineage-specific BGC is likely associated with a metabolite effector involved in specialization ofP. oryzaeto rice host. Our findings highlight the importance of further exploring the role of metabolite effectors in specialization of the blast fungus to different cereal hosts.