Genome sequencing reveals the evolution and pathogenic mechanisms of the wheat sharp eyespot pathogen Rhizoctonia cerealis

Abstract

The necrotrophic fungus Rhizoctonia cerealis is the causal agent of devastating diseases of cereal crops including wheat (Triticum aestivum). We present a high-quality genome assembly of R. cerealis Rc207, a virulent strain causing wheat sharp eyespot. The assembly (56.36 Mb) is composed of 17.87% repeat sequences and 14,433 predicted protein-encoding genes. The Rc207 genome encodes a large and diverse set of genes involved in pathogenicity, especially rich in those encoding secreted proteins, carbohydrate-active enzymes (CAZymes), peptidases, nucleases, cytochrome P450, and secondary metabolism-associated enzymes. Most secretory protein-encoding genes, including CAZymes, peroxygenases, dehydrogenases, and cytochrome P450, were up-regulated during fungal infection of wheat. We identified 831 candidate secretory effectors and validated the functions of 10 up-regulated candidate effector proteins. Of them, nine were confirmed as necrotrophic pathogen’s effectors promoting fungal infection. Abundant potential mobile or plastic genomic regions rich in repeat sequences suggest their roles in fungal adaption and virulence-associated genomic evolution. This study provides valuable resources for further comparative and functional genomics on important fungal pathogens, and provides essential tools for development of effective disease control strategies.

Keywords

• Effector
• Evolution
• Pathogenesis
• Rhizoctonia cerealis
• Secretory proteins
• Sharp eyespot