Comparative genomics of Fusarium pseudograminearum reveals novel horizontally acquired virulence genes against cereals. Journal of Plant Pathology.

Cereals are our most important staple crops and are subject to attack from a diverse range of fungal pathogens and a major goal of molecular plant pathology research is to understand how pathogens infect cereal plants to allow the development of durable plant protection measures. Fusarium crown and root rots are important diseases of wheat and barley in a number of regions world-wide. In Australia, Fusarium crown rot is primarily caused by Fusarium pseudograminearum and we have sequenced its genome. A broad comparative genomic analysis indicated that the genome encodes hundreds of proteins whose homologues are unevenly distributed across other cereal pathogens; some with significant bacterial gene sequence matches, but absent in non-cereal infecting fungi. Two genes, one with clear homologues in only Fusarium verticillioides and Colletotrichum graminicola and another with a single clear match in Stagonopsora nodorum, but not in the closely related Fusarium graminearum were studied functionally via gene knockout and using real time PCR to follow gene expression during infection of both roots and leaf material. Both genes are clearly expressed during infection and virulence assays comparing the mutant and parental strains demonstrated the importance of these for virulence on cereal hosts. Our results illustrate the importance of horizontal gene transfer in the evolution of cereal pathogens.