Comparative Pathogenomics Reveals Horizontally Acquired Novel Virulence Genes in Fungi Infecting Cereal Hosts

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. Comparative analysis of pathogen genomes provides a route to understanding how diverse pathogens have evolved both shared and different virulence strategies to invade cereals. Fusarium crown and root rots are an important disease of wheat and barley in a number of regions world-wide and in Australia these diseases are primarily caused by Fusarium pseudograminearum. The F. pseudograminearum genome has been sequenced and a broad comparative genomics analysis indicated that the F. pseudograminearum genome encodes proteins that have strong homology to proteins that are unevenly distributed across other cereal pathogens, some also with significant bacterial sequence matches, but absent in non-cereal infecting fungi. This is suggestive of multiple horizontal gene acquisition events and phylogenetic analysis of selected genes supported the notion of horizontal gene transfer into diverse cereal pathogens. Two potentially horizontally acquired genes were studied functionally via gene knockout and shown to have important roles in the virulence of F. pseudograminearum on cereal hosts. Our results illustrate the importance of horizontal gene transfer in the evolution of cereal pathogens.