Characterisation of the polygalacturonase gene of the Dutch elm disease pathogen Ophiostoma novo-ulmi.

Abstract

The fungal pathogens Ophiostoma ulmi (Buisman) Nannf. and O. novo-ulmi Brasier, the causal agents of Dutch elm disease, are responsible for decimation of elms in the Northern Hemisphere during the twentieth and twenty-fi rst centuries. Pectinolytic enzymes, including polygalacturonase, have been implicated as virulence factors in the life history of many fungi. To determine the role of polygalacturonase in Dutch elm disease, we cloned and characterised the polygalacturonase gene from the highly aggressive O. novo-ulmi. This gene was similar to polygalacturonase genes of other fungi, and was present as a single copy in the genome. Genetic disruption of the gene was not lethal to the pathogen but led to a reduction of pectinolytic activity in vitro. It appears, therefore, that polygalacturonase has a limited role in fungal virulence and parasitic fi tness in the life history of O. novo-ulmi.