Genomics of ophiostomatoid fungi: the first two thousand genes

Ophiostomatoid fungi include over one hundred species of saprophytes that colonize the xylem of trees, as well as a few pathogens such as Ophiostoma novo-ulmi, the causal agent of Dutch elm disease. Following the launch of the Canadian Ophiostoma Genome Project in 2001, we have been studying the organization of the nuclear genome of ophiostomatoid fungi and identifying genes that modulate fitness and pathogenicity in O. novo-ulmi. To this end, we are using both structural and functional genomics. Close to 200 nuclear markers were genetically mapped in O. novo-ulmi and some of these markers are now being used for comparative analyses of the nuclear genome among various Ophiostoma species. We constructed complementary DNA expression libraries for various growth phases of O. novo-ulmi (e.g. axenic cultures, fruiting bodies, or cultures that are actively colonizing elm calli). Following largescale sequencing of these libraries and bioinformatic searches in public databases, we have so far identified over 2000 different expressed sequence tags (ESTs). for putative coding sequences in O. novoulmi, a "quantum leap" from the 20 or so genes that had been described previously in this species. This considerable data bank now paves the way for the design and conduct of large-scale experiments that will help us better understand the complex biology of ophiostomatoid fungi.