Moreover, although the poor concordance between previously identified virulence factors

(based on murine experimentation) and differentially regulated genes is noted by the authors of Walker et al, it is not possible to comment upon the relevance of this observation, given the absence of virulence data in the rabbit model of infection and the differing scale of experimentation. We found little concordance between metabolic functions upregulated in animal vs. plant pathogens, an observation that may have relevance to the differential retention of saprophyte gene sets among plant pathogens. Similarities, where found, reside in transport, virulence and stress-related selleck chemicals llc functional cohorts (Table 2). Moreover, a striking similarity in higher order gene regulatory activity can be found in instances where positional information is easily retrievable from genome annotation. Thus far, the phenomenon has been reported in U. maydis (Kamper et al., 2006), A. fumigatus (McDonagh et al., 2008) and M. grisea (Collemare et al., SGI-1776 mouse 2008), although few microarray datasets have been appropriately

scrutinized. A significant paradigm shift in eukaryotic genome biology was the discovery that genes involved in functionally related pathways often cluster at proximal genomic locations (Keller & Hohn, 1997). The sequencing of numerous pathogen genomes and advances in bioinformatic and molecular biology has reinforced gene clusters as a common feature of fungal genomes. The term ‘cluster’ has been used

to refer to significant Dehydratase portions of DNA enriched for certain features, such as transposons located in centromeric regions of the C. neoformans genome (Loftus et al., 2005), or lineage-specific genes found in 13 chromosomal islands of the A. fumigatus genome (Fedorova et al., 2008). The term is also used to refer to smaller numbers of genes located adjacently within relatively small loci. Such contiguous genes can collectively direct the biosynthesis of a small molecule, such as a secondary metabolite (Keller et al., 2005), or may simply be genes of related function, such as clusters of genes with putative signal peptides found in U. maydis (Kamper et al., 2006). The size, gene content and products of clusters are diverse; of special interest to the study of pathogenesis is the enrichment of virulence-associated genes within large chromosomal regions or their presence in contiguous clusters. These phenomena pose two challenging questions: what is the impact of the encoded biosynthetic products during pathogenesis and why are some virulence-associated genes clustered? In vivo gene expression profiling of clinically and agriculturally relevant fungal pathogens is proving to be a highly useful tool for determining the evolutionary origin of clusters and their impact on virulence.