Project description:This experiment exploits the life-cycle of Strongyloides ratti, which is a parasitic nematode of brown rats that exhibits three adult stages within its life-cycle - parasitic females, freeliving females and free-living males. We use a cDNA microarray to examine patterns of (i) gender-biased gene expression by contrasting free-living females against free-living males, and (ii) parasitic-biased expression by contrasting parasitic females against free-living females. Of the 3688 distinct transcripts represented on our array, 20% exhibited male-biased expression 19% exhibit female-biased expression, 11% exhibit parasitic-biased expression and 8% exhibit free-living-biased expression. Among the top responding genes, an orthologue of major sperm protein is upregulated in males, distinct aspartic protease orthologues are upregulated in either parasitic or in free-living females, and orthologues of hsp-17 chaperone are upregulated in parasitic females. Upon a global analysis of gene expression, we find that female-biased expression is associated with genes involved in reproductive processes and larval development, that male-biased expression is associated with genes involved in metabolism, and that free-living biased expression is associated with genes involved in regulation of body fluids and response to external stimulus. The association of gene ontology with parasite-biased expression is less clear. Our results provide an initial gene expression analysis of gender- and parasite-biased expression in S. ratti, may be more generally applicable to other parasitic nematodes, and may help to refine the search for novel drug or vaccine targets against parasitic nematodes.