Comparative Genomics of Gene Expression in the Parasitic and Free-living Nematodes Strongyloides Stercoralis and Caenorhabditis Elegans

While developmental timing of gene expression is used to infer potential genefunction, studies have yet to correlate this information between species. Weanalyzed 10,921 ESTs in 3,311 clusters from first and infective third stagelarva (L1, L3i) of the parasitic nematode Strongyloides stercoralis andcompared the results to Caenorhabditis elegans, a species that has an L3i-likedauer stage. Comparing S. stercoralis clusters with stage-specific expression toC. elegans homologs expressed in either dauer or non-dauer stages, matchesbetween S. stercoralis L1 and C. elegans non-dauer expressed genesdominated, suggesting conservation in the repertoire of genes expressed duringgrowth in nutrient-rich conditions. For example, S. stercoralis collagentranscripts were abundant in L1 but not L3i, a pattern consistent with C.elegans collagens. While a greater proportion of S. stercoralis L3i than L1genes have homologs among the C. elegans dauer-specific transcripts, we didnot uncover evidence for a robust conserved L3i / dauer ‘expression signature’.Strikingly, in comparisons of S. stercoralis clusters to C. elegans homologswith RNAi knockouts, those with significant L1-specific expression were morethan twice as likely as L3i-specific clusters to match genes with phenotypes.We also provide functional classifications of S. stercoralis clusters.