Transcriptional profiles in Strongyloides stercoralis males reveal deviations from the Caenorhabditis sex determination model

Abstract

AbstractThe human and canine parasitic nematodeStrongyloides stercoralisutilizes an XX/XO sex determination system, with parasitic females reproducing by mitotic parthenogenesis and free-living males and females reproducing sexually. However, the genes controllingS. stercoralissex determination and male development are unknown. We observed precocious development of rhabditiform males in permissive hosts treated with corticosteroids, suggesting that steroid hormones can regulate male development. To examine differences in transcript abundance between free-living adult males and other developmental stages, we utilized RNA-Seq. We found two clusters ofS. stercoralis-specific genes encoding predicted transmembrane proteins that are only expressed in free-living males. We additionally identified homologs of several genes important for sex determination inCaenorhabditisspecies, includingmab-3,tra-1,fem-2, andsex-1, which may have similar functions. However, we identified three paralogs ofgld-1;Ss-qki-1transcripts were highly abundant in adult males, whileSs-qki-2andSs-qki-3transcripts were highly abundant in adult females. We also identified paralogs of pumilio domain-containing proteins with sex-specific transcripts. Intriguingly,her-1appears to have been lost in several parasite lineages, and we were unable to identify homologs oftra-2outside ofCaenorhabditisspecies. Together, our data suggest that different mechanisms control male development inS. stercoralisandCaenorhabditisspecies.