Abstract
BackgroundSchistosoma japonicum is one of the major causative agents of schistosomiasis. The pairing of males and females leads to female sexual maturation and maintains this mature state. However, the mechanisms by which pairing facilitates sexual maturation are yet to be investigated.MethodsParasites isolated from single- and double-sex cercariae-infected mice were analyzed by Solexa to uncover pair-regulated miRNA profiles. To reveal the biological functions of differentially expressed miRNAs among the samples, we predicted the target genes of these differentially expressed miRNAs and compared the gene expression between 23-d-old female schistosomula from double-sex infections (23DSI) and 23-d-old female schistosomula from single-sex infections (23SSI) by analyzing digital gene expression profiling (DGE). KEGG pathway analysis was used to investigate the relevant biological processes of these target genes to understand the significance of differentially expressed miRNAs after pairing.ResultsThe differentially expressed miRNA profiles of female 18- and 23-d post-single- and double-sex infections were analysed by Solexa. Similar miRNA profiles were observed in 18SSI and 18DSI, with the presence of identically expressed high-abundance miRNA, such as miRNA-1, miRNA-71b-5p and let-7. By contrast, in 23DSI and 23SSI, most of these high-abundance miRNAs were down-regulated. Furthermore, among all samples, bantam was distinctly up-regulated in 23 DSI, and miR-1, miR-71, miR-7-5p, and miR-7 were distinctly up-regulated in 23SSI. The transcriptomes of 23DSI and 23SSI revealed that the predicted target genes of miRNA-1, miRNA-71, miRNA-7, and miR-7-5p were associated with the ribonucleoprotein complex assembly and microtubule-based process. Conversely, the predicted target genes of bantam were related to the embryo development, development of primary sexual characteristics and regulation of transcription. KEGG pathway analysis revealed that in unpaired females, the highly-expressed miRNA-1, miRNA-71, miRNA-7, and miR-7-5p only inhibited the limited pathways, such as proteasome and ribosome assembly. Meanwhile, in paired mature females, highly-expressed bantam inhibited more biological pathways, such as the citrate cycle, glycolysis, fatty acid biosynthesis and RNA degradation.ConclusionsThe differentially expressed miRNAs between 23SSI and 23DSI and their different functions indicated that more genes or metabolic pathways in paired mature females were inhibited than those in unpaired ones. The results suggested that after pairing, specific miRNAs regulated gene expression to lead to female sexual maturation.
Highlights
Schistosoma japonicum is one of the major causative agents of schistosomiasis
Screening of miRNAs in S. japonicum from both single- and double-sex female worms at 18 d and 23 d post-infection To understand the effect of pairing on the development of female S. japonicum, we constructed cDNA libraries derived from 18–30 nt long RNAs isolated from both single- and double-sex female worms at 18 and 23 d post-infection
We sequenced the RNAs using an Illumina (Solexa) DNA sequencer, yielding a total of 14 333 070, 14 425 899, 14 624 020, and 12 268 947 clean reads corresponding to 98.92%, 97.27%, 99.07%, and 97.82% of high-quality reads for 18-d-old female schistosomula from 18DSI, 23-d-old female schistosomula from double-sex infections (23DSI), 18SSI, and 23-d-old female schistosomula from single-sex infections (23SSI), respectively
Summary
Schistosoma japonicum is one of the major causative agents of schistosomiasis. The pairing of males and females leads to female sexual maturation and maintains this mature state. The mechanisms by which pairing facilitates sexual maturation are yet to be investigated. Schistosomiasis is a chronic and debilitating parasitic disease caused by blood flukes of the genus Schistosoma. The drug resistance of the blood flukes to praziquantel has been reported [2]. Previous studies have proposed that male contact is necessary for ovary and vitelline gland development. This interaction is linked to the sexual maturation and maintenance of the mature state of females [8,9,10]. Females still need the constant pairing contact with males to reach sexual maturation. The mechanisms by which pairing facilitates female development are yet to be investigated
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