Abstract
BackgroundSchistosomiasis is one of the most prevalent parasitic diseases worldwide and is caused by parasitic trematodes of the genus Schistosoma. The pathogenesis of schistosomiasis is caused by eggs whose production is the consequence of the pairing of schistosomes and the subsequent sexual maturation of the female. Previous studies have demonstrated that protein kinases are involved in processes leading to the male-induced differentiation of the female gonads, ovary and vitellarium. Right open reading frame protein kinase 2 (RIOK-2) is a member of the atypical kinase family and shown in other organisms to be responsible for ribosomal RNA biogenesis and cell-cycle progression, as well as involves in nematode development. However, nothing is known about its functions in any trematode including schistosome.MethodsWe isolated and characterized the riok-2 gene from S. japonicum, and detected the transcriptional profiles of Sj-riok-2 by using real-time PCR and in situ hybridization. RNAi-mediated knockdown of Sj-riok-2 was performed, mitotic activities were detected by EdU incorporation assay and morphological changes on organs were observed by confocal laser scanning microscope (CLSM).ResultsIn silico analyses of the amino acid sequence of Sj-RIOK-2 revealed typical features of this class of kinases including a winged helix (wHTH) domain and a RIO kinase domain. Sj-riok-2 is transcribed in different developmental stages of S. japonicum, with a higher abundance in adult females and eggs. Localization studies showed that Sj-riok-2 was mainly transcribed in female reproductive organs. Experiments with adult schistosomes in vitro demonstrated that the transcriptional level of Sj-riok-2 was affected by pairing. Knocking down Sj-riok-2 by RNAi reduced cell proliferation in the vitellarium and caused the increased amount of mature oocytes in ovary and an accumulation of eggs within the uterus.ConclusionsSj-riok-2 is involved in the reproductive development and maturation of female S. japonicum. Our findings provide first evidence for a pairing-dependent role of Sj-riok-2 in the reproductive development and maturation of female S. japonicum. Thus this study contributes to the understanding of molecular processes controlling reproduction in schistosomes.
Highlights
IntroductionAs schistosomiasis is associated with granulomatous inflammatory responses in different host tissues, including liver, the intestinal tract and spleen (hepato-intestinal form) or the urinary bladder and/or genital tract (urogenital form), are induced by eggs deposited by female schistosomes [11], research efforts have focused on identifying processes responsible for growth and reproduction
Schistosomiasis is one of the most prevalent parasitic diseases worldwide and is caused by parasitic trematodes of the genus Schistosoma
Cloning and sequence analysis suggest that Sj-riok-2 is a member of the Right open reading frame (RIO)-kinase family The cDNA of Sj-riok-2 (GenBank: KY884990) is 2164 bp long, containing a 1476 bp open reading frame (ORF) that encodes 491 amino acids, a 344 bp 5′-UTR, and a 344 bp 3′-UTR including the poly-A tail preceded by a non-canonical poly-adenylation signal (ATTAAA) 40 bp upstream
Summary
As schistosomiasis is associated with granulomatous inflammatory responses in different host tissues, including liver, the intestinal tract and spleen (hepato-intestinal form) or the urinary bladder and/or genital tract (urogenital form), are induced by eggs deposited by female schistosomes [11], research efforts have focused on identifying processes responsible for growth and reproduction. The latter is of specific interest, because the pairing of females with male schistosomes is unique with respect to physiological consequences. Signal transduction processes have been detected to be involved in male-female interactions controlling oocyte and vitelline cell differentiation [15,16,17]
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