Schistosomiasis is a neglected tropical disease of humans caused by blood flukes of the genus Schistosoma, the only dioecious parasitic flatworms. Although aspects of sex determination, differentiation and reproduction have been studied in some Schistosoma species, almost nothing is known for Schistosoma japonicum, the causative agent of schistosomiasis japonica. This mainly reflects the lack of high-quality genomic and transcriptomic resources for this species. As current genomes for S. japonicum are highly fragmented, we assembled and report a chromosome-level reference genome (seven autosomes, the Z-chromosome and partial W-chromosome), achieving a substantially enhanced gene annotation. Utilising this genome, we discovered that the sex chromosomes of S. japonicum and its congener S. mansoni independently suppressed recombination during evolution, forming five and two evolutionary strata, respectively. By exploring the W-chromosome and sex-specific transcriptomes, we identified 35 W-linked genes and 257 female-preferentially transcribed genes (FTGs) from our chromosomal assembly and uncovered a signature for sex determination and differentiation in S. japonicum. These FTGs clustering within autosomes or the Z-chromosome exhibit a highly dynamic transcription profile during the pairing of female and male schistosomula, thereby representing a critical phase for the maturation of the female worms and suggesting distinct layers of regulatory control of gene transcription at this development stage. Collectively, these data provide a valuable resource for further functional genomic characterisation of S. japonicum, shed light on the evolution of sex chromosomes in this highly virulent human blood fluke, and provide a pathway to identify novel targets for development of intervention tools against schistosomiasis.
KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: We thank Prof. Zhao-Rong Lun for reading and commenting on the draft o f this manuscript. This work was supported by the National Key R&D Program of China 2018YFA0507300 and 2020YFC1200105; the National Natural Science Foundation of China (NSFC) 81630063, 81971959, 81971967,31671319, 31722050, 32061130208 and 81830066; the Natural Science Foundation of Zhejiang Province LD19C190001, the European Research Council Starting Grant 677696, and the Shanghai Blue Cross Brain Hospital Co., Ltd. and Shanghai Tongji University Education Development Foundation.Research at the University of Melbourne was supported by the Australian Research Council (ARC) (R.B.G. and N.D.Y.). Schistosomiasis research at QIMR Berghofer (D.P.M.) is supported by the National Health and Medical Research Council of Australia.
- Ecology, Evolution, Behavior and Systematics