Abstract
Meishan boars are known for their early sexual maturity. However, they exhibit a significantly smaller testicular size and a reduced proportion of Sertoli cells and daily sperm production compared with Duroc boars. The testes of Duroc and Meishan boars at 20, 75 and 270 days of age were used for histological and transcriptome analyses. Haematoxylin-eosin staining was conducted to observe histological structure of the testes in Duroc and Meishan boars at different ages. Although spermatogenesis occurred prior to 75 days in Meishan boars, the number of spermatogonia and Sertoli cells in Meishan boars were less than in Duroc boars at adulthood. The diameters of the seminiferous tubules of the testes differed significantly during the initiation of development of the seminiferous tubules between the two breeds. We obtained differentially expressed functional genes and analysed seven pathways involved in male sexual maturity and spermatogenesis using RNA-seq. We also detected four main alternative splicing events and many single nucleotide polymorphisms from testes. Eight functionally important genes were validated by qPCR, and Neurotrophin 3 was subjected to quantification and cellular localization analysis. Our study provides the first transcriptome evidence for the differences in sexual function development between Meishan and Duroc boars.
Highlights
Different breeds of boars have different sexual function and sperm production capacities
Few spermatogonia and Sertoli cells were found in 20-day-old Duroc and Meishan boars testes tissues, a larger number of spermatogonia and Sertoli cells were observed in the Meishan testes tissues
The first oestrus occurred during the age range of 56–84 days in Chinese Meishan boars compared with 120–180 days for conventional boars[1]; both breeds attained sexual maturity by 270 days of age
Summary
Different breeds of boars have different sexual function and sperm production capacities. The testis size, proportion of Sertoli cells and daily sperm production of Chinese Meishan boars is significantly smaller and lower than those of Duroc and Large White boars[1]. The diameter and number of seminiferous tubules, the number of interstitial and germ cells, the appearance of elongate spermatids, and spermatozoa in the seminiferous tubules can affect the initiation of male puberty development and normal spermatogenesis and sperm function, which alters male fertility. In order to reveal the histologic features and molecular mechanism that underlies the earlier sexual maturity of Meishan boars and the differences in sperm production among breeds, we performed a histological comparison by haematoxylin-eosin (HE) staining of paraffin sections and analysed the number of spermatogonia and Sertoli cells and diameters of the seminiferous tubules between the testes of Meishan and Duroc boars. Our results have shed new light on the boar sexual maturity and sperm production and provide new approaches for the development and utilization of superior genetic resources, and improve boar fertility which is important for pig industry
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