Abstract
BackgroundThe Asian seabass (Lates calcarifer) is a protandrous hermaphrodite that typically matures as a male at approximately 2–4 years of age and then changes sex in subsequent years. Although several sexual maturation stages have been described histologically for both testis and ovary, the underlying gene expression profiles remain lacking. The development of a gene expression platform is therefore necessary to improve our understanding of the gonad development of this cultured teleost species.MethodsThirty Asian seabass gonads were collected from farms in Singapore, examined histologically and staged according to their sex and gonadal maturation status. Partial coding sequences of 24 sex-related genes were cloned using degenerate primers and were sequenced. Additional 13 cDNA sequences were obtained through next-generation sequencing. A real-time qPCR was then performed using the microfluidic-based Fluidigm 48.48 Dynamic arrays.ResultsWe obtained 17 ovaries and 13 testes at various stages of sexual maturation. Of the 37 genes that were tested, 32 (86%) showed sexually dimorphic expression. These genes included sex-related genes, sox9, wt1, amh, nr5a2, dmrt1 and nr0b1, which showed testis-enhanced expression similar to other vertebrate species. Known male- and female-enhanced germ cells markers, which were established from studies in other species, similarly showed testis- and ovary-enhanced expression, respectively, in the Asian seabass. Three pro-Wnt signaling genes were also upregulated in the ovary, consistent with existing studies that suggested the role of Wnt signaling in ovarian differentiation in teleosts and mammals. The expression patterns of genes involved in steroidogenesis, retinoic acid metabolism, apoptosis and NF-κB signaling were also described. We were able to classify gonads according to sex and gonadal maturation stages, based on their small-scale transcriptomic profiles, and to uncover a wide variation in expression profiles among individuals of the same sex.ConclusionsThe analysis of a selected set of genes related to reproduction and in sufficient number of individuals using a qPCR array can elucidate new insights into the molecular mechanisms involved in Asian seabass gonad development. Given the conservation of gene expression patterns found in this study, these insights may also help us draw parallels with other teleosts.
Highlights
The Asian seabass (Lates calcarifer) is a protandrous hermaphrodite that typically matures as a male at approximately 2–4 years of age and changes sex in subsequent years
We were able to classify gonads according to sexual maturation status by hierarchical clustering analysis using expression profiles of these genes
Conserved expression patterns of sex-related genes and pathways in the Asian seabass with other teleosts and even mammals Known sex-related genes Among the genes in the array, there were genes with “pro-male” functions, such as amh, sox9, dmrt1, wt1, nr5a2 and nr0b1, which displayed conservation of testisenhanced expression in the Asian seabass that was similar to other vertebrates (Table 2)
Summary
The Asian seabass (Lates calcarifer) is a protandrous hermaphrodite that typically matures as a male at approximately 2–4 years of age and changes sex in subsequent years. The Asian seabass (Lates calcarifer), which is commonly known as barramundi, is a protandrous hermaphrodite This perciform teleost matures as a functional male at 2–4 years of age and subsequently changes sex to female at subsequent spawning seasons [1,2,3]. Due to this process, Asian seabass females are generally larger than males. The development of Asian seabass gonads has been well studied morphologically and histologically, the underlying molecular data regarding their development is lacking [1,2,3,4]. Next-generation sequencing technologies have only been recently used to provide functional genomics analyses of other aspects of the Asian seabass biology, such as temperature adaptation and the response to stress [5,6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
