Abstract
Despite the great advances in sequencing technologies, genomic and transcriptomic information for marine non-model species with ecological, evolutionary, and economical interest is still scarce. In this work we aimed to identify genes expressed during spermatogenesis in the functional hermaphrodite scallop Nodipecten subnodosus (Mollusca: Bivalvia: Pectinidae), with the purpose of obtaining a panel of genes that would allow for the study of differentially transcribed genes between diploid and triploid scallops in the context of meiotic arrest and reproductive sterility. Because our aim was to isolate genes involved in meiosis and other testis maturation-related processes, we generated suppressive subtractive hybridization libraries of testis vs. inactive gonad. We obtained 352 and 177 ESTs by clone sequencing, and using pyrosequencing (454-Roche) we maximized the identified ESTs to 34,276 reads. A total of 1,153 genes from the testis library had a blastx hit and GO annotation, including genes specific for meiosis, spermatogenesis, sex-differentiation, and transposable elements. Some of the identified meiosis genes function in chromosome pairing (scp2, scp3), recombination and DNA repair (dmc1, rad51, ccnb1ip1/hei10), and meiotic checkpoints (rad1, hormad1, dtl/cdt2). Gene expression analyses in different gametogenic stages in both sexual regions of the gonad of meiosis genes confirmed that the expression was specific or increased towards the maturing testis. Spermatogenesis genes included known testis-specific ones (kelch-10, shippo1, adad1), with some of these known to be associated to sterility. Sex differentiation genes included one of the most conserved genes at the bottom of the sex-determination cascade (dmrt1). Transcript from transposable elements, reverse transcriptase, and transposases in this library evidenced that transposition is an active process during spermatogenesis in N. subnodosus. In relation to the inactive library, we identified 833 transcripts with functional annotation related to activation of the transcription and translation machinery, as well as to germline control and maintenance.
Highlights
The Pacific lion-paw scallop Nodipecten subnodosus is a functional hermaphrodite Pectinidae species
We found 2,037 sequences with at least one significant blastx hit corresponding to 16.9%; and within those, 51% of the top-blast hits were against proteins of Crassostrea gigas, a bivalve mollusk species with a recently sequenced genome [46]
With regard to each specific library, 1,153 transcripts from the late maturing testis and 833 from the inactive gonad library had a significant blast hit against the nr Genbank database (Table S2), and from those numbers, 768 (67%) and 697 (84%) respectively, had at least one Gene Ontology term significantly associated by blast2go (Table S3)
Summary
The Pacific lion-paw scallop Nodipecten subnodosus is a functional hermaphrodite Pectinidae species It is considered the largest harvested scallop in the American continent, reaching a shell length of 16 cm. It is characterized by a clear and marked organ differentiation [1] in contrast to most non-pectinid bivalves, including the gonad that is a distinctly separated organ, and composed of ovary and testis parts (see Fig. 1 in [2]). The discovery of reproductive genes in a Pectinidae species as N. subnodosus will offer the opportunity for further studies on the genetics of functional hermaphroditism, from germ cells maintenance to sex differentiation, as well as gamete differentiation through meiosis
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
