Variability in transcription levels of vitellogenin and other genes of interest in relation to gamete development in mussels Mytilus galloprovincialis (L.)

Gametogenesis represents the most critical step in reproduction and it is controlled by numerous endogenous and exogenous signals. Various environmental, chemical and hormonal factors, acting directly or indirectly, individually or in combination, have been proposed to cue, favor or modulate a suite of reproductive functions from the onset of gametogenesis to gamete release. In the present study, we analyzed the transcription levels of selected genes related to gametogenesis in mussels (Mytilus galloprovincialis) sampled in Plentzia (Bay of Biscay) along the reproductive cycle. Transcription levels of vitellogenin (vtg), vasa, estrogen receptor 1 (er1), Serotonin receptor (5-htr), cyclooxygenase (cox), vitelline coat lysine (vcl) andvitellineenvelope receptor for lysine (verl) were quantified by qRT-PCR in ovaries and testis of mussels at different gametogenic stages. Results obtained showed differences in transcription levels of selected genes between sexes and among different gametogenic stages, suggesting their potential role in the regulation of gametogenesis in M. galloprovincialis. vtg, cox, vcl and verl showed significant differences between males and females and among different gametogenic stages. Transcription of vasa and 5-htr did not differ between males and females, but among gametogenic stages. Vasa was highly transcribed at advanced stages of the gametogenic cycle, while 5-htr was up-regulated at early gametogenesis stages. Finally, transcription levels of er1 did not varied between males and females neither among gametogenic stages, suggesting that er1is constitutively regulated during gametogenesis in mussels.