@article {8133, title = {Gonadal transcriptomes associated with sex phenotypes provide potential male and female candidate genes of sex determination or early differentiation in Crassostrea gigas, a sequential hermaphrodite mollusc.}, journal = {BMC Genomics}, volume = {22}, year = {2021}, month = {2021 Aug 09}, pages = {609}, abstract = {

BACKGROUND: In the animal kingdom, mollusca is an important phylum of the Lophotrochozoa. However, few studies have investigated the molecular cascade of sex determination/early gonadal differentiation within this phylum. The oyster Crassostrea gigas is a sequential irregular hermaphrodite mollusc of economic, physiological and phylogenetic importance. Although some studies identified genes of its sex-determining/-differentiating pathway, this particular topic remains to be further deepened, in particular with regard to the expression patterns. Indeed, these patterns need to cover the entire period of sex lability and have to be associated to future sex phenotypes, usually impossible to establish in this sequential hermaphrodite. This is why we performed a gonadal RNA-Seq analysis of diploid male and female oysters that have not changed sex for 4 years, sampled during the entire time-window of sex determination/early sex differentiation (stages 0 and 3 of the gametogenetic cycle). This individual long-term monitoring gave us the opportunity to explain the molecular expression patterns in the light of the most statistically likely future sex of each oyster.

RESULTS: The differential gene expression analysis of gonadal transcriptomes revealed that 9723 genes were differentially expressed between gametogenetic stages, and 141 between sexes (98 and 43 genes highly expressed in females and males, respectively). Eighty-four genes were both stage- and sex-specific, 57 of them being highly expressed at the time of sex determination/early sex differentiation. These 4 novel genes including Trophoblast glycoprotein-like, Protein PML-like, Protein singed-like and PREDICTED: paramyosin, while being supported by RT-qPCR, displayed sexually dimorphic gene expression patterns.

CONCLUSIONS: This gonadal transcriptome analysis, the first one associated with sex phenotypes in C. gigas, revealed 57 genes highly expressed in stage 0 or 3 of gametogenesis and which could be linked to the future sex of the individuals. While further study will be needed to suggest a role for these factors, some could certainly be original potential actors involved in sex determination/early sex differentiation, like paramyosin and could be used to predict the future sex of oysters.

}, keywords = {Animals, Crassostrea, Female, Gene Expression Profiling, Gonads, Humans, Male, Phenotype, Phylogeny, Sex Differentiation, Transcriptome}, issn = {1471-2164}, doi = {10.1186/s12864-021-07838-1}, author = {Broquard, Coralie and Saowaros, Suwansa-Ard and Lepoittevin, M{\'e}lanie and Degremont, Lionel and Lamy, Jean-Baptiste and Morga, Benjamin and Elizur, Abigail and Anne-Sophie Martinez} } @article {3701, title = {Direct evidence for maternal inheritance of bacterial symbionts in small deep-sea clams (Bivalvia: Vesicomyidae).}, journal = {Naturwissenschaften}, volume = {101}, year = {2014}, month = {2014 May}, pages = {373-83}, abstract = {

Bacterial symbiont transmission is a key step in the renewal of the symbiotic interaction at each host generation, and different modes of transmission can be distinguished. Vesicomyidae are chemosynthetic bivalves from reducing habitats that rely on symbiosis with sulfur-oxidizing bacteria, in which two studies suggesting vertical transmission of symbionts have been published, both limited by the imaging techniques used. Using fluorescence in situ hybridization and transmission electron microscopy, we demonstrate that bacterial symbionts of Isorropodon bigoti, a gonochoristic Vesicomyidae from the Guiness cold seep site, occur intracellularly within female gametes at all stages of gametogenesis from germ cells to mature oocytes and in early postlarval stage. Symbionts are completely absent from the male gonad and gametes. This study confirms the transovarial transmission of symbionts in Vesicomyidae and extends it to the smaller species for which no data were previously available.

}, keywords = {Animals, Bacterial Physiological Phenomena, Bivalvia, Female, Germ Cells, Gonads, In Situ Hybridization, Fluorescence, Male, Microscopy, Electron, Transmission, Oceans and Seas, Symbiosis}, issn = {1432-1904}, doi = {10.1007/s00114-014-1165-3}, author = {Szafranski, Kamil M and Sylvie M Gaudron and S{\'e}bastien Duperron} } @article {3639, title = {Neuroendocrine gene expression reveals a decrease in dopamine D2B receptor with no changes in GnRH system during prepubertal metamorphosis of silvering in wild Japanese eel.}, journal = {Gen Comp Endocrinol}, volume = {206}, year = {2014}, month = {2014 Sep 15}, pages = {8-15}, abstract = {

Silvering is a prepubertal metamorphosis preparing the eel to the oceanic reproductive migration. A moderate gonad development occurs during this metamorphosis from the sedentary yellow stage to the migratory silver stage. The aim of this study was to elucidate the molecular aspects of various endocrine parameters of BPG axis at different ovarian developmental stages in wild yellow and silver female Japanese eels. The GSI of the sampled female eels ranged between 0.18 and 2.3\%, corresponding to yellow, pre-silver and silver stages. Gonad histology showed changes from previtellogenic oocytes in yellow eels to early vitellogenic oocytes in silver eels. Both serum E2 and T concentrations significantly increased with ovarian development indicating a significant activation of steroidogenesis during silvering. In agreement with previous studies, significant increases in pituitary gonadotropin beta subunits FSH-β and LH-β transcripts were also measured by qPCR, supporting that the activation of pituitary gonadotropin expression is likely responsible for the significant ovarian development observed during silvering. We investigated for the first time the possible brain neuroendocrine mechanisms involved in the activation of the pituitary gonadotropic function during silvering. By analyzing the expression of genes representative of the stimulatory GnRH control and the inhibitory dopaminergic control. The transcript levels of mGnRH and the three GnRH receptors did not change in the brain and pituitary between yellow and silver stages, suggesting that gene expression of the GnRH system is not significantly activated during silvering. The brain transcript levels of tyrosine hydroxylase, limiting enzyme of DA synthesis did not change during silvering, indicating that the DA synthesis activity was maintained. In contrast, a significant decrease in DA-D2B receptor expression in the forebrain and pituitary was observed, with no changes in DA-D2A receptor. The decrease in the pituitary expression of DA-D2BR during silvering would allow a reduced inhibitory effect of DA. We may raise the hypothesis that this regulation of D2BR gene expression is one of the neuroendocrine mechanisms involved in the slight activation of the pituitary gonadotropin and gonadal activity that occur at silvering.

}, keywords = {Animals, Cells, Cultured, Dopamine, Eels, Female, Follicle Stimulating Hormone, beta Subunit, Gene Expression Regulation, Gonadotropin-Releasing Hormone, Immunoblotting, Immunoenzyme Techniques, Luteinizing Hormone, beta Subunit, Metamorphosis, Biological, Neurosecretory Systems, Oocytes, Ovary, Real-Time Polymerase Chain Reaction, Receptors, Dopamine D2, Reproduction, Reverse Transcriptase Polymerase Chain Reaction, RNA, Messenger, Sexual Maturation, Skin Pigmentation}, issn = {1095-6840}, doi = {10.1016/j.ygcen.2014.08.001}, author = {Jeng, Shan-Ru and Wen-Shiun Yueh and Pen, Yi-Ting and Lee, Yan-Horn and Chen, Guan-Ru and Sylvie Dufour and Chang, Ching-Fong} } @article {3486, title = {New Sicydiinae phylogeny (Teleostei: Gobioidei) inferred from mitochondrial and nuclear genes: insights on systematics and ancestral areas.}, journal = {Mol Phylogenet Evol}, volume = {70}, year = {2014}, month = {2014 Jan}, pages = {260-71}, abstract = {

The Sicydiinae subfamily (Teleostei: Gobioidei) is the biggest contributor to the diversity of fish communities in river systems of tropical islands. These species are found in the Indo-Pacific area, the Caribbean region and West Africa. They spawn in freshwater, their planktotrophic larvae drift downstream to the sea where they develop, before returning to the rivers to grow and reproduce. Hence, they are called amphidromous. Their phylogeny has been explored using a total of 3545 sites from 5 molecular markers (mitochondrial DNA: 16S rDNA, cytochrome oxidase I, cytochrome b; nuclear DNA: rhodopsin gene and a nuclear marker specially developed for this study, the interferon regulatory factor 2 binding protein 1-IRF2PB1). Sequences were obtained for 59 Sicydiinae specimens of 9 known genera. The Bayesian and maximum likelihood analyses support the monophyly of the subfamily as well as the monophylyof all genera except Sicydium, which is paraphyletic. Five major clades were identified within this subfamily. One clade contained the genus Stiphodon. Another clade contained Sicyopterus, Sicydium and Parasicydium with Sicyopterus as sister genus of Sicydium. The non-monophyly of Sicydium subclade, because it includes the monotypic genus Parasicydium, challenged the validity of Parasicydium genus. Ancestral area reconstruction showed that the subfamily emerged in the Central West Pacific region implying that previous hypotheses proposing a dispersal route for Sicydiinae into the Atlantic Ocean are unsupported by the present analysis. Our results suggest that the hypotheses for the dispersal route of the genus Sicydium should be reconsidered.

}, keywords = {Animals, Bayes Theorem, Cell Nucleus, Cytochromes b, DNA, Mitochondrial, DNA, Ribosomal, Electron Transport Complex IV, Evolution, Molecular, Female, Mitochondria, Perciformes, Phylogeny, Sequence Analysis, DNA}, issn = {1095-9513}, doi = {10.1016/j.ympev.2013.09.026}, author = {Taillebois, Laura and Castelin, Magalie and Clara Lord and Chabarria, Ryan and Dettai, Agn{\`e}s and Philippe Keith} }