Differential Gene Expression in Liver, Gill, and Olfactory Rosettes of Coho Salmon (Oncorhynchus kisutch) After Acclimation to Salinity

Most Pacific salmonids undergo smoltification and transition from freshwater to saltwater, making various adjustments in metabolism, catabolism, osmotic, and ion regulation. The molecular mechanisms underlying this transition are largely unknown. In the present study, we acclimated coho salmon (Oncorhynchus kisutch) to four different salinities and assessed gene expression through microarray analysis of gills, liver, and olfactory rosettes. Gills are involved in osmotic regulation, liver plays a role in energetics, and olfactory rosettes are involved in behavior. Between all salinity treatments, liver had the highest number of differentially expressed genes at 1616, gills had 1074, and olfactory rosettes had 924, using a 1.5-fold cutoff and a false discovery rate of 0.5. Higher responsiveness of liver to metabolic changes after salinity acclimation to provide energy for other osmoregulatory tissues such as the gills may explain the differences in number of differentially expressed genes. Differentially expressed genes were tissue- and salinity-dependent. There were no known genes differentially expressed that were common to all salinity treatments and all tissues. Gene ontology term analysis revealed biological processes, molecular functions, and cellular components that were significantly affected by salinity, a majority of which were tissue-dependent. For liver, oxygen binding and transport terms were highlighted. For gills, muscle, and cytoskeleton-related terms predominated and for olfactory rosettes, immune response-related genes were accentuated. Interaction networks were examined in combination with GO terms and determined similarities between tissues for potential osmosensors, signal transduction cascades, and transcription factors

Genetic Inactivation of European Sea Bass (Dicentrarchus labrax L.) Eggs Using UV-Irradiation: Observations and Perspectives

International audienceAndrogenesis is a form of uniparental reproduction leading to progenies inheriting only the paternal set of chromosomes. Ithas been achieved with variable success in a number of freshwater species and can be attained by artificial fertilization ofgenetically inactivated eggs following exposure to gamma (c), X-ray or UV irradiation (haploid androgenesis) and byrestoration of diploidy by suppression of mitosis using a pressure or thermal shock. The conditions for the geneticinactivation of the maternal genome in the European sea bass (Dicentrarchus labraxL.) were explored using differentcombinations of UV irradiation levels and durations. UV treatments significantly affected embryo survival and generated awide range of developmental abnormalities. Despite the wide range of UV doses tested (from 7.2 to 720 mJ.cm22), only onedose (60 mJ.cm22.min21with 1 min irradiation) resulted in a small percentage (14%) of haploid larvae at hatching in theinitial trials as verified by flow cytometry. Microsatellite marker analyses of three further batches of larvae produced by usingthis UV treatment showed a majority of larvae with variable levels of paternal and maternal contributions and only one larvadisplaying pure paternal inheritance. The results are discussed also in the context of an assessment of the UV-absorbancecharacteristics of egg extracts in this species that revealed the presence of gadusol, a compound structurally related tomycosporine-like amino acids (MAAs) with known UV-screening properties

Sex-change and gonadal steroids in sequentially-hermaphroditic teleost fish

Sex-change is an intriguing phenomenon that is common among certain groups of teleost fishes. The process itself has a number of independent origins, although in each case it is initiated and (or) regulated by gonadal steroids. Despite the commercial importance of sex-change technology to fish culturists, our understanding of the relationship between steroids and sex-change is, at best, rudimentary. In this paper I review the current state of knowledge concerning (a) which steroids are involved, (b) how such steroids mediate sex-change, and (c) how steroidogenesis is regulated during gonadal transition. I conclude that the steroidal endocrinology of sex-change is multifarious and species specific – a result which challenges the relative stability of vertebrate endocrine axes, but one which probably reflects the independent evolution of this adaptation