+44 330 818 7254Mbaye Tine, Heiner Kuhl
Calmodulin (CaM) is an ubiquitous Ca2+ binding protein that plays an important role in signalling events mediating the hormone secretion such as pituitary hormones. Previous laboratory experiments have demonstrated that this gene is relatively over expressed in gill tissues of Sarotherodon melanotheron acclimated to freshwater. In this study, the relationship between mRNA levels of the CaM in the gills and environmental salinity was investigated in wild populations of this species sampled during both the rainy and the dry season from six coastal, estuarine and freshwater sites in Senegal and Gambia. In both seasons the highest CaM mRNA levels were recorded in freshwater where the highest prolactin (PRL) and lowest growth hormone (GH) expression levels were previously reported. In the dry season CaM expression was highest at the lowest salinities (Guiers lake and Balingho) than in the hypersaline water sites of the Saloum estuary (Missirah, Foundiougne and Kaolack) and did not differ between these three sites. The amounts of CaM mRNA were not different between Balingho and Hann bay locations. The expression of CaM showed a similar pattern in rainy season, being highest in freshwater locations of Guiers lake and lowest in the most saline sites (Hann bay, Missirah, Foundiougne and Kaolack).The CaM mRNA levels were significantly negatively correlated with environmental salinity in both the rainy and the dry season. All together these results may indicate a role of CaM in the acclimation to hypo-osmotic stress possibly through the regulation of cell volume, calcium uptake and the expression of genes involved in osmoregulation such as PRL and GH. In the rainy season, overall mean expression of the CaM was higher than in the dry season, which may have reflected more variable particularly sudden fluctuations in salinity and poorer overall water quality.
Share this article