Meeting Abstract
Previous studies of transcriptomic responses to hypoosmotic exposure in blue mussels (Mytilus spp.) have suggested differential utilization of the amino acid ornithine among congeneric species. Ornithine catabolism is used to generate glutamate or proline through the activity of ornithine aminotransferase (OAT), or to create putrescine and other polyamines through activity of ornithine decarboxylase (ODC). Variation in expression of genes involved in ornithine metabolic pathways may help to explain differences in the salinity tolerances of M. galloprovincialis, M. trossulus, and M. edulis. This study was undertaken to better understand the potential role of OAT and ODC in blue mussels during exposure to altered salinity, as well as to examine the variation in gene expression across developmental stages and between species. We found that OAT gene expression increases during low salinity exposure in all three species, and that in M. edulis increased expression was associated with increased OAT enzyme activity. We observed that ODC tended to be downregulated during hypoosmotic exposure, although the response was typically smaller that that of OAT and inconsistent among individual mussels. During hyperosmotic stress, the patterns of expression of these two genes reversed, suggesting that synthesis of proline or glutamate is important during low salinity exposure but that polyamine synthesis may be more important during hyperosmotic exposure.
