Real-time quantitative PCR analysis of the effect of non-lethal heat shock in two strains of rotifer Brachionus sp.

Temperature plays an important role in the occurrence and performance of organisms in aquatic ecosystems and is also one of the main environmental factors affecting species’ survival and growth in aquaculture. As an important species for aquaculture sustainability, the rotifer Brachionus sp. benefits from inducible phenotypic traits that allow the organisms to cope with environmental stress. The exposure to high temperature has shown to increase production of heat shock proteins (HSPs) and histone modifications in several organisms, resulting in induced thermotolerance. This study aimed to evaluate the potential of non-lethal heat shock (NLHS) to induce thermotolerance in two strains of B. koreanus (MRS10 and IBA3) and pinpoint some of the molecular mechanisms involved in the process. For this, neonates were exposed to a 30 min NLHS, after which triplicates of heat shocked (NLHS treatment) and non-heat shocked (Reference treatment) organisms were placed under control conditions for 8 h. Sampling was done at 1 h, 4 h and 8 h, in each repliclate, to analyse gene expression of heat shock proteins and epigenetic-related genes. This was done for both rotifer strains studied. Results showed that, overall, induced thermotolerance was concomitant with a typical heat shock response, with up-regulation of HSP genes, after 1 and 4 h of recovery, especially seen for HSP40 and HSP90 for both strains. The exposure to a single NLHS did not promote significant alterations in the gene expression of several epigenetic markers.