Molecular mechanisms of induced thermotolerance in two strains of Brachionus koreanus (Rotifera: Monogononta)

Abstract

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 and pinpoint some of the molecular mechanisms involved in the process. Exposure of organisms to 42 °C for 30 min, with a subsequent recovery at 25 °C for 8 h demonstrated to increase thermotolerance in up to three-fold when organisms were, in a posterior phase, subjected to a lethal temperature. This study also showed that one of the strains is tendentially more thermotolerant than the other. Indeed, NLHS exposure resulted in increased mRNA expression of different Hsp genes and production of HSP70 in general, but different patterns of expression were observed between strains. However, a single NLHS showed to have no effects in epigenetic mechanisms, suggesting that the induced capacity to tolerate heat stress was transient and some more cycles of NLHS may be needed to promote a persistent effect.