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.温度在水生生态系统中生物的生存与机能发挥中扮演关键角色，同时也是水产养殖中影响物种存活与生长的核心环境因子之一。作为保障水产养殖可持续性的重要物种，臂尾轮虫属（Brachionus sp.）轮虫拥有可诱导的表型性状，可帮助个体应对环境胁迫。已有研究表明，高温暴露可促使多种生物合成热休克蛋白（heat shock proteins，HSPs）并发生组蛋白修饰，进而诱导机体产生耐热性。本研究旨在评估非致死热冲击（non-lethal heat shock，NLHS）诱导两株韩国臂尾轮虫（B. koreanus，MRS10与IBA3）产生耐热性的潜力，并阐明该过程涉及的部分分子机制。为此，研究人员将轮虫幼体置于非致死热冲击环境中处理30分钟；随后将经热冲击处理（NLHS处理组）与未经热冲击处理（对照组）的个体各设置三个生物学重复，置于正常培养条件下培养8小时。分别在培养1小时、4小时与8小时时对每个重复进行取样，以分析热休克蛋白与表观遗传相关基因的表达水平，本研究针对两种轮虫菌株均开展了上述实验。研究结果显示，总体而言，诱导产生的耐热性与典型的热休克反应相契合：在恢复培养1小时与4小时后，热休克蛋白基因出现上调表达，两株菌株的HSP40与HSP90基因均呈现出这一特征。单次非致死热冲击暴露并未使多种表观遗传标记物的基因表达产生显著变化。