Heat shock transcription factor 1 (HSF1) plays an important role in regulating heat shock, which can activate heat shock proteins (HSPs). HSPs can protect organisms from thermal stress. Oysters in the intertidal zone can tolerate thermal stress. The Pacific oyster (Crassostrea gigas gigas) and Fujian oyster (C. gigas angulata)—allopatric subspecies with distinct thermal tolerances—make good study specimens for analyzing and comparing thermal stress regulation. We cloned and compared HSF1 isoforms, which is highly expressed under heat shock conditions in the two subspecies. The results revealed that two isoforms (HSF1a and HSF1d) respond to heat shock in both Pacific and Fujian oysters, and different heat shock conditions led to various combinations of isoforms. Subcellular localization showed that isoforms gathered in the nucleus when exposed to heat shock. The co-immunoprecipitation revealed that HSF1d can be a dimer. In addition, we selected HSPs that are expressed under the heat shock response, according to the RNA-seq and proteomic analyses. For the HSPs, we analyzed the coding part and the promoter sequences. The result showed that the domains of HSPs are conserved in two subspecies, but the promoters are significantly different. The Dual-Luciferase assay showed that the induced expression isoform HSF1d had the highest activity in C. gigas gigas, while the constitutively-expressed HSF1a was most active in C. gigas angulata. In addition, variation in the level of HSP promoters appeared to be correlated with gene expression. We argue that this gene is regulated based on the different expression levels between the two subspecies’ responses to heat shock. In summary, various stress conditions can yield different HSF1 isoforms and respond to heat shock in both oyster subspecies. Differences in how the isoforms and promoter are activated may contribute to their differential expressions. Overall, the results comparing C. gigas gigas and C. gigas angulata suggest that these isoforms have a regulatory relationship under heat shock, providing valuable information on the thermal tolerance mechanism in these commercially important oyster species.

热休克转录因子1（HSF1）在调节热休克中起重要作用，它可以激活热休克蛋白（HSPs）。HSP可以保护生物免受热应激。潮间带的牡蛎可以忍受热应力。太平洋牡蛎（Crassostrea gigas gigas）和福建牡蛎（C. gigas angulata）-具有不同热容限的异亚种-成为分析和比较热应力调节的良好研究样本。我们克隆并比较了HSF1亚型，该亚型在热冲击条件下在两个亚种中高度表达。结果表明，两种同工型（HSF1a和HSF1d）对太平洋和福建牡蛎的热激有响应，并且不同的热激条件导致了同工型的各种组合。亚细胞定位表明，当暴露于热激时，同工型聚集在细胞核中。免疫共沉淀显示HSF1d可以是二聚体。另外，我们选择了HSP根据RNA序列和蛋白质组学分析，它们在热激反应下表达。对于HSP，我们分析了编码部分和启动子序列。结果表明，热休克蛋白的结构域在两个亚种中是保守的，但启动子却有显着差异。双重萤光素酶检测显示，诱导的表达同工型HSF1d具有最高的活性。C. gigas gigas，而组成型表达的HSF1a在 C. gigas angulata。另外，水平的变化HSP启动子似乎与基因表达相关。我们认为该基因是基于两个亚种对热激反应的不同表达水平来调控的。总之，在两个牡蛎亚种中，各种胁迫条件都能产生不同的HSF1亚型，并对热激起反应。同工型和启动子如何激活的差异可能有助于它们的差异表达。总体来说，结果比较C. gigas gigas 和 C. gigas angulata 提示这些同工型在热冲击下具有调节关系，从而提供了关于这些商业上重要的牡蛎种的耐热机制的有价值的信息。