Tissue-specific, temporal, and core gene-dependent expression patterns of Hsp70s reveal functional allocation in Chlamys farreri under heat stress.

Heat shock proteins 70 KDa (Hsp70s) engage in a broad spectrum of cellular functions in response to various stressors. Marine bivalves face substantial threats from the rising seawater temperature attributed to global warming. In the present study, expression patterns of Hsp70s in Zhikong scallop Chlamys farreri (CfHsp70s) were determined in embryos and larvae at all developmental stages, in healthy adult tissues, and across four various tissues exposed to high temperature for acute and chronic periods through in silico analysis. Spatiotemporal expressions suggested CfHsp70s performed specific functional differentiations in scallop's development and growth. Regulatory expression patterns of CfHsp70s, characterized by predominant down-regulation in the mantle, gill and hemocytes, as well as contrasting up-regulation in the heart, suggest differential functional allocation of CfHsp70s among tissues in response to heat stress. Particularly, a core set of 14 CfHsp70s, especially the nine members of the Hsp70B2s, characterized by gene expansion, intron-less structure, shorter gene length, preference for hydrophilic amino acids, and coordinated expression profiles, was predominantly responsible for the inducible up-regulations observed across all four tissue types. Collectively, the tissue-specific, temporal and core gene-dependent expression patterns of CfHsp70s illustrate the functional allocation and molecular evolution of Hsp70 family members in Zhikong scallops.