Molecular allocation of PC4s provides implications for deciphering thermal response in Zhikong scallop (Chlamys farreri)

The increasing sea temperature caused by global warming has led to serious death of Zhikong scallop (Chlamys farreri) and improving its thermal tolerance has become an active research area in scallop aquaculture industry. Gene transcriptional coactivator p15 (PC4) plays pivotally multi-faced roles in most vertebrates and some invertebrates, but the systematic identification and characterization of PC4 genes have less been reported in scallops. In this study, 15 PC4 genes (CfPC4s) were identified in Zhikong scallop through whole-genome scanning, including two pairs of tandem duplicate genes located in the same scaffold (CF-19495.9 and CF-19495.10, CF-6819.1 and CF-6819.2). Protein structural and phylogenetic analyses were performed to verify identities and evolutionary relationships of these genes. Spatiotemporal expression patterns were determined at different development stages and in healthy adult tissues, as well as expression regulations in selected tissues (mantles, gills, hemocytes and hearts) after high temperatures challenge (27 °C) with different durations (3 h, 6 h, 12 h, 24 h, 3 d, 6 d, 15 d and 30 d). Spatiotemporal expressions of CfPC4s were ubiquitous but exhibited different patterns, suggesting the functional roles of CfPC4s in all stages of growth and development of the scallop. Expression regulations of CfPC4s and their functional related factors (TFIIA, TFIID, TFIIH and RNAPII) in pre-initiation complex (PIC) in various tissues displayed up- and/or down-regulated responses at different time points, showing time- and/or tissue-dependent expression patterns with function allocation upon different thermal durations. Collectively, this study demonstrated that gene allocation of CfPC4s provided implications for deciphering thermal response in Zhikong scallop and potentially helped in developing strategies for long-term healthy sustainable Zhikong scallop culture.