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

Functional allocation of Mitogen-activated protein kinases (MAPKs) unveils thermotolerance in scallop Argopecten irradians irradians

Global warming has significantly impacted agriculture, particularly in animal husbandry and aquaculture industry. Rising ocean temperatures due to global warming are severely affecting shellfish production, necessitating an understanding of how shellfish cope with thermal stress. The mitogen-activated protein kinases (MAPK) signaling pathway plays a crucial role in cell growth, differentiation, adaptation to environmental stress, inflammatory response, and managing high temperature stress. To investigate the function of MAPKs in bay scallops, a comparative genomics and bioinformatics approach identified three MAPK genes: AiERK, Aip38, and AiJNK. Structural and phylogenetic analyses of these proteins were conducted to determine their evolutionary relationships. Spatiotemporal expression patterns were examined at different developmental stages and in various tissues of healthy adult scallops. Additionally, the expression regulation of these genes was studied in selected tissues (hemocyte, gill, heart, mantle) following exposure to high temperatures (32 °C) for different durations (0 h, 6 h, 12 h, 24 h, 3 d, 6 d, 10 d). The spatiotemporal expressions of AiMAPKs were ubiquitous, with significant increases in AiERK expression observed at the umbo larval stage (3.09-fold), while Aip38 and AiJNK were identified as potential maternal effect genes. In adult scallops, different gene expression patterns of AiMAPKs were observed across eight tissues, with high expressions in the foot and gill, and lower expressions in the striated muscle. Following high temperature stress, AiMAPKs expressions in the gill and mantle were mainly up-regulated, while in the hemocyte, they were primarily down-regulated. These findings indicate time- and tissue-dependent expression patterns with functional allocation in response to different thermal durations. This study enhances our understanding of the function and evolution of AiMAPKs genes in shellfish and provides a theoretical basis for elucidating the energy regulation mechanism of bay scallops in response to high temperature stress.

Tissue-Specific and Time-Dependent Expressions of PC4s in Bay Scallop (Argopecten irradians irradians) Reveal Function Allocation in Thermal Response

Transcriptional coactivator p15 (PC4) encodes a structurally conserved but functionally diverse protein that plays crucial roles in RNAP-II-mediated transcription, DNA replication and damage repair. Although structures and functions of PC4 have been reported in most vertebrates and some invertebrates, the PC4 genes were less systematically identified and characterized in the bay scallop Argopecten irradians irradians. In this study, five PC4 genes (AiPC4s) were successfully identified in bay scallops via whole-genome scanning through in silico analysis. Protein structure and phylogenetic analyses of AiPC4s were conducted to determine the identities and evolutionary relationships of these genes. Expression levels of AiPC4s were assessed in embryos/larvae at all developmental stages, in healthy adult tissues and in different tissues (mantles, gills, hemocytes and hearts) being processed under 32 °C stress with different time durations (0 h, 6 h, 12 h, 24 h, 3 d, 6 d and 10 d). Spatiotemporal expression profiles of AiPC4s suggested the functional roles of the genes in embryos/larvae at all developmental stages and in healthy adult tissues in bay scallop. Expression regulations (up- and down-) of AiPC4s under high-temperature stress displayed both tissue-specific and time-dependent patterns with function allocations, revealing that AiPC4s performed differentiated functions in response to thermal stress. This work provides clues of molecular function allocation of PC4 in scallops in response to thermal stress and helps in illustrating how marine bivalves resist elevated seawater temperature.