Characterization and expression patterns of the Fox gene family under heat and cold stress in Manila clam Ruditapes philippinarum based on genome-wide identification

In this study, the Fox gene family of Ruditapes philippinarum was identified by bioinformatics analysis and genome data. The results showed that a total of 21 Fox genes were identified in R. philippinarum, which were divided into 16 subfamilies, including two members of Foxa subfamily (Foxa1, Foxa2), three members of Foxl subfamily (Foxl1b, Foxl1a, FOXL2), three members of Foxn subfamily (FOXN3, FOX4A, Foxn4b) and one member of other families. The chromosome distribution, domains, conserved motifs, introns, exons and protein tertiary structures of these 21 Fox genes were predicted. By analyzing the RNA-seq data of R. philippinarum, it was found that the Fox gene family was differentially expressed in different tissues, different developmental stages and under heat and cold stress. Most of Fox genes were highly expressed in four tissues: labial palp, gonad, gill and foot. Most of the Fox genes were highly expressed in blastula stage. Most of the Fox genes were highly expressed in high temperature group of two populations, and Foxo, FOXG1 were highly expressed in low temperature group. In addition, qPCR showed that the expression levels of Foxo and Foxj1b genes increased significantly under acute cold stress. Therefore, we speculate that Fox genes may play important roles in embryo development and the temperature stress of R. philippinarum, and this study provides a basis for further exploring the molecular mechanism of low temperature tolerance mediated by Fox.