Evidence for the Functional Relevance of vgll3 and six6 οn Developmental Stages of Commercially Important Fish Species: Gilthead Seabream (Sparus aurata Linnaeus) and European Seabass (Dicentrarchus labrax Linnaeus)

The six6 and vgll3 genes play evolutionarily conserved roles in developmental processes and life history traits across species, including teleosts. Notable differences in genotype and allele frequencies of these genes have been observed between farmed and wild populations of European seabass and gilthead seabream, suggesting potential roles in traits associated with domestication. Here, we hypothesized that genetic variations in the six6 and vgll3 are associated with distinct expression profiles that underlie domestication-related traits in the two species. Using quantitative PCR (qPCR), we examined the expression profiles of these genes in early developmental stages across genotypes linked to domestication. Our results confirmed that vgll3 and six6 genotypes significantly influenced their expression in gilthead seabream, with statistically significant differences between genotypes. In European seabass, six6 expression did not significantly differ among genotypes, although heterozygous larvae showed higher variability that decreased at the juvenile stage. Meanwhile, no genetic variation was observed in vgll3, precluding genotype-specific expression analysis. Altogether, our findings provide the first evidence confirming that prior DNA-based associations of these genes with domestication traits are reflected at the mRNA level, particularly in vgll3 in gilthead seabream. This highlights the potential functional relevance of these genetic variations in shaping expression profiles linked to domestication in the species.