Genome-wide sequencing identifies a thermal tolerance related synonymous mutation in the mussel Mytilisepta virgata

The roles of ‘silent’ synonymous mutations for organisms adapting to stressfully thermal environments are of fundamental biological and ecological interests but poorly understood. To study whether synonymous mutations influence the thermal adaptation of animals to heat stress at specific microhabitats, a genome-wide genotype-phenotype association analysis was carried out in the black mussels Mytilisepta virgata inhabiting different microhabitats. A synonymous mutation of Ubiquitin-specific Peptidase 15 (MvUSP15) was significantly associated with the physiological upper thermal limit of the mussel. The individuals carrying GG genotype (the G-type) at the mutant locus owned significantly lower heat tolerance compared to the individuals carrying GA and AA genotype (the A-type). Furthermore, when heated to sublethal temperature, the G-type exhibited higher inter-individual variations in the MvUSP15 expression, especially for the mussels on the sun-exposed microhabitats. Taken together, a sy...