Malic enzyme locus influences Atlantic salmon maturation probability in controlled conditions

Atlantic salmon life-histories are shaped by interactions between environmental and genetic factors. The mitochondrial NADP-dependent malic enzyme (me3 or mMEP-2), historically described as a polymorphic allozyme varying across populations, has been associated with age at maturity in wild populations. However, more recently, other loci (vgll3 and six6) have also been shown to influence age at maturity, and studies disentangling their relative effects are lacking. This is especially important given that me3 and vgll3 are located on the same chromosome. Here, we used a common-garden experiment to investigate the impact of the me3 locus on male parr maturation probability in a Finnish population whilst accounting for variation at the vgll3 and six6 loci. Although we found linkage disequilibrium between the me3 and vgll3 loci, me3 remained moderately associated with maturation probability even when vgll3 genotype was accounted for. Together, these results support observations from wild populations of a genetic effect of me3 on maturation probability, but they also highlight the importance of considering both me3 and vgll3 when investigating the mechanism linking these loci to maturation.