Abstract

The survival challenges faced by endemic ectothermic organisms of the perennially frigid Antarctic marine environment are well appreciated. The Antarctic notothenioid fishes must contend with two exacting environmental modalities – freezing seawater and high marine oxygenation. Underlying their cold-adaptive physiologies are genomic and gene expression changes crafted by millennia of these environmental selection forces. Nuclear gene expression changes are seen in highly augmented transcription of a set of protein gene families that operate in protein biosynthesis, protein folding and degradation, anti-oxidation, anti-apoptosis, innate immunity, and others, all of recognizable functional importance in mitigating stresses in the cold during notothenioid life histories. Many of these gene families have substantially expanded through gene duplication, providing large gene dosages for the observed transcriptional augmentations. The mitochondrial genome in Antarctic notothenioids and its role in mitochondrial energy production capacity are much less studied. We recently discovered a major mtDNA rearrangement that resulted in the translocation of the gene encoding the ND6 subunit of mt Complex I to the mt Control Region, as well as detected positive selection operating on the ND6 protein sequence. This highlights the importance of including the mt genome and mt proteins (mt and nuclear encoded) in evaluating mitochondrial capacities of Antarctic notothenioid in face of temperature and oxygenation changes in both evolutionary and short-term contexts. The growing body of genomic and gene expression data for Antarctic notothenioids provide informative entry points to experimental investigations of their cold-adaptive phenotypes (and thermal limits) at higher level of biological organizations.