A Unique Mitochondrial Gene Block Inversion in Antarctic Trematomin Fishes: A Cautionary Tale

Area of Science:

• Evolutionary Biology
• Genomics
• Marine Biology

Background:

• Antarctic notothenioid fishes exhibit notable mitochondrial (mt) genome rearrangements.
• Understanding these rearrangements is key to studying fish evolution in extreme environments.

Purpose of the Study:

• To sequence and analyze the complete mitochondrial genomes of three Trematomini notothenioids: bald notothen, spotted notothen, and emerald notothen.
• To compare their mt genome structure with other Antarctic fish, specifically Pleuragramma antarctica.

Main Methods:

• Mitochondrial genomes were sequenced using next-generation Illumina technology.
• Assembly verification was performed using Sanger sequencing.
• Comparative analysis of gene order and identification of intergenic spacers were conducted.

Main Results:

• Complete mt genomes of bald notothen, spotted notothen, and emerald notothen were successfully sequenced and verified.
• A significant gene inversion, involving multiple genes and the control region, was identified in the three trematomin mt genomes compared to P. antarctica.
• Three intergenic spacers were found in the trematomin mt genomes, potentially indicating past gene duplications.

Conclusions:

• The study confirms major mitochondrial genome rearrangements in Antarctic notothenioids, specifically a large gene inversion in the Trematomini tribe.
• The findings highlight the importance of assembly verification when using next-generation sequencing for mitochondrial genome studies.
• These genomic insights contribute to understanding the evolutionary adaptations of Antarctic fish.