Abstract
BackgroundThe Southern Ocean is the coldest ocean on Earth but a hot spot of evolution. The bottom-dwelling Eocene ancestor of Antarctic notothenioid fishes survived polar marine glaciation and underwent adaptive radiation, forming >120 species that fill all water column niches today. Genome-wide changes enabling physiological adaptations and the rapid expansion of the Antarctic notothenioids remain poorly understood.ResultsWe sequenced and compared 2 notothenioid genomes—the cold-adapted and neutrally buoyant Antarctic toothfish Dissostichus mawsoni and the basal Patagonian robalo Eleginops maclovinus, representing the temperate ancestor. We detected >200 protein gene families that had expanded and thousands of genes that had evolved faster in the toothfish, with diverse cold-relevant functions including stress response, lipid metabolism, protein homeostasis, and freeze resistance. Besides antifreeze glycoprotein, an eggshell protein had functionally diversified to aid in cellular freezing resistance. Genomic and transcriptomic comparisons revealed proliferation of selcys–transfer RNA genes and broad transcriptional upregulation across anti-oxidative selenoproteins, signifying their prominent role in mitigating oxidative stress in the oxygen-rich Southern Ocean. We found expansion of transposable elements, temporally correlated to Antarctic notothenioid diversification. Additionally, the toothfish exhibited remarkable shifts in genetic programs towards enhanced fat cell differentiation and lipid storage, and promotion of chondrogenesis while inhibiting osteogenesis in bone development, collectively contributing to the achievement of neutral buoyancy and pelagicism.ConclusionsOur study revealed a comprehensive landscape of evolutionary changes essential for Antarctic notothenioid cold adaptation and ecological expansion. The 2 genomes are valuable resources for further exploration of mechanisms underlying the spectacular notothenioid radiation in the coldest marine environment.
Highlights
Line 89-90: You specify "whole genome sequence analysis" as the criteria for mentioning the Antarctic rockcod as the only notothenioid reported so far, but Malmstrøm et al 2016 did publish genomic sequences and the assembly of Chaenocephalus aceratus
Reviewer #1: Review of "Genomic bases for colonizing the freezing Southern Ocean revealed by the genomes of Antarctic toothfish and Patagonia robalo" This manuscript sequences the genome and transcriptome of Antarctic tootfish and its closest temperate relative, the Patagonian robalo
I see that the authors have included the Antarctic bullhead notothen genome in their comparison analyses but do make fair comparison among the three notothenioid genomes
Summary
Line 89-90: You specify "whole genome sequence analysis" as the criteria for mentioning the Antarctic rockcod as the only notothenioid reported so far, but Malmstrøm et al 2016 (https://www.nature.com/articles/ng.3645) did publish genomic sequences and the assembly of Chaenocephalus aceratus. Reviewer #1: Review of "Genomic bases for colonizing the freezing Southern Ocean revealed by the genomes of Antarctic toothfish and Patagonia robalo" This manuscript sequences the genome and transcriptome of Antarctic tootfish and its closest temperate relative, the Patagonian robalo. L141: do the authors know why both the scaffold and contig N50 lengths are so much lower in robalo compared to toothfish?
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
