Chief Science Correspondent
A team of South Korean, American and Australian researchers announced that they had successfully sequenced the genome of the Antarctic bullhead nothen, Notothenia coriiceps in an article published in Genomic Biology earlier this fall.
The paper marks the first full genome sequence of any Notothenioid, a suborder made up of 122 Antarctic fish species. Notothenioid members surround the Antarctic continent, comprising nearly half of the region's total fish species and accounting for 77 percent of the species diversity.
Antarctic fishes are somewhat of a mystery to evolutionary biologists. They have adapted to the extremely cold waters of the Southern Ocean, which can range from -2 to 10 degrees Celsius (28 to 50 degrees Fahrenheit). N. coriiceps can only survive in waters up to 6 degrees Celsius.
Through previous work, researchers have been able to gather genetic information on these animals by performing local analyses on gene variants for these traits. However, by mapping these organisms genomes, scientists will be able to track how and when these changes, scientists will be able to better calculate when and how these traits evolved. An entire genome sequence contains every piece of information for an organism's biological existence - every nucleotide base pair that accounts for the organism's physical and biochemical traits.
Scientists can split the DNA into genes, discreet regions that code for a particular trait. But genes often do not function on their own; they can be influenced by other genes or stretches of non-coding DNA. By examining the entire sequence, scientists can work to slowly to piece together the puzzle.
"We're providing the first global snapshot into the changes in notothenioid fish genomes that allowed the group to successfully exploit its environment. The genome is like a time capsule that records the evolutionary events associated with cold adaptation."
-H. William Detrich (co-author). Northeastern University
Examining the genomes of other organisms has provided greater insight into the evolutionary complexity of all life. Genomic analyses can be a useful tool in developing phylogenetic maps that track speciation and divergence throughout our evolutionary history. By comparing genomes across species, we can better understand how they are related and how certain traits came about on a molecular level. Mapping the genomes of the Antarctic fishes may be critical to demonstrating how these organisms' remarkable traits developed over their evolutionary history.
"We're providing the first global snapshot into the changes in notothenioid fish genomes that allowed the group to successfully exploit its environment," co-author H. William Detrich said in an interview published on Phys.org on Monday. "The genome is like a time capsule that records the evolutionary events associated with cold adaptation."
One of the most interesting findings in the N. coriiceps study involved changes in the heat shock response (HSR) following exposure to elevated temperatures. Nearly all organisms possess control of a set of heat shock proteins (HSPs) that are upregulated following exposure to elevated temperatures.
These proteins can function as chaperones, and prevent other proteins from misfolding or aggregating, which can be a concern at critically high temperatures. Thus, the HSR is essential in determining an organism's thermal plasticity. Current studies have reported conflicting data on whether Antarctic fishes possess an HSR. However, in this study, the team was able to determine that a number of HSPs were upregulated following exposure to critically high temperatures in this species. Interestingly, the researchers also found that many of these genes were also upregulated following exposure to critically low temperatures, suggesting that some HSPs are critical to preventing protein denaturatation at cold temperatures as well.
Studying the Antarctic fish genome is important because these organisms provide a unique opportunity to study marine evolution in an environment that has, at least for now, been relatively untouched by mankind. Notothenioids possess a gold mine of data for potential analysis in a habitat that cannot be replicated.
Writer's Note: I will be traveling to Palmer Station, Antarctica April 2015 to study N. coriiceps, along with two other Notothenioid species, as part of my dissertation at Ohio University. I will be documenting my journey and research online, and in the meantime I'll post semi-regular updates on Antarctic fish biology. I am very grateful to OU, my advisor and the National Science Foundation for this incredible opportunity. Stay updated by following me on Twitter (@ambiederman) or by reading my blog posts here.