Hypoxia at deep-sea hydrothermal vents represents one of the most basic challenges for metazoans, which then requires specific adaptations to acquire oxygen to meet their metabolic needs. Hydrothermal vent scale-worms (Polychaeta; Polynoidae) express large amounts of extracellular single- and multi-domain hemoglobins, in contrast with their shallow-water relatives that only possess intracellular globins in their nervous system (neuroglobins). We sequenced the gene encoding the single-domain (SD) globin from nine species of polynoids found in various vent and deep-sea reduced microhabitats (and associated constraints) to determine if the Polynoidae SD globins have been the targets of diversifying selection. Although extracellular, all the SD globins (and multi-domain ones) form a monophyletic clade that clusters within the intracellular globin group of other annelids, indicating that these hemoglobins have evolved from an intracellular myoglobin-like form. Positive selection could not be detected at the major ecological changes that the colonization of the deep-sea and hydrothermal vents represents. This suggests that no major structural modification was necessary to allow the globins to function under these conditions. The mere expression of these globins extracellularly may have been sufficiently advantageous for the polynoids living in hypoxic hydrothermal vents. Among hydrothermal vent species, positively selected amino acids were only detected in the phylogenetic lineage leading to the two mussel-commensal species (Branchipolynoe). In this lineage, the multiplicity of hemoglobins could have lessened the selective pressure on the SD hemoglobin, allowing the acquisition of novel functions by positive Darwinian selection. Conversely, the colonization of hotter environments (species of Branchinotogluma) does not seem to have required additional modifications.
Journal of Molecular Evolution – Springer Journals
Published: Nov 1, 2017
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera