Evolutionary Adaption to hydrothermal vent: A study of deep-sea-bivalve genome

Abstract

Oxygen depletion is an occurrence in an aquatic environment, where the concentration of dissolved oxygen decreases to the extent which can harm organisms dwelling within. Even short-term exposure to hypoxia can affect behavioral, physiological, biochemical, and molecular reactions of an organism, which can be lethal to most mammals including humans. If a low-oxygen condition persists for a period of time, cells utilize a transcription factor called HIF-1a to regulate the body’s oxygen homeostasis to protect itself from abiotic stress. Despite cell’s ability to cope with short-term exposure to hypoxia, in extreme conditions where oxygen levels are low in general (such as hydrothermal vents and cold seeps), only specialized organisms which have developed adaptation to hypoxia can survive. The goal of this study is to understand the molecular evolutionary process of the HIF-1a gene family in deep-sea environments. However, study on functional genes for adaption in these unique deep-sea environments is rare and genomic data is also scarce compared to terrestrial mammals. Additionally, most deep-sea organism researches focus on prokaryotes such as microbiome analysis or endosymbionts such as chemoautotrophic bacteria. To understand which genes play a pivotal role in survival of deep-sea organisms in extreme conditions, we generated the first genome sequence of five larvae (new species), presumably deep-sea bivalve. For comparative genomes, we annotated the HIF-1a genes from invertebrates including four deep-sea species and vertebrate fauna. We found that evolutionary pressure in deep-sea environments will lead to similar evolutionary directions in the HIF-1a gene across all taxa. Overall, this study sheds light on the HIF-1a adaptation of macrobenthos that inhabits the deep-sea hypoxic environment.