Deep sea is characterized by high hydrostatic pressure, limited food, and cold. Understanding how animals adapt to this harsh environment is of great scientific interest. Of the animals dwelling in the deep sea, Hirondellea gigas is a dominant animal resident living in the world deepest point, Challenger Deep (~11,000m depth) of the Mariana Trench, and Aldrovandia affinis fish is a typical deep sea cosmopolitan species. In the present study, we performed transcriptome sequencing of the amphipod Hirondellea gigas collected at a depth of 10,929 m from the East Pond of the Challenger Deep and the fish Aldrovandia affinis captured by Remotely Operated Vehicle from Noho site of Okinawa Trough at the depth of 1550 m.

Positive selection analysis of 5659 single copy orthologous genes of H. g...[ Read more ]

Deep sea is characterized by high hydrostatic pressure, limited food, and cold. Understanding how animals adapt to this harsh environment is of great scientific interest. Of the animals dwelling in the deep sea, Hirondellea gigas is a dominant animal resident living in the world deepest point, Challenger Deep (~11,000m depth) of the Mariana Trench, and Aldrovandia affinis fish is a typical deep sea cosmopolitan species. In the present study, we performed transcriptome sequencing of the amphipod Hirondellea gigas collected at a depth of 10,929 m from the East Pond of the Challenger Deep and the fish Aldrovandia affinis captured by Remotely Operated Vehicle from Noho site of Okinawa Trough at the depth of 1550 m.

Positive selection analysis of 5659 single copy orthologous genes of H. gigas and 5548 single copy orthologous genes of A. affinis clearly identified that 62 positively selected genes in the H. gigas lineage and 262 genes in the A. affinis lineage. Both of them contain cold shock genes related to genetic information processing and genes involving in DNA repair. Moreover, positively selected genes of H. gigas includes genes related to β-alanine biosynthesis, energy metabolism, and that of fish contains genes associated to regulating cytoskeleton system.

For multiple copy orthologous genes of H. gigas, gene family expansion analysis revealed that cold-inducible proteins (i.e. transcription factors II A and transcription elongation factor 1) as well as zinc finger domains are expanded in H. gigas.

Overall, our results indicate that genetic adaptation to the deep sea environment may be mediated by gene family expansion and amino acid substitutions of specific proteins. Additionally, high quality transcriptomes of hadal amphipod and deep sea fish was provided for future deep sea studies.