Data from: Adaptation to deep-sea chemosynthetic environments as revealed by mussel genomes

Hydrothermal vents and methane seeps are extreme deep-sea ecosystems that
support dense populations of specialised macrobenthos such as mussels. But
lack of genome information hinders understanding of the adaptation of
these animals to such inhospitable environment. Here we report the genomes
of a deep-sea vent/seep mussel Bathymodiolus platifrons and a
shallow-water mussel Modiolus philippinarum. Phylogenetic analysis shows
that these mussel species diverged approximately 110.4 million years ago.
Many gene families, especially those for stabilising protein structures
and removing toxic substances from the cells, are greatly expanded in B.
platifrons, indicating adaptation to extreme environmental conditions. The
B. platifrons innate immune system is considerably more complex than that
of other lophotrochozoan species including M. philippinarum, with
significant expansion and high expression of gene families related to
immune recognition, endocytosis and caspase-mediated apoptosis in the
gill, revealing presumed genetic adaptation of the deep-sea mussel to the
presence of its chemoautotrophic endosymbionts. A follow-up metaproteomic
analysis of the gill of B. platifrons found methanotrophy, assimilatory
sulfate reduction, and ammonia metabolic pathways in the symbionts,
providing energy and nutrients to allow the host to thrive. Our study of
the genomic composition allowing symbiosis in extremophile molluscs gives
wider insights into the mechanisms of symbiosis in other organisms such as
deep-sea tubeworms and giant clams.