Exploring the genomic underpinnings of symbiosis in bobtail squid

January 3 – Febuary 28, 2021

Meeting Abstract

S2-4  Mon Jan 4 11:30 – 12:00  Exploring the genomic underpinnings of symbiosis in bobtail squid Heath-Heckman, EAC*; Nishiguchi, M; Michigan State University; University of California, Merced each@msu.edu

Due to their large size (~3.5 Gb) and high repetitive content, cephalopod genomes have long been difficult to study. However, with the recent sequencing of several cephalopod genomes, including the Hawaiian bobtail squid (Euprymna scolopes), whole-genome studies of these molluscs are now possible. Of particular interest are the sepiolid (bobtail) squids, many of which develop photophores in which bioluminescent bacterial symbionts reside. The variable presence of the symbiosis across the group allows us to determine regions of the genome that are under selection in symbiotic lineages, potentially providing a mechanism for identifying genes instrumental in the evolution of these mutualistic associations. To this end, we have used high-throughput sequencing to generate seven bobtail squid genomes, six of which maintain symbioses with luminescent bacteria (E. scolopes, E. tasmanica, E. hyllebergi, E. albatrossae, Sepiola affinis, and Rondeletiola minor), and one of which does not (Sepietta neglecta). Using Abyss-2.0 and then Chromosomer with the published E. scolopes genome as a template, we generated genomes of about 76-79% completeness. For S. neglecta, we were able to generate a more complete genome using Illumina reads, Nanopore sequencing, and Omni-C proximity ligation. The data we have generated will enable whole-genome comparisons between these species to determine gene and regulatory content that differs between symbiotic and non-symbiotic lineages, as well as genes associated with symbiosis that are under selection. Our study is, to our knowledge, the first family-level genome comparison within the cephalopoda, and will greatly add to our knowledge of both genome dynamics within the sepiolid squid and the mechanisms in which genomes evolve to accommodate microbial symbioses.

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