RESEARCH ARTICLE The whale shark genome reveals patterns of vertebrate gene family evolution Milton Tan1*, Anthony K Redmond2, Helen Dooley3, Ryo Nozu4, Keiichi Sato4,5, Shigehiro Kuraku6, Sergey Koren7, Adam M Phillippy7, Alistair DM Dove8, Timothy Read9 1Illinois Natural History Survey at University of Illinois Urbana-Champaign, Champaign, United States; 2Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland; 3University of Maryland School of Medicine, Institute of Marine & Environmental Technology, Baltimore, United States; 4Okinawa Churashima Research Center, Okinawa Churashima Foundation, Okinawa, Japan; 5Okinawa Churaumi Aquarium, Motobu, Okinawa, Japan; 6RIKEN Center for Biosystems Dynamics Research (BDR), RIKEN, Kobe, Japan; 7National Human Genome Research Institute, National Institutes of Health, Bethesda, United States; 8Georgia Aquarium, Atlanta, United States; 9Department of Infectious Diseases, Emory University School of Medicine, Atlanta, United States Abstract Chondrichthyes (cartilaginous fishes) are fundamental for understanding vertebrate evolution, yet their genomes are understudied. We report long-read sequencing of the whale shark genome to generate the best gapless chondrichthyan genome assembly yet with higher contig contiguity than all other cartilaginous fish genomes, and studied vertebrate genomic evolution of ancestral gene families, immunity, and gigantism. We found a major increase in gene families at the origin of gnathostomes (jawed vertebrates) independent of their genome duplication. We studied vertebrate pathogen recognition receptors (PRRs), which are key in initiating innate immune defense, and found diverse patterns of gene family evolution, demonstrating that adaptive *For correspondence: immunity in gnathostomes did not fully displace germline-encoded PRR innovation. We also
[email protected] discovered a new toll-like receptor (TLR29) and three NOD1 copies in the whale shark.