The entire genome of the white shark has now been decoded in detail. The white shark genome was also compared to gthe genomes of other vertebrates including the giant whale shark and humans.
The white shark has a genome that is one and half time larger than the human genome.
Very large-bodied animals do not get cancer more often than humans. They have evolved superior cancer-protective abilities. The genetic innovations discovered in genome stability genes in the white and whale shark could be adaptations facilitating the evolution of their large bodies and long lifespans.
The genome is revealing evolutionary adaptations in genes linked to wound healing pathways. Sharks are known for their impressively rapid wound healing.
PNAS – White shark genome reveals ancient elasmobranch adaptations associated with wound healing and the maintenance of genome stability
Sharks represent an ancient vertebrate lineage whose genomes have been only minimally investigated. We here characterize the genome of the white shark, an apex marine predator. Its genome is 4.63 Gbp, over half of which is represented by repeat sequences, including a large proportion of transposable elements. Comparative analysis of white shark, whale shark, chimaera, and several nonchondrichthyan vertebrate genomes reveals positive selection and enrichment of gene functional categories and pathways involved in wound healing, and in the maintenance of genome stability in sharks. Sharks show a limited repertoire of olfactory genes but an expanded vomeronasal (VR2) gene family, suggesting an alternative mechanism underlying their vaunted sense of smell.
The white shark (Carcharodon carcharias; Chondrichthyes, Elasmobranchii) is one of the most publicly recognized marine animals. Here we report the genome sequence of the white shark and comparative evolutionary genomic analyses to the chondrichthyans, whale shark (Elasmobranchii) and elephant shark (Holocephali), as well as various vertebrates. The 4.63-Gbp white shark genome contains 24,520 predicted genes, and has a repeat content of 58.5%. We provide evidence for a history of positive selection and gene-content enrichments regarding important genome stability-related genes and functional categories, particularly so for the two elasmobranchs. We hypothesize that the molecular adaptive emphasis on genome stability in white and whale sharks may reflect the combined selective pressure of large genome sizes, high repeat content, high long-interspersed element retrotransposon representation, large body size, and long lifespans, represented across these two species. Molecular adaptation for wound healing was also evident, with positive selection in key genes involved in the wound-healing process, as well as Gene Ontology enrichments in fundamental wound-healing pathways. Sharks, particularly apex predators such as the white shark, are believed to have an acute sense of smell. However, we found very few olfactory receptor genes, very few trace amine-associated receptors, and extremely low numbers of G protein-coupled receptors. We did, however, identify 13 copies of vomeronasal type 2 (V2R) genes in white shark and 10 in whale shark; this, combined with the over 30 V2Rs reported previously for elephant shark, suggests this gene family may underlie the keen odorant reception of chondrichthyans.
SOURCES- PNAS, Nova Southeastern University
Written By Brian Wang
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