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. 2019 Aug;3(8):1241-1252.
doi: 10.1038/s41559-019-0945-8. Epub 2019 Jul 29.

Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards

Abigail L Lind  1 , Yvonne Y Y Lai  2 , Yulia Mostovoy  2 , Alisha K Holloway  1 , Alessio Iannucci  3 , Angel C Y Mak  2 , Marco Fondi  3 , Valerio Orlandini  3 , Walter L Eckalbar  4 , Massimo Milan  5 , Michail Rovatsos  6   7 , Ilya G Kichigin  8 , Alex I Makunin  8 , Martina Johnson Pokorná  6   7 , Marie Altmanová  6   7 , Vladimir A Trifonov  8 , Elio Schijlen  9 , Lukáš Kratochvíl  6 , Renato Fani  3 , Petr Velenský  10 , Ivan Rehák  10 , Tomaso Patarnello  5 , Tim S Jessop  11 , James W Hicks  12 , Oliver A Ryder  13 , Joseph R Mendelson 3rd  14   15 , Claudio Ciofi  3 , Pui-Yan Kwok  2   4   16 , Katherine S Pollard  17   18   19   20   21 , Benoit G Bruneau  22   23   24
Affiliations

Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards

Abigail L Lind et al. Nat Ecol Evol. 2019 Aug.

Abstract

Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. Here, we sequence the genome of the Komodo dragon Varanus komodoensis, the largest extant monitor lizard, and generate a high-resolution de novo chromosome-assigned genome assembly for V. komodoensis using a hybrid approach of long-range sequencing and single-molecule optical mapping. Comparing the genome of V. komodoensis with those of related species, we find evidence of positive selection in pathways related to energy metabolism, cardiovascular homoeostasis, and haemostasis. We also show species-specific expansions of a chemoreceptor gene family related to pheromone and kairomone sensing in V. komodoensis and other lizard lineages. Together, these evolutionary signatures of adaptation reveal the genetic underpinnings of the unique Komodo dragon sensory and cardiovascular systems, and suggest that selective pressure altered haemostasis genes to help Komodo dragons evade the anticoagulant effects of their own saliva. The Komodo dragon genome is an important resource for understanding the biology of monitor lizards and reptiles worldwide.

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Conflict of interest statement

Competing Interests: The authors have no competing interests to declare

Figures

Figure 1.
Figure 1.. Estimated species phylogeny of 15 non-avian reptile species, 3 avian species, and 4 mammals.
Maximum likelihood phylogeny constructed from 1,394 one-to-one orthologous proteins. Support values from 10,000 bootstrap replicates are shown. All silhouettes obtained from PhyloPic.org. Photograph of Slasher, a Komodo dragon sampled for DNA in this study. Photo courtesy of Adam K Thompson/Zoo Atlanta, with permission.
Figure 2.
Figure 2.. Type 2 vomeronasal receptors have expanded in Komodo dragons and several other squamate reptiles.
(A) Type 2 vomeronasal gene counts in squamate reptiles. (B) Unrooted gene phylogeny of 1,024 vomeronasal Type 2 receptor transmembrane domains across squamate reptiles. The topology of the tree supports a gene expansion ancestral to squamates (i.e., clades containing representatives from all species) as well as multiple species-specific expansions through gene duplication events (i.e., clades containing multiple genes from one species). Branches with bootstrap support less than 60 are collapsed. Colors correspond to species in (A). Clades containing genes from a single species are collapsed.
Figure 3.
Figure 3.. Gene clusters of Type 2 vomeronasal receptors evolved through gene duplication.
(A) Cluster of 13 vomeronasal Type 2 receptor genes in the Komodo dragon genome. Pink genes are V2R genes and gray genes are non-V2R genes. Gene labels correspond to labels in (B). (B) Unrooted phylogeny of 129 vomeronasal Type 2 receptor genes in Komodo dragon. As most of the genes in this gene cluster group together in a gene phylogeny of all Komodo dragon V2R genes, it is likely that this cluster evolved through gene duplication events. Branches with bootstrap support less than 80 are collapsed. Clades without genes in this V2R gene cluster are collapsed. Genes in the V2R cluster are colored pink and labeled as in (A).
Figure 4.
Figure 4.. Positive selection of mitochondrial genes in the Komodo dragon.
Genes in the Komodo dragon genome under positive selection include components of the electron transport chain, regulators of mtDNA transcription, regulators of mitochondrial translation, and fatty acid beta-oxidation.
See this image and copyright information in PMC

Comment in

  • Decoding dragon DNA.
    Clyde D. Clyde D. Nat Rev Genet. 2019 Oct;20(10):564-565. doi: 10.1038/s41576-019-0168-5. Nat Rev Genet. 2019. PMID: 31388141 No abstract available.

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