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

Abigail Lind ,Lukáš Kratochvíl ,Joseph R Mendelson ,Claudio Ciofi ,Renato Fani ,Elio Schijlen ,Massimo Milan ,Alex Makunin ,Valerio Orlandini ,Katherine S Pollard ,Michail Rovatsos ,Pui Yan Kwok ,Marco Fondi ,Yulia Mostovoy ,Tomaso Patarnello ,James W Hicks ,Alisha K Holloway ,Alessio Iannucci ,Walter L Eckalbar ,Tim S Jessop ,Ilya G Kichigin ,Marie Altmanová ,Angel C Y Mak ,Yvonne Y Y Lai ,Ivan Rehák ,Martina Pokorná ,Oliver A Ryder ,Petr Velenský ,Vladimir A Trifonov ,Benoit G Bruneau

doi:10.1038/s41559-019-0945-8

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.

Highlights

Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals
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
We sequenced the Komodo dragon genome principally from DNA isolated from peripheral blood of two male Komodo dragons housed at Zoo Atlanta: Slasher, offspring of the first Komodo dragons given to US President Reagan from President Suharto of Indonesia, and Rinca, an unrelated juvenile

Summary

Introduction

Monitor lizards are unique among ectothermic reptiles in that they have high aerobic capacity and distinctive cardiovascular physiology resembling that of endothermic mammals. We 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. Varanids have a unique cardiopulmonary physiology and metabolism with numerous parallels to the mammalian cardiovascular system Their cardiac anatomy is characterized by well-developed ventricular septa (‘muscular ridge’ and ‘bulbus lamellae’) resulting in a functionally divided heart[3]. Komodo dragons engage in aggressive intraspecific conflicts over mating, territory and food, and wild individuals often bear scars from previous conflicts[4]

Methods

Results

Conclusion