An article published in the journal “Nature Ecology & Evolution” reports a complete genome sequencing of the Komodo dragon, the largest lizard existing today. A collaboration between the Gladstone Institutes, the University of California, San Francisco and the Atlanta Zoo that includes researchers from the Universities of Florence and Padua, Italy, led to the sequencing of the DNA of the species classified as Varanus komodoensis using various technologies to obtain a high quality result. This made it possible to compare that genome with that of other reptiles to understand how it has become a lethal predator with unique physiological and metabolic characteristics among reptiles.
The Komodo dragon lives in various Indonesian islands even if the name refers only to that of Komodo. A length that can exceed 3 meters, a weight that even in nature can exceed 80 kg, a metabolism that can accelerate to levels similar to those of mammals despite being a cold-blood animal, the ability to smell its prey from more than 10 km away and the saliva that contains an anticoagulant that makes its bite even deadlier make it a top predator in the ecosystems in which it lives. Part of the monitor lizard (Varanidae) family, this species may have emerged in Australia almost 4 million years ago and then spread to the current Indonesian islands due to low sea levels during the last glacial period.
Despite these extraordinary qualities of the Komodo dragon, so far little was known about the genetic characteristics at their origin. Benoit Bruneau, one of the lead authors of this research, explained that 9 years ago a project was started to understand how genomes evolve and at that time other teams of researchers had already sequenced those of turtles, snakes and birds while that of crocodiles was in the process of sequencing but the varanid family this species belongs to was missing.
For this research the genomes of two specimens of Komodo dragon from the Atlanta zoo called Slasher and Rinca were sequenced. Katherine Pollard, the other lead author of this research, explained that the problem in this type of research is that vertebrate genomes are large and contain many repetitive sequences. Most sequencing technologies produce only short fragments of sequences at a time and when they contain repetitive elements it’s impossible to tell which part of the DNA they belong to and which other parts they’re connected to. For this reason, the researchers used multiple technologies that include broad-spectrum sequencing and physical mapping to assemble the pieces.
The long task brought the desired results. The researchers identified the parts of the Komodo dragon’s DNA at the origin of characteristics such as aerobic resistance, other peculiarities of metabolism and physiology and the many genes that encode some receptors of the vomeronasal organs linked to this animal’s smell. The comparison with the DNA of other reptiles helped to understand the Komodo dragon’s specific characteristics and its evolution.
Even a predator like the Komodo dragon got threatened by human activities that reduced its habitat and today it’s a protected species in Indonesia. The study of its DNA will also help to find the best strategies to enable its survival.
