The nematode genome provides an understanding of the evolution of parasites

Scientists from the Max Planck Institute for Development Biology, along with US colleagues, have deciphered the genome of the Pristionchus pacificus nematode, thereby bringing new insights into the evolution of parasites.

In their study, published recently in Nature Genetics, scientists from the research department of Professor Ralf J. Sommer in Tübingen, Germany show that the genome of the nematode contains a large number of genes, in some have unexpected functions.

Some genes help break down harmful substances and help animals survive in unusual habitats: Pristionchus uses beetles as a shelter and a means of transport; they parasitize on some fungi and bacteria that grow on the beetles' bodies. This provides a clue to understanding the complex interaction between host and parasite species.

With over a million different species, nematodes are the largest group of organisms in the animal kingdom. Worms with a common length of about 1 mm are found on all continents and ecosystems on Earth. Some are the main pathogens in humans, animals and plants. In the group of nematodes, at least 7 parasitic forms are independently developed. In fact, a member of the nematode group became famous: because of its modest lifestyle, small size and rapid reproduction, Caenorhabditis elegans is one of the most commonly used species in biological laboratories. . It was also the first multicellular species whose genome was completely decoded in 1998.

Scientists have deciphered the genome of the Pristionchus pacificus nematode, thus gaining a new understanding of the evolution of this parasite.(Photo: Max Planck Development Biology Institute).

10 years later, a group of scientists from the Max Planck Institute for Biological Development in Tübingen (Germany), together with researchers from the National Institute of Genome Studies at St. Louis (USA), published the genome of another roundworm, Pristionchus pacificus. Pristionchus has a very special habitat : they live together with skin bugs, dung beetles and potato beetles in order to parasitize bacteria and fungi that grow on the bodies of these beetles after they die. Worms use beetles as mobile habitats that provide hiding places and food for them.

When moving from land to beetles, the habitat of the nematode changes rapidly. Worms must protect themselves from the toxins on the host. The method they used to cope with the living conditions on the beetle body has long attracted attention, because this form of life can be seen as a preparation for the subsequent parasite process. At least that's what the researchers are skeptical of.

Pristionchus pacificus' gene sequence has confirmed that skepticism: the genome, which includes 170 megabases, has more than 23,500 protein-encoded genes. Meanwhile, Caenorhabditis elegans and the human parasite Brugia malayi (genome sequenced in 2007) have only 20,000 and 12,000 protein-coding genes. Ralf Sommer explained: 'This phenomenon in Pristionchus is partly due to gene reproduction, in which some genes can assist in the destruction of harmful substances and help animals survive in complex ecosystems on the body. beetles'.

Surprisingly, Pristionchus possesses some genes that Caenorhabditis elegans does not have, although these genes are found in parasitic plants. Genes coding for cellulases - enzymes necessary to break down cell walls in plants and microorganisms - attract special attention from scientists. Sommer said:

'The really interesting question is still ahead. Using string data, we can analyze how Pristionchus adapted habitats. This will undoubtedly bring new insights into the evolution of parasites'.