French biologists from the National Center for Scientific Research (Paris) found that giant viruses related to the genus pandoravirus (Pandoravirus) are able to create new genes from scratch, which is considered a rare and unlikely evolutionary phenomenon. The article of scientists is published in the journal Nature Communication.
Pandoraviruses infecting amoeba Acanthamoeba castellanii, were discovered in 2013 and at that time were the most giant viruses. By 2018 the genus included only three species – Pandoravirus salinus, Pandoravirus dulcis and Pandoravirus inopinatum. The first species was isolated from shallow sediments in Chile, the second from mud from the bottom of the pond in Australia, and the third from a patient with amoebic keratitis in Germany. However, in a new paper, a team of scientists described three more strains of pandoraviruses: Pandoravirus quercus, isolated from soil in France, Pandoravirus neocaledonia from mangrove swamps in New Caledonia (Pacific) and Pandoravirus macleodensis from a freshwater pond in Australia.
The researchers analyzed and compared genomes, transcripts (a set of DNA transcripts) and protein composition in all six pandoravirus species. It turned out that 82-87 percent of the genome underwent a transcription process (RNA synthesis on the DNA matrix), but only 62-68 percent carried information on the structure of proteins, that is, they were coding.
The results of the analysis also showed that genes specific for clades (groups having a common ancestor of organisms) and strains had similarities with both non-coding intergenic gaps and with the universal genome, that is, the set of genes that each strain possesses.
This is due to the fact that these genes randomly emerged from non-coding regions, but under the influence of natural selection they became similar to genes that are characteristic of the whole family of viruses. Such an evolutionary scenario, according to which new coding genes can appear from scratch, and not be copied or transferred from other organisms, has long been considered statistically unlikely, but recently it is confirmed by the results of studies of the yeast genomes, fruit flies, Tal’s reticular species, mammals, including primates