The rhinoceros belongs to an order of mammals called the odd-toed ungulates which also includes horses and tapirs. They are found in Africa and Asia. Until recently, evidence indicated that throughout their evolutionary history, retroviruses such as murine leukemia virus had not colonized their genomes, unlike most other mammalian orders. The process of colonization is called retroviral endemism and has resulted in most mammalian genomes being composed of up to ten percent of retroviral-like sequences. An analysis of the genomes of modern and extinct rhinos headed by the German Leibniz Institute for Animal and Wildlife Research (Leibniz-IZW) has now found that African rhinos contain dozens of retroviruses in their genomes that are absent from the genomes of Asian rhino species, such as the Sumatran and Javan rhinos, and that rhinos The African black rhinoceros has two associated groups, one missing from the white rhinoceros. The confinement of gammaric retroviruses to African rhinos and the close relationship between the viruses and rodent viruses, particularly those in African rodents, suggests that the African rhinoceros was infected by an exogenous viral species and its genomes are colonized in Africa. The work has been published in the scientific journal Virology Journal.
Retroviruses, such as the adjuvant causative agent, HIV-1, are unique among viruses in that they have to integrate into the host’s DNA as part of their replication cycle. If this occurs in the germline in sperm or egg cells, it can become part of the host’s genome inherited by the next generation and then be present in every cell of the offspring’s body. This evolutionary process has occurred so often that, on average, up to 10 percent of the mammalian genome is made up of retroviruses or their remnants. A previous study of available genomes from horses and their relatives indicated that they, along with rhinos and tapirs, had not been invaded by retroviruses, a group of viruses related to mouse and avian viruses that have successfully colonized most mammalian genomes.
“We had data from several species of rhinos where we kept finding large fragments of gamaritroviruses,” says Dr. Kyriakos Tsangaras, lead author of this research. “When we used a lot of the newer and more complete reference genomes from modern and extinct rhinos, we found that the African rhinoceros Only he is the colonizer.” Stady.
The scientific team, together with colleagues from Australia and Germany, found that two different virus populations colonized African rhinos. One of them had only colonized black rhinos (Diceros bicornis(not a white rhino)Ceratotherum is a toxin) and was evolutionarily smaller than the one shared by both. Because both populations are restricted to African rhinos, the study suggests that the African rhino subspecies has been infected and its genomes are colonized in Africa, which is why gamearitroviruses have not been found in Asian rhinos and other rhino relatives.
“Ultimately this is due to a lack of high-quality wildlife reference sequences,” says Professor Alex Greenwood, Head of Wildlife Diseases at Leibniz-IZW. “While things have improved a lot since the first human genome was sequenced, you miss things like viral history when databases lack a lot of species or high-quality reference genomes from many species. It’s really another example of why we need more genome sequences.” reference from wildlife because we don’t know what else we’re missing and any conclusions to draw about the presence and absence of sequences that might turn out to be a result of a lack of information.”