Koalas from a population north of the Brisbane River have evolved a unique genomic immunity to the killer retrovirus threatening their species.
Researchers from 麻豆区 and UMass Chan Medical School discovered the adaptation, offering hope in the effort to save the beloved but endangered marsupial.
, a virologist with 麻豆区’s Australian Institute of Bioengineering and Nanotechnology, said the team were hopeful that this finding could lead to targeted breeding programs that could reduce rates of chlamydia and other health issues linked to koala retrovirus.
“What we found is that there is a single genetic switch that has been activated in about 30 per cent of the koala population in the Sunshine Coast hinterland, suppressing the retrovirus,” Professor Chappell said.
“This is in contrast to what we found in the population on the Gold Coast, where this adaptation is almost completely absent.”
Koala retrovirus suppresses the koala’s immune system and makes them more vulnerable to other infections like chlamydia that has ravaged populations in Queensland and New South Wales.
It has also been
This work, led by , shows that the Sunshine Coast hinterland koalas have developed ‘adaptive genomic immunity’ to the retrovirus in their DNA, similar to how an immune system can adapt after exposure to pathogens.
“Because this ‘genomic immunity’ can be inherited, the discovery suggests koalas with the trait could be used in breeding programs to reduce the susceptibility of other populations to the retrovirus, like on the Gold Coast,” said Dr Blyton.
The researchers were also thrilled to discover the adaptation is apparently spreading through the northern koala population, though evolutionary timescales mean it will take many generations to spread across the entire sub-population on its own.
Professor Chappell said retroviruses can alter the genetic code of a host species, and about 8 per cent of human DNA is from infections over hundreds of millions of years.
“In contrast, the koala retrovirus only entered the marsupial’s genome in the past few thousand years, which is really recent in evolutionary terms.
“Out of all the species on the planet, this is the only one where we can see a genetic response to a retrovirus in real time, rather than looking at responses to things that got into the genome millions of years ago.
"This allows the researchers to study exactly how these iconic critters are responding - it's actually a pretty amazing situation."
At the University of Massachusetts, Professor William Theurkauf had spent decades studying fruit flies and looking at how animals respond to genome invaders from the distant past.
The trans-Pacific collaboration came about when he came across the koala research from 麻豆区 and saw clear parallels and a promising opportunity.
The researchers are quick to caution that while there are many other more acute threats to koalas than the retrovirus, koalas with this adaptive immunity to the retrovirus could provide more resilient animals to repopulate areas where koala numbers have been decimated by disease.
They say the breakthrough has opened the door to new or enhanced breeding programs and more research looking at other positive adaptations in Koalas across Australia, contingent on future funding.
The was published in Cell.
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