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How Pacific Chocolate helped scientists crack the koala’s genetic code

How Pacific Chocolate helped scientists crack the koala’s genetic code
02 Jul
11:56

What started as a small collaboration among Australians expanded to include researchers from 29 institutions in seven countries for a complex project likened to cutting up an encyclopaedia, throwing the pieces on the floor and reassembling them in order.

The koala genome is slightly larger than the human genome, with a similar number of genes – 26,558. The research to crack it allowed scientists to develop vaccines to treat the chlamydia that has been causing blindness and sterility and makes koalas leak urine if untreated. Along with land clearing, disease has been a major threat to koala populations.

The original subject for the research on the koala genome: Pacific Chocolate.

The original subject for the research on the koala genome: Pacific Chocolate.

“It’s well-accepted even by the NSW government that population numbers will decline over the next three generations, which is only 20 years,” Professor Johnson said. “The acknowledgement that without doing something they will continue to decline means that we’re in a position to use science to inform policy.”

One discovery of the research was that koalas have “lots of detoxification genes” which lets them live on eucalyptus leaves.

“Basically they’re super detoxers that allow them to eat this highly specialised diet,” Professor Johnson said.

The team’s other joint leader, Professor Kathy Belov from the University of Sydney’s Science Faculty, said the project’s success would allow struggling koala populations to be managed better.

“In southern populations, you’ve got good numbers of koalas,” she said. “But the problem is they lack genetic diversity, which is very troubling because those sort of populations don’t adapt well when there are new threats – new diseases or changes due to climate change, for instance.

“Whereas in the north – in southern Queensland and northern NSW – we have very healthy populations based on their genetics but [they] are now threatened due to urbanisation. Having the genetic data gives us a lot of power to really manage koalas at a fine scale and I think we need to be doing that.”

Professor Belov said a new understanding of how koala milk helps joeys survive when they are born could have applications for humans and other animals.

“We studied the milk of koalas and found over 850 immune genes,” she said. “Some of these genes are completely novel and haven’t been seen before in any other species.”

The first five of these genes to be studied show the potential for peptides that could treat multi-drug-resistant infections including golden staph in hospitals.

“We see opportunities to commercialise some of these peptides for use in humans and animals,” Professor Belov said. “We’ve got a good amount of data now to help develop milk substitutes to feed orphan joeys.”

La Trobe University professor Jenny Graves, who pioneered koala genetics in the 1980s, said the scientific understanding of all marsupials was enhanced by cracking the koala genome.

“It seems to have more genes in it than some of the other marsupials,” she said. “We certainly know there are more copies of genes that are particularly relevant to the koala, like genes that can break down the nasty stuff in gum leaves.”

There were also extra “smell” genes that allowed koalas to detect eucalyptus leaves containing at least 55 per cent water content, which was important because they do not drink.

But Professor Graves said there was one gene missing.

“The koala is the cutest animal on the planet possibly with the exception of pandas,” she said. “So we were always after the ‘cute’ gene. Unfortunately there’s no such thing.”

Garry Maddox

Garry Maddox is a Senior Writer for The Sydney Morning Herald.

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