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Biting on eucalyptus leaves would kill most other mammals, but koalas have a large number of genes that allow them to tolerate their toxic diet.
However, the same genes also play a role in the manufacture of drugs used to treat sick or injured animals.
This double-edged sword is only one of the discoveries of 39, an Australian project that sequenced the entire genome of the koala.According to Rebecca Johnson, of the Australian Museum Research Institute [1965-19005] "the genetic model is on par with the human genome." "We have found more than 26,000 genes, "said Professor Johnson, who co-led an international consortium." We have sequenced and assembled the entire koala genome … 3.5 billion base pairs, which is actually a little larger than the human genome. "
The genome gives an overview of koalas highly specialized diet, imm A system, biodiversity and evolution, Professor Johnson and his colleagues report in the journal Nature Genetics .
They said that the information would guide the conservation of the iconic animal, which is vulnerable to habitat loss,
"It is such an important animal for our country, it's an important ambassador to understand why habitat needs to be protected, "said Professor Johnson
. 19659005] In the few hours a day, they are not asleep in the hollow of a tree, they eat their way through about 600-800 grams of leaves.
But no leaves. They graze only about 20 of the 900 known species of eucalyptus.
They also rely almost exclusively on leaves for water, looking for leaves containing at least 50% water, Professor Johnson said. allow koalas to eat eucalyptus leaves. "/>
The detoxification genes allow koalas to eat eucalyptus leaves.
Photo: 123RF
"Understanding how koalas choose their trees and why they choose their trees at the molecular level is bound to make sure that they have something to eat and live on ", did she say. genome shows that koalas have many bitter taste receptors, as well as a duplication of what is called a "taste of water" gene.
"This could be … a way to feel the water in the trees" Johnson says
They also have a large number of genes that produce enzymes that detoxify terpenes and phenolic compounds.
"Everything must be detoxified [genes] but koalas seem to have them in greater quantity".
But there is a disadvantage for this family of genes, known as cytochrome P450 monooxygenase or CYP 450.
The same enzymes that detoxify substances in the leaves also rapidly break down anti-inflammatory analgesics
So by giving [koalas] pain relief that uses these pathways "Enzymes also act on the metabolism of antibiotics," says Peter Timms, of the Sunshine Coast University, who also participated in the 39, study
. that we can give them. Then, as we give them higher doses, we then disrupt their bacteria from the intestinal flora, "says Professor Timms
Antibiotics are used to treat chlamydia, a bacterial disease that can cause blindness, infertility, and urinary tract infections. Joeys can gain some protection against breast milk disease.
The team identified a number of genes involved in fine milk processing, including proteins that may have antimicrobial properties.
The challenge of treating koalas
Chlamydia affects all koala populations, said Professor Timms, whose team is working on a vaccine against infectious disease and koala retrovirus
Retrovirus, which has been associated with cancer, appears to aggravate chlamydia. [19659005"InrealitytheymovetothepeopleofJapan"saidtheteacherTimms
"The southern koalas are not yet infected, while the northern koalas are."
The treatment of these diseases was difficult because little was known about the immune system of the animal
"[The koala genome is] revolutionizing both what we can understand but also what we can do, "said Professor Timms
. Advanced technology has not only identified all families of immune genes and their functions, but it has also helped to better understand how the retrovirus has colonized the animal's DNA.
"For the first time, we were able to see how many times" It's not quite equal, there are different strains in there. "
He said that the level of detail would allow them to identify which strains are more dangerous. they can modify tests and vaccines to target the virus.
"We could not do it before because we did not know what to look for."
The genome will help Professor Timms and his team monitor how different animals respond to vaccines.
"Now we have what I did The project, which lasted five years, is based on samples taken from three koalas: Pacific Chocolate and Bilbo, two female koalas that succumbed to the disease, chlamydia; man called Birke, who was bothered by a dog
"These are pretty emotional moments when you sit down and look at an animal that is autopsied (examined after death)," said Professor Johnson
. we do what we do. "
The genetic information of koalas, which were from northern New South Wales and southern Queensland, provided insights into the diversity of populations around the area. 39; Australia. The population of Queensland and New South Wales has been relatively high and that of South Australia and South Australia is much less diversified, "said Professor Johnson
. Conservation measures are quite urgent in this case because it is the people who have all the diversity, she said.
The main threats to diversity include habitat fragmentation caused by clearing and urbanization.
"If you do not have diversity, you increase the chances of inbreeding and many genetic diseases can occur from a very low population diversity," he said. said Professor Johnson
. "Researchers around the world can now use it to study the unique features or characteristics of the koala genome, or they can use it for comparative genomics," said Professor Johnson
. "It's only the fourth marsupial to be sequenced – and we have a lot of marsupials in Australia."
