The koalas of Australia are not just famous for their cuteness. They have been an unsolved mystery among scientists for their strange eating habits — they enjoy the leaves of eucalyptus that would be toxic or even fatal to most mammals — and their exceptional parental care.
Now an international team of scientists has successfully sequenced the marsupial’s whole genome and answered burning questions about the critter. The study published in Nature Genetics was authored by 54 scientists from seven countries and the whole genome was found to consist of over 26,000 genes.
“The genome provides a springboard for the conservation of this biologically unique species,” said co–lead author Katherine Belov from the University of Sydney in a release.
Researchers found expansions within a particular gene family (P450 gene) and reported that these genes help the koala detoxify the eucalyptus leaves. These genes were found to be expressed in many tissues, especially the liver, indicating its role in detoxification. “.... the koala has evolved an excellent toolkit to deal with eating highly toxic eucalyptus, one made up of lots of copies of the same (or very similar) tools,” explained Dr. Will Nash, one of the authors from Earlham Institute, UK, in the release.
Milk proteins
Researchers also found novel lactation proteins in the koala bears. They reported that these proteins protect the young ones in the pouch and help it develop a strong immune system. “We characterised the main components of the mothers’ milk – which is crucial for koala joeys — born the size of a jellybean and weighing half of one gram,” said Dr. Belov. “We identified genes that allow the koala to fine-tune milk protein composition across the stages of lactation, to meet the changing needs of their young.”
Koala bears are born after just 34-36 days of gestation without an immune system and spend almost six months developing in the pouch. “It also appears these proteins may have an antimicrobial role, showing activity against a range of bacterial and fungal species, including Chlamydia pecorum, the strain known to cause ocular and reproductive disease in koalas,” Dr. Belov added.
The koala bear has a highly specific diet and habitat loss and clearing of native vegetation has brought down its population. “Our next efforts must be in the application of these findings to genetically manage koala populations, advance the treatment of the diseases affecting koalas, with the goal of conserving this very important species,” said Prof. Rebecca Johnson, lead author of the study from the University of Sydney.
