The brushtail possum is a marsupial native to Australia, where it is a valued and protected species. However, in New Zealand, where it was introduced by European settlers in the 19th century, it is a major pest that threatens native biodiversity and agriculture.
Researchers have now sequenced the entire genetic code of the brushtail possum, which could provide new insights and tools for both conservation and control efforts.
A five-year-long study reveals the secrets of the possum's DNA
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An international team of researchers led by the University of Otago in New Zealand has published the chromosome-level genome assembly of the brushtail possum in Nature Communications.
The lead author of the study, Associate Professor Tim Hore, explained that mapping the genetic code of the possum will benefit those working to both conserve and control the animal.
He said that possums have different roles and statuses in New Zealand and Australia, and their full genetic code is important for both countries as their population management is hindered by the lack of this knowledge.
The researchers found that the possum's genome contains 23 pairs of chromosomes and more than 63,000 genes, slightly larger than that of humans.
They also discovered novel genes that are involved in chemical communication, metabolism, immunity, and imprinting.
Chemical communication genes could be used for population management
One of the most interesting findings of the study was the identification of genes that encode proteins that carry scent molecules in urine.
These molecules are used by possums to communicate with each other, especially during mating.
The researchers found that these genes are switched on in adults, particularly males, but not in newborns.
Hore said that these molecules could be used to manipulate the behaviour and population dynamics of possums.
He suggested that they could be used to lure possums towards a trap or keep them away from pest-free areas.
Since possums are nocturnal, non-visual means of communication are very important for them, according to the researcher.
Professor Dan Tompkins, Science Director at Predator Free 2050 Limited, a co-founder of the study, said that deciphering the possum's genetic code provides an invaluable new knowledge base that enables the exploration of better approaches to control possums in New Zealand.
He said that through the Predator Free 2050 mission, they aim to eradicate possums along with rats and stoats from the whole of New Zealand to protect native biodiversity, and they are always looking for more targeted, efficient, and humane ways of achieving this goal.
Genetic diversity and origin of New Zealand possums revealed
The study also revealed the genetic diversity and origin of New Zealand possums, which were introduced from Australia in multiple waves between 1837 and 1921.
The researchers analyzed nuclear and mitochondrial DNA from more than 200 possums from both countries and found that New Zealand possums are derived from two distinct Australian subspecies that have subsequently hybridized.
The researchers also found evidence of genetic adaptation to different environments in New Zealand, such as colder temperatures and higher altitudes.
They also detected signs of inbreeding and reduced genetic diversity in some populations due to population bottlenecks and isolation.
Hore said that these findings could help track and monitor target populations based on their genes.
Furthermore, they can use genetic markers to identify where possums come from, how they move around, and how they respond to different environmental conditions.
He also said that this information can help them design more effective strategies to reduce their impact on native ecosystems.
Implications for marsupial biology and evolution
The study also has implications for understanding marsupial biology and evolution. Marsupials are a group of mammals that give birth to altricial young that complete their development in a pouch.
The researchers found that possums undergo major physiological changes after birth and at weaning, such as activation of chemosensory and metabolic genes.
The researchers also discovered four genes with imprinted expression not yet detected in other species. Imprinting is a phenomenon where only one copy of a gene is expressed depending on its parental origin.
Imprinting is important for regulating growth and development, especially in the placenta. The researchers found that imprinting is reprogrammed in possums after birth, similar to eutherian mammals (such as humans), but not monotremes (such as platypuses).
Hore said that this work contributes to understanding the evolution of novel mammalian traits, and that marsupials are often used as a model for comparative evolutionary studies because they diverged from other mammals about 160 million years ago.
He said that by comparing the possum's genome with other mammals, they can learn more about how genes and epigenetic mechanisms have evolved and diversified.
