The brushtail possum is a protected and treasured species in its native range of Australia, but also a devastating folivore and predator introduced into New Zealand. Like other marsupials, possums give birth to altricial young which undergo most of their development suckling on the teat. Intensive study from a pest-control perspective has meant possums are a model marsupial, yet many aspects of their reproductive biology are unknown.
Here we report the first chromosome-level assembly of the possum genome, and using large cohorts of RNA-sequencing in pouch-young and adults, identified metabolic signatures recording the transition from a milk diet to herbage at weaning.
Nuclear and mitochondrial analysis showed high levels of nucleotide diversity in the New Zealand possum is due to hybridisation between Tasmanian and mainland source populations. This diversity, along with phasing of long-read methylation sensitive sequencing, allowed us to distinguish expressed parental alleles throughout the genome and identify allele-specific methylation. Through this process, we uncovered several possum genes with imprinted, parent-specific expression not yet seen in other species. This result challenges the expectation that marsupial imprinting is restricted to orthologues of imprinted genes in humans and mice.