Defence mechanisms against Koala retroviruses

Long Terminal Repeat retroelements are relics of retrovirus infection in the history of eukaryotic evolution. In the present day, most of LTR elements have lost parts of their genome so that they are no longer infectious. Rare exceptions include the gypsy family of retrotransposons present in Drosophila genome, which produce viron-like particles in somatic cells to infect the germline. It is known that a class of small RNA called Piwi-interacting RNA (piRNA) is the primary guardian for gypsy retrotransposons in the soma as well as for other transposons in the germline. However, little is known about how retroviruses infect vertebrate germline cells and what the potential defence mechanism outside the germline is.

Koala genome project revealed that Koalas carry a class of retroviruses called Koala retrovirus (KoRV) that transmit between individuals as well as across the generation, indicating that KoRV infects germline cells even today. The project aims to uncover the defence mechanism against KoRV particularly in the gonadal tissues, which involves Koala tissue sampling across Australia, RNA sequencing and the accompanying computational analysis.