The dynamic evolution of Drosophila innubila Nudivirus

Viruses coevolve with their hosts to overcome host resistance and gain the upper hand in the evolutionary arms race. Drosophila innubila nudivirus (DiNV) is a double stranded DNA virus, closely related to Oryctes rhinoceros nudivirus (OrNV) and Kallithea virus. DiNV is the first DNA virus found to naturally infect Drosophila and therefore has the potential to be developed as a model for DNA virus immune defense and host/virus coevolution within its well-studied host system. Here we sequence and annotate the genome of DiNV and identify signatures of adaptation, revealing clues for genes involved in host-parasite coevolution. The circular genome is 155,555 bp and contains 107 coding open reading frames (ORFs) and a wealth of AT-rich simple sequence repeats. While synteny is highly conserved between DiNV and Kallithea virus, it drops off rapidly as sequences become more divergent, consistent with rampant rearrangements across nudiviruses. Overall, we show that evolution of DiNV is likely due to adaptation of a very few genes coupled with high gene turnover.