Apoptotic arms races in insect-baculovirus coevolution

Baculoviruses, like their holometabolous host insects, comprise a monophyletic clade and, since the evolutionary origin of this virus family, have coevolved with their hosts. Despite this intimate coevolutionary relationship, baculoviruses have occasionally diverged independently of the host phylogeny by acquiring new infection mechanisms. Given that current baculovirus genomes contain various anti-apoptotic genes and pseudogenes, the possibility arises that ancient baculoviruses had the genetic means to counter antiviral host apoptosis mechanisms. In this review, we propose an evolutionary scenario for baculovirus diversification in which the development of novel antiviral apoptosis mechanisms in host insects provided the necessary pressure to produce new baculovirus lineages possessing novel anti-apoptotic genes. This apoptotic arms race and subsequent viral host adaptation likely play a crucial role in the establishment of baculovirus diversity.