Lateral gene transfer, lineage-specific gene expansion and the evolution of Nucleo Cytoplasmic Large DNA viruses

Nucleo Cytoplasmic Large DNA viruses (NCLDVs) are a diverse group that infects a wide range Of eukaryotic hosts (for example, vertebrates, insects, protists, ... ) and also show a huge range in genome size (between 100 kb and 1.2 Mb). Here I review some recent results that shed light on the origin and genome evolution of these Viruses. Current data suggests that NCLDVs could have originated from a simple and ancient viral ancestor with a small Subset of 30-35 genes encoding replication and structural proteins. Subsequent lateral gene transfer of both cellular genes and diverse families of Mobile Genetic Elements, followed by massive lineage-specific gene duplications is probably responsible for the huge diversity of genome size and composition found in extant NCLDVs. (C) 2009 Elsevier Inc. All rights reserved.