Nucleo cytoplasmic large DNA virus (NCLDV) superfamily forms a diverse group of viruses that infects a wide range of eukaryotic hosts (e.g. vertebrates, insects, protests, etc.). These viruses are characterized by a huge range in genome size (between 100kb and 1.2Mb), coupled with an extraordinary diverse genomic repertoire. Here I will review some recent results that shed light on the origin and genome evolution of these viruses, introducing the idea that these viruses evolved using a complex process of genomic accordion that imply successive steps of genome expansions (duplication and gene transfers) and genome reduction, in addition to movement and amplification of diverse mobile genetic elements.
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