Viral genome segmentation can result from a trade-off between genetic content and particle stability

The evolutionary benefit of viral genome segmentation is a classical,yet unsolved question in evolutionary biology and rna genetics. theoretical studies anticipated that replication of shorter rna segments could provide a replicative advantage over standard size genomes. however,this question has remained elusive to experimentalists because of the lack of a proper viral model system. here we present a study with a stable segmented bipartite rna virus and its ancestor non-segmented counterpart,in an identical genomic nucleotide sequence context. results of rna replication,protein expression,competition experiments,and inactivation of infectious particles point to a non-replicative trait,the particle stability,as the main driver of fitness gain of segmented genomes. accordingly,measurements of the volume occupation of the genome inside viral capsids indicate that packaging shorter genomes involves a relaxation of the packaging density that is energetically favourable. the empirical observations are used to design a computational model that predicts the existence of a critical multiplicity of infection for domination of segmented over standard types. our experiments suggest that viral segmented genomes may have arisen as a molecular solution for the trade-off between genome length and particle stability. genome segmentation allows maximizing the genetic content without the detrimental effect in stability derived from incresing genome length. © 2011 ojosnegros et al.