RNA/RNA interactions involved in the regulation of Benyviridae viral cycle

Multipartite viruses possess two or more genomic segments packaged into independent particles. Such group of viruses infect mostly plants, displaying a wide range of genome types: circular ssDNA, dsRNA or ssRNA with both positive and negative polarity. The condition to assure the complete set of genomic segments in each infected cell implies a high level of multiplicity of infection that results in an unsustainable biological cost in terms of viral replication. Beet necrotic yellow vein virus (BNYVV) has been chosen as a model to investigate the aspect of genome integrity of multipartite RNA viruses since it possess the higher number of genomic segments (RNA1 to 5) within ssRNA(+) viruses. In the proposed model, to minimize the cost of the genome integrity preservation, a network of RNA/RNA interactions determines the recognition and mobilization of each genomic RNA in a modular RNP complex that must be considerate as the mobile infectious unit of the multipartite virus during spreading in the plant. If such RNP complex exists as a regulated and functional viral entity, then it’s expected its preservation within tissues and plant species. Aim of this thesis is to experimentally determine the existence of RNA/RNA interactions between genomic BNYVV RNAs and their implication in the viral cycle. In parallel approaches, I have demonstrated that all BNYVV genomic segments are present within the single infected cell in systemic tissues where they accumulate to reach a set point genomic formula that diverges in different types of organ and host (chapter 1 and 2). In a model where vRNAs interact each other to form mobile infective units, RNA-1 and RNA-2 interact at least in silico and in vitro and the rationale for such interaction has been provided in vivo using BNYVV and Beet soil born mosaic virus chimeras.