BEET NECROTIC YELLOW VEIN VIRUS AND BEET SOILBORNE MOSAIC VIRUS: A PRELIMINARY STUDY OF RNAs REASSORTMENT

Beet necrotic yellow vein virus (BNYVV) and Beet soil-borne mosaic virus (BSBMV) (Benyviridae family) are distinct but closely related species possessing the same host range, vector and multipartite genome of four to five ssRNAs (+) that represent an interesting model to study plant-virus interactions. RNA-1 and -2 combination (helper strain) is essential for the infection and the replication of both viruses, while RNA-3 and -4 are accessory RNAs playing important roles in plant-virus and virusvector interactions, respectively. Previous work demonstrated on the one hand the ability of BNYVV/BSBMV helper strains to handle the replication and packaging of cognate small RNA segments, on the other hand, the availability of a functional exchange of genomic RNA-1 between both viral species. nterestingly, one of the two chimeric combinations induced a strong necrosis of the infected Chenopodium quinoa leading to a dead end for the recombinant virus. Such dramatic cell death or incompatible reaction could explain why no natural chimeras have ever been found in plant naturally infected with both viruses. As both viruses could co-exist in the same plant, a mixture of both genomic RNAs in the same cell should be avoided, particularly when the virus moves at a long distance. The unavailability of benyviridaes genomic RNA reassortment, in particular for RNA-1, has been tested in C. quinoa and Nicotiana benthamiana local and systemic host, respectively, using BNYVV/BSBMV full-length infectious cDNA clones and agroclones in a genetic reverse approach.