Detalle de: Interfamilial recombination between viruses led to acquisition of a novel translation‐enhancing RNA element that allows resistance breaking

Summary Many plant viruses depend on functional RNA elements, called 3′‐ UTR cap‐independent translation enhancers (3′‐ CITE s), for translation of their RNA s. In this manuscript we provide direct proof for the existing hypothesis that 3′‐ CITE s are modular and transferable by recombination in nature, and that this is associated with an advantage for the created virus. By characterizing a newly identified M elon necrotic spot virus ( MNSV ; T ombusviridae ) isolate, which is able to overcome eukaryotic translation initiation factor 4 E ( eIF 4 E )‐mediated resistance, we found that it contains a 55 nucleotide insertion in its 3′‐ UTR . We provide strong evidence that this insertion was acquired by interfamilial recombination with the 3′‐ UTR of an A siatic C ucurbit aphid‐borne yellows virus ( CABYV ; L uteoviridae ). By constructing chimeric viruses, we showed that this recombined sequence is responsible for resistance breaking. Analysis of the translational efficiency of reporter constructs showed that this sequence functions as a novel 3′‐ CITE in both resistant and susceptible plants, being essential for translation control in resistant plants. In conclusion, we showed that a recombination event between two clearly identified viruses from different families led to the transfer of exactly the sequence corresponding to a functional RNA element, giving rise to a new isolate with the capacity to infect an otherwise nonsusceptible host.