An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

Abstract

Recombination in RNA viruses is considered to play a major role as a driving force in virus variability to counterbalance loss in fitness that can be due to the accumulation of detrimental mutations. Studies on mixed infections are pertinent for understanding the role of recombination in virus evolution. They also provide important baseline information for studying the biosafety of plants expressing viral sequences. To investigate the possibility of RNA recombination occurrence between two sobemoviruses under little or no selection pressure, we co-infected test plants with Cocksfoot mottle virus (CfMV) and Ryegrass mottle virus (RGMoV). CfMV and RGMoV were selected because of their overlapping host range and geographical distribution. First, symptom development of both viruses in barley (Hordeum vulgare) and oat (Avena sativa) was examined. Both viruses generated quite strong infection symptoms in oat, but synergism was not detected. RGMoV was lethal for barley, whereas CfMV infection in barley was nearly symptomless. RT-PCR analysis revealed 100% infection with both viruses in oat but not in barley. Therefore, an RNA recombination study of CfMV and RGMoV was performed in oat. 105 plants were co-inoculated with both viruses and putative recombinational hot spot regions were screened for recombination events by RT-PCR analysis at a sensitivity level down to 0.1-100 pg of viral genomic RNA. No recombination events between the two sobemoviruses were detected.

No recombination detected in artificial potyvirus mixed infections and between potyvirus derived transgenes and heterologous challenging potyviruses

“…Even if recombination is considered to be frequent within potyvirus populations (Bousalem et al, 2003;Moreno et al, 2004;Revers et al, 1996), our data indicate that recombination between different potyviruses is a rather uncommon event. A similar observation has been made by Meier and Truve (2006), who did not detect any recombinants in oat plants doubleinfected by two sobemoviruses (Cocksfoot mottle virus and Ryegrass mottle virus). This may arise from the absence of certain recombination enhancing sequence motifs neighboring identical regions in Brome mosaic virus that have been reported by Bujarski and Nagy (1996).…”

Overview on Sobemoviruses and a Proposal for the Creation of the Family Sobemoviridae

“…The phylogenetic studies conclude that sobemovirus species have evolved in the absence of interspecies recombination events [ 217 , 231 ]. Also, no recombination event was detected between CfMV and RGMoV under little or no selection pressure in experimentally co-infected plants [ 232 ]. Few intraspecies recombination events have been identified for RYMV after sequencing a large pool of RYMV isolates collected throughout Africa [ 233 , 234 ].…”

Diversification of Rice Yellow Mottle Virus and Related Viruses Spans the History of Agriculture from the Neolithic to the Present

“…The coat protein gene (ORF4) is expressed by a sub-genomic RNA at the 3′ end of the genome. No evidence of recombination between sobemoviruses has been found either in phylogenetic [21] , [56] or experimental studies [22] .…”