Recombination and pseudorecombination driving the evolution of the begomoviruses Tomato severe rugose virus (ToSRV) and Tomato rugose mosaic virus (ToRMV): two recombinant DNA-A components sharing the same DNA-B

Abstract

BackgroundBegomoviruses are dicot-infecting, whitefly-transmitted viruses with a genome comprised of one or two molecules of circular, single-stranded DNA. In Brazil, tomato-infecting begomoviruses have emerged as serious pathogens since the introduction of a new biotype of the insect vector in the mid-1990’s. Tomato rugose mosaic virus (ToRMV) and Tomato severe rugose virus (ToSRV) are often found in tomato fields. The complete sequence of the DNA-B components of ToSRV and ToRMV show an identity of 98.2%. Additionally, the high nucleotide identity (96.2%) between their common regions indicates that these two viruses may share the same DNA-B.MethodsTomato seedlings were biolistically inoculated with ToSRV (DNA-A and DNA-B) and ToRMV (DNA-A and DNA-B) infectious clones in every possible combination of single or mixed infection. Symptom expression was evaluated for up to 35 days post-inoculation (dpi). DNA was extracted at 28 dpi and the presence of each viral genomic component was examined by rolling circle amplification (RCA) followed by digestion, as well as by quantitative, real-time PCR. Sequence comparisons, recombination and phylogenetic analyzes were performed using EMBOSS needle, RDP program and maximum likelihood inference, respectively.ResultsSymptoms in tomato plants inoculated with the different combinations of ToRMV and ToSRV DNA-A and DNA-B components consisted of a typical mosaic in all combinations. Pseudorecombinants were formed in all possible combinations. When two DNA-A or two DNA-B components were inoculated simultaneously, the ToRMV components were detected preferentially in relation to the ToSRV components. The combination of minor changes in both the Rep protein and the CR may be involved in the preferential replication of ToRMV components. Recombination and phylogenetic analyzes support the exchange of genetic material between ToRMV and ToSRV.ConclusionsToRMV and ToSRV form viable pseudorecombinants in their natural host (Solanum lycopersicum) and share the same DNA-B. ToRMV DNA components are preferentially replicated over ToSRV components. These results indicate that the emergence of ToRMV involved both recombination and pseudorecombination, further highlighting the importance of these mechanisms in the emergence and adaptation of begomoviruses.

Vector-Enabled Metagenomic (VEM) Surveys Using Whiteflies (Aleyrodidae) Reveal Novel Begomovirus Species in the New and OldWorlds

“…The high genetic diversity observed in begomoviruses may be explained by their high nucleotide substitution rates which approximate those of RNA viruses [ 15 , 16 ], mechanistic predispositions to recombination processes [ 17 , 18 , 19 ], and ability to acquire extra DNA components such as satellites [ 12 , 20 , 21 ]. Recombination processes in particular appear to be a major contributor to begomovirus genetic diversity and adaptability [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] and include reassortment of DNA-A, DNA-B, and satellite molecules ( i.e. , pseudo-recombination), as well as recombination during replication.…”

Biological characterization of Tomato leaf curl New Delhi virus from Spain

“…This virus has spread quickly, probably due to the expansion of monocultures susceptible to virus transmitted by B. tabaci (tomato, melon, watermelon, zucchini squash) and overlapping growing seasons, especially in summer where the high temperatures favour the occurrence of high populations of B. tabaci (EFSA Panel on Plant Health (PLH), 2013). On the other hand, disease management programmes for this virus need to be prepared for possible recombination events between ToLCNDV and monopartite begomoviruses in tomato, or the appearance of betasatellites which are reported to have significant epidemiological consequences (Silva et al, 2014).…”

Infectivity of Deinbollia mosaic virus, a novel weed-infecting begomovirus in East Africa

“…Within the B. tabaci complex, the Middle East-Asia Minor 1 cryptic species (MEAM1, formerly B biotype) has been reported to colonize plants belonging to diverse botanical families and may be responsible for the horizontal transfer of begomoviruses between crop and weed plants [ 9 , 10 ]. Weed-infecting begomoviruses act as progenitors of crop-infecting begomoviruses and contribute to their diversity via genetic recombination [ 11 , 12 ]. Despite the important role these weed-infecting begomoviruses play in crop diseases, they remain insufficiently studied in Africa.…”