Abstract
BackgroundPHYVV and PepGMV are plant viruses reported in Mexico and Southern US as causal agents of an important pepper disease known as "rizado amarillo". Mixed infections with PHYVV and PepGMV have been reported in several hosts over a wide geographic area. Previous work suggested that these viruses might interact at the replication and/or movement level in a complex manner. The aim of present report was to study some aspects of a synergistic interaction between PHYVV and PepGMV in pepper plants. These include analyses of symptom severity, viral DNA concentration and tissue localization of both viruses in single and mixed infections.ResultsMixed infections with PepGMV and PHYVV induced symptoms more severe than those observed in single viral infections. Whereas plants infected with either virus (single infection) presented a remission stage with a corresponding decrease in viral DNA levels, double-infected plants did not present symptom remission and both viral DNA concentrations dramatically increased. In situ hybridization experiments revealed that both viruses are restricted to the vascular tissue. Interestingly, the amount of viral DNA detected was higher in plants inoculated with PepGMV than that observed in PHYVV-infected plants. During mixed infections, the location of both viruses remained similar to the one observed in single infections, although the number of infected cells increases. Infections with the tripartite mixture PHYVV (A+B) + PepGMV A produced a similar synergistic infection to the one observed after inoculation with both full viruses. On the contrary, tripartite mixture PepGMV (A+B) + PHYVV A did not produce a synergistic interaction. In an attempt to study the contribution of individual genes to the synergism, several mutants of PHYVV or PepGMV were inoculated in combination with the corresponding wild type, second virus (wt PepGMV or wt PHYVV). All combinations tested resulted in synergistic infections, with exception of the TrAP mutant of PepGMV (PepGMV TrAP-) + PHYVV.ConclusionIn this report, we have demonstrated that synergistic interaction between PHYVV and PepGMV during a mixed infection is mainly due to an increased DNA concentration of both viruses, without any noticeable effect on the localization of either virus on infected plant tissue. Our results have shown that the viral component A from PepGMV is important for synergism during PHYVV-PepGMV mixed infections.
Highlights
Pepper huasteco yellow vein virus (PHYVV) and Pepper golden mosaic virus (PepGMV) are plant viruses reported in Mexico and Southern US as causal agents of an important pepper disease known as “rizado amarillo”
Plants inoculated with the mixture PepGMV and PHYVV show more severe symptoms than those observed in either single infection (Figure 1B)
In plants inoculated with this tripartite mixture, only the replicative forms of PepGMV were detected in systemic tissue (Figure 6D; Table 1). These results indicate that the combination of PepGMV A and PHYVV is sufficient for the establishment of a viral synergistic interaction in pepper plants
Summary
PHYVV and PepGMV are plant viruses reported in Mexico and Southern US as causal agents of an important pepper disease known as “rizado amarillo”. The aim of present report was to study some aspects of a synergistic interaction between PHYVV and PepGMV in pepper plants. These include analyses of symptom severity, viral DNA concentration and tissue localization of both viruses in single and mixed infections. Geminiviruses are plant viruses that have a wide host range They possess a circular, single-stranded DNA (ssDNA) genome packaged into isometric twinned particles. Pepper huasteco yellow vein virus (PHYVV) and Pepper golden mosaic virus (PepGMV) are members of the genus Begomovirus. The genomes of these whiteflytransmitted viruses are organized into two circular ssDNA components, DNAs A and B (Figure 1A). Several reports have demonstrated that mixed infections with PHYVV and PepGMV are common in those crops and, in many cases, this complex has become the predominant mixture [2,4,5,6,7,8]
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