Large Bottleneck Size in Cauliflower Mosaic Virus Populations during Host Plant Colonization

Abstract

The effective size of populations (Ne) determines whether selection or genetic drift is the predominant force shaping their genetic structure and evolution. Despite their high mutation rate and rapid evolution, this parameter is poorly documented experimentally in viruses, particularly plant viruses. All available studies, however, have demonstrated the existence of huge within-host demographic fluctuations, drastically reducing Ne upon systemic invasion of different organs and tissues. Notably, extreme bottlenecks have been detected at the stage of systemic leaf colonization in all plant viral species investigated so far, sustaining the general idea that some unknown obstacle(s) imposes a barrier on the development of all plant viruses. This idea has important implications, as it appoints genetic drift as a constant major force in plant virus evolution. By co-inoculating several genetic variants of Cauliflower mosaic virus into a large number of replicate host plants, and by monitoring their relative frequency within the viral population over the course of the host systemic infection, only minute stochastic variations were detected. This allowed the estimation of the CaMV Ne during colonization of successive leaves at several hundreds of viral genomes, a value about 100-fold higher than that reported for any other plant virus investigated so far, and indicated the very limited role played by genetic drift during plant systemic infection by this virus. These results suggest that the barriers that generate bottlenecks in some plant virus species might well not exist, or can be surmounted by other viruses, implying that severe bottlenecks during host colonization do not necessarily apply to all plant-infecting viruses.

Epstein-Barr Virus Latent Membrane Protein 1 Genetic Variability in Peripheral Blood B Cells and Oropharyngeal Fluids

“…Our results extend these findings and suggest that this is a general phenomenon of the Herpesviridae family, although the factors contributing to the diversity remain unclear. Population bottlenecks associated with transmission and dissemination have been described in RNA viruses, such as HIV-1 (63), and, to a lesser extent, in DNA viruses (64), including the herpesvirus HCMV (19). The mutation rates of DNA viruses, and of herpesviruses specifically, are significantly lower than those of RNA viruses (65).…”

Dynamics of the Establishment of Systemic Potyvirus Infection: Independent yet Cumulative Action of Primary Infection Sites

“…Third, the combination of TEV and tobacco is in some respects unusual; the probability that a primary infection focus causes systemic infection is practically 1, and there does not appear to be a strong genetic bottleneck during the colonization of systemically infected leaves (36,37). Although Cauliflower mosaic virus infection can be similar to TEV in this respect (27), other viruses clearly show different infection dynamics (18,19,25,29). Fourth, our results suggest that the systemic tissue of the plant can be largely saturated by virion production of a small number of primary infection foci.…”

Demographics of Natural Oral Infection of Mosquitos by Venezuelan Equine Encephalitis Virus

“…The methodology used is based on F st statistics and uses genetic variance within and between populations (i.e., the virus populations in the inoculum and midguts) to estimate the effective population size (13). Bottleneck sizes ranged from several tens in the enzootic model to several hundred genomes in the epizootic model ( ).…”