A Population Genetics Perspective on Geminivirus Infection

Abstract

The selective accumulation of both DNA components of a bipartite geminivirus, Abutilon mosaic virus, was recorded during early systemic infection of Nicotiana benthamiana plants. Purified nuclei were diagnosed for viral DNA using hybridization specific for DNA A or DNA B to detect these individual genome components either alone or both simultaneously by dual-color staining. Although this virus needs both components for symptomatic infection, DNA A alone was transported to upper leaves, where it was imported into phloem nuclei and replicated autonomously. The coinfection with DNA A and DNA B revealed an independent spread of both molecules, which resulted in a stochastic distribution of DNA A-and DNA A/B-infected nuclei. A population genetics evaluation of the respective frequencies was compared to a model computation. This elucidated a surprisingly simple relationship between the initial frequencies of the viral DNA components and the number of susceptible cells during the course of early systemic infection. IMPORTANCEFor bipartite begomoviruses, DNA B-independent long-distance spread of DNA A has been described before, but it has never been shown whether viral DNA A alone invades nuclei of systemic tissues and replicates therein. This is demonstrated now for the first time. During infection with DNA A and DNA B, a similar solitary spread of DNA A can be recognized at early stages. We describe a population genetics model of how the hit probabilities of DNA A and DNA B for susceptible cells determine the relative frequencies of either genome component during the course of infection.

Novel circular DNA virus identified in Opuntia discolor (Cactaceae) that codes for proteins with similarity to those of geminiviruses

“…It has been documented for some bipartite begomoviruses that DNA-A components are able to replicate and infect N. benthamiana systematically without the presence of movement protein-encoding DNA-B components [38][39][40][41][42][43][44][45]. In fact, an experimental study showed that the DNA-A of the begomovirus abutilon mosaic virus can spread through the plant and enter the cell nucleus for replication in an independent way, even in the presence of DNA-B [43]. Although the infectivity experiments with utkilio virus are consistent with those for begomoviruses, they should not be considered to be definitive, and more experimental work is necessary to determine the role of the DNA-B in infections.…”

“…It is interesting, nonetheless, that utkilio virus DNA-A was able to spread systemically and replicate within N. benthamiana. It has been documented for some bipartite begomoviruses that DNA-A components are able to replicate and infect N. benthamiana systematically without the presence of movement protein-encoding DNA-B components [38][39][40][41][42][43][44][45]. In fact, an experimental study showed that the DNA-A of the begomovirus abutilon mosaic virus can spread through the plant and enter the cell nucleus for replication in an independent way, even in the presence of DNA-B [43].…”

Mixed-Infection of Papaya Ring Spot Virus and Tomato Leaf Curl New Delhi Virus in Coccinia grandis in India

“…After that the membrane was UV-cross linked for 30 min under UVCross Linker (GeNei TM, India). Prehybridization, hybridization and washing of membrane were done according to the southern blot analysis protocol using biotinlabeled probes (Weigel et al, 2015).…”

Differential Effects of RNA-Dependent RNA Polymerase 6 (RDR6) Silencing on New and Old World Begomoviruses in Nicotiana benthamiana

“…Samples from the TYLCSV-infected plants of both genotypes, which showed similar virus accumulation levels, were also analysed in parallel. Due to the overall limited percentages of nuclei infected by these phloem-limited viruses in wt N. benthamiana (about 1% of leaf nuclei for AbMV [62] and up to about 7% for TYLCSV [41]), numerous consecutive sections of stems, leaves, apical, and flower buds had to be examined to ensure correct localization and statistically significant quantitative data. For the optimal identification of cell and tissue types, virus DNA was detected using precipitated stains in semi-thin sections, as described in [50].…”