Multitasking in Replication Is Common among Geminiviruses

Abstract

Geminiviruses package single-stranded circular DNA and replicate via double-stranded DNA intermediates. During the past decade, increasing evidence has led to the general acceptance that their replication follows a rolling-circle replication mechanism like bacteriophages with single-stranded DNA. In a recent study, we showed that this is also true for Abutilon mosaic geminivirus (AbMV), but that this particular virus may also use a recombination-dependent replication (RDR) route in analogy to T4 phages. Because AbMV is a special case, since it has been propagated on ornamental plants for more than a hundred years, it was interesting to determine whether RDR is common among other geminiviruses. We analyzed geminiviruses from different genera and geographic origins by using BND cellulose chromatography in combination with an improved high resolution two-dimensional gel electrophoresis, and we conclude that multitasking in replication is widespread, at least for African cassava mosaic, Beet curly top, Tomato golden mosaic, and Tomato yellow leaf curl virus.Geminiviruses have spread worldwide during the past three decades, causing severe diseases in important crop plants (23,35). Several factors have promoted the epidemics: transportation of plant material, increase and diversification of insect vector populations, and recombination between geminiviruses that coinfect host plants. Geminiviruses may contain monopartite or bipartite genomes (45), and consequently recombination may occur in two different ways: by exchange of viral chromosomes (interchromosomal recombination, or "pseudorecombination" as plant virologists call this type of reassortment) (54,55,61,62) or by crossover of chromosomes (intrachromosomal recombination) (5,6,17,19,38,46,68,69). Moreover, geminiviruses are able to adopt satellite-like DNA circles which have an additional impact on pathogenesis (7,12,47). In comparison to RNA-containing plant viruses, geminiviruses are relatively prone to recombination and harbor frequent footprints of recombination events within their genomes (38). This phenomenon is conceivable on the basis of a recombination-dependent replication mode of geminiviruses as was proposed recently (26).Geminiviruses package single-stranded circular DNA in twin-shaped capsids (67) and complement their DNA by using RNA-primed DNA polymerization (49). The resulting doublestranded circular DNA is packed into minichromosomes (1, 42). New rounds of replication were originally identified by two-dimensional gel electrophoresis (48), and these results have founded a rolling-circle replication (RCR) model for geminivirus multiplication (reviewed in reference 22) in analogy to the replication of bacteriophages with single-stranded circular DNA (32). A single viral protein ("AC1," also known as "AL1" or "C1" for different virus species or "Rep" for replication-associated protein to indicate its function) is necessary and sufficient for initiation by nicking the viral origin of replication (22). The RCR mode was confirmed by direct electron-mic...

Replicative intermediates of maize streak virus found during leaf development

“…Remarkably, the CSR track was overprinted by several spots, indicating the accumulation of incomplete intermediates and implying the frequent interruption of complementary-strand DNA synthesis (Figs 2 and 3). Although evidence of CSR interruption has been detected before for other geminiviruses (Jovel et al, 2007;Preiss & Jeske, 2003), it has never been seen to this extent.…”

“…In begomoviruses and curtoviruses, recombination-dependent replication (RDR) has been identified as a third replication mode that utilizes viral covalently closed circular DNA (cccDNA) as template molecules (Alberter et al, 2005;Jeske et al, 2001;Jovel et al, 2007;Morilla et al, 2006;Pilartz & Jeske, 2003;Preiss & Jeske, 2003). Mastreviruses might behave differently from members of the other genera in the family because they are the only geminiviruses to express RepA.…”

“…Here, we use one-dimensional (1D) and two-dimensional (2D) gel electrophoresis, in combination with Southern blotting and hybridization as described previously (Jeske, 2007;Preiss & Jeske, 2003), to monitor the accumulation of MSV replicative intermediates in maize tissues at varying developmental stages. Detailed descriptions of the meth-ods, as well as the 2D blots at higher resolution (Supplementary Figs S1-S4), are provided in the supplementary material (available in JGV Online).…”

Identification and molecular characterization of a novel monopartite geminivirus associated with mulberry mosaic dwarf disease

“…These viruses have circular, single-stranded, monopartite or bipartite DNA genomes replicating in the nucleus through a combination of rolling-circle and recombination-mediated mechanisms (Gutierrez, 1999;Preiss and Jeske, 2003). Based on genome organization and number of components, the type of vector and host plants, seven geminivirus genera (Mastrevirus, Curtovirus, Topocuvirus, Becurtovirus, Eragrovirus, Turncurtovirus and Begomovirus) have been identified that comprise most of the known species (Brown et al, 2012;Fauquet et al, 2008;Varsani et al, 2014a).…”

Emerging threats of begomoviruses to the cultivation of medicinal and aromatic crops and their management strategies

“…recombination-dependent replication is responsible for generating diversity in the viral genome [118]. Recombination is an evolutionary process that effects greatly on genomic evolution of geminiviruses [21,47,49,105,109,134].…”