The use of maize streak virus (MSV) replication-associated protein mutants in the development of MSV-resistant plants

Bibliography: pages 170-194.Maize streak virus (MSV) is the type member of the Mastrevirus genus of the Geminiviridae. As the causal agent of maize streak disease (MSD), MSV is the most significant pathogen of maize in Africa, resulting in crop yield losses of up to 100%. Transmitted by leafhoppers (Cicadulina spp.), MSV is indigenous to Africa and neighbouring Indian Ocean Islands. Despite maize being a crucial staple food crop in Africa, the average maize yield per hectare in Africa is the lowest in the world, leading to food shortages and famine. A major contributing factor to these low yields is MSD. To genetically engineer MSV-resistant maize using the pathogen-derived resistance (PDR) strategy, the viral replication-associated (Rep) protein gene was targeted, whose multifunctional products Rep and RepA are the only viral proteins essential for replication. Rep constructs had previously been made containing deleterious mutations in several conserved amino acid motifs. In this study, these mutants and the wild type Rep gene were truncated to remove key motifs involved in viral replication. A quantitative PCR assay was developed to determine the effects of the mutant and truncated Reps on viral replication in black Mexican sweetcorn (BMS) suspension cells. The MSVsensitive grass Digitaria sanguinalis was then transformed with Rep constructs that inhibited MSV replication in BMS, and transgenic lines were tested for virus resistance. Several plants of a D. sanguinalis line transgenic for a mutated full-length Rep gene showed excellent resistance (immunity) to MSV, but the transgene had negative effects on aspects of plant growth and development. Transformation with a mutated/truncated Rep gene resulted in healthy fertile transgenic D. sanguinalis plants, many of which showed good MSV resistance. Fertile maize (Hi-II) T 1 transgenic plants expressing the truncated/mutated Rep gene have been obtained, the offspring of which will be tested for resistance to MSV. Considering the success in achieving MSV-resistant D. sanguinalis, there is good reason to believe that the transgenic maize will too be resistant to MSV

A physical activity intervention in a Bingo club: Significance of the setting

Objective:  A Bingo club was selected for the design and delivery of a health intervention (Well!Bingo) in order to engage with older women living in areas areas of socio-economic disadvantage. In the light of our experience, we discuss the significance of the setting in relation to a typology of health promotion settings.  Design and Setting:  The Well!Bingo physical activity intervention was piloted in a Bingo club in Scotland.  Methods:  In a pilot feasibility study, women were recruited face-to-face at a Bingo club over two weeks. The 12-week intervention consisted of three different structured exercise sessions per week, followed by refreshments, with trained instructors delivering a schedule of simple pre-defined health messages. Participants completed a baseline questionnaire, and in-depth qualitative interviews were carried out with participants and instructors post-intervention. For this paper, using the framework method, we retrieved and analysed the data coded as relating to the setting.  Results:  Eighteen women (55-92 years) took part in intervention sessions. Half lived in areas of socio-economic deprivation. Practical and social familiarity with the setting (a sense of belonging and being with people like themselves) encouraged them to take part, and implicit features of the setting may have enhanced recruitment and effectiveness.  Discussion:  In settings-based health promotion, a Bingo club could be seen as a ‘passive' setting, simply facilitating access to a target population. It cannot be an ‘active setting', because health promotion will never be a core activity and features cannot be drawn upon to influence change. However, calling it a passive setting overlooks the importance of characteristics that may enhance recruitment and effectiveness. This highlights the need to extend current concepts of ‘passive' health promotion settings

A highly divergent South African geminivirus species illuminates the ancient evolutionary history of this family

Background. We have characterised a new highly divergent geminivirus species, Eragrostis curvula streak virus (ECSV), found infecting a hardy perennial South African wild grass. ECSV represents a new genus-level geminivirus lineage, and has a mixture of features normally associated with other specific geminivirus genera. Results. Whereas the ECSV genome is predicted to express a replication associated protein (Rep) from an unspliced complementary strand transcript that is most similar to those of begomoviruses, curtoviruses and topocuviruses, its Rep also contains what is apparently a canonical retinoblastoma related protein interaction motif such as that found in mastreviruses. Similarly, while ECSV has the same unusual TAAGATTCC virion strand replication origin nonanucleotide found in another recently described divergent geminivirus, Beet curly top Iran virus (BCTIV), the rest of the transcription and replication origin is structurally more similar to those found in begomoviruses and curtoviruses than it is to those found in BCTIV and mastreviruses. ECSV also has what might be a homologue of the begomovirus transcription activator protein gene found in begomoviruses, a mastrevirus-like coat protein gene and two intergenic regions. Conclusion. Although it superficially resembles a chimaera of geminiviruses from different genera, the ECSV genome is not obviously recombinant, implying that the features it shares with other geminiviruses are those that were probably present within the last common ancestor of these viruses. In addition to inferring how the ancestral geminivirus genome may have looked, we use the discovery of ECSV to refine various hypotheses regarding the recombinant origins of the major geminivirus lineages. © 2009 Varsani et al; licensee BioMed Central Ltd

A highly divergent South African geminivirus species illuminates the ancient evolutionary history of this family

Background: We have characterised a new highly divergent geminivirus species, Eragrostis curvula streak virus (ECSV), found infecting a hardy perennial South African wild grass. ECSV represents a new genus-level geminivirus lineage, and has a mixture of features normally associated with other specific geminivirus genera. Results: Whereas the ECSV genome is predicted to express a replication associated protein (Rep) from an unspliced complementary strand transcript that is most similar to those of begomoviruses, curtoviruses and topocuviruses, its Rep also contains what is apparently a canonical retinoblastoma related protein interaction motif such as that found in mastreviruses. Similarly, while ECSV has the same unusual TAAGATTCC virion strand replication origin nonanucleotide found in another recently described divergent geminivirus, Beet curly top Iran virus (BCTIV), the rest of the transcription and replication origin is structurally more similar to those found in begomoviruses and curtoviruses than it is to those found in BCTIV and mastreviruses. ECSV also has what might be a homologue of the begomovirus transcription activator protein gene found in begomoviruses, a mastrevirus-like coat protein gene and two intergenic regions. Conclusion: Although it superficially resembles a chimaera of geminiviruses from different genera, the ECSV genome is not obviously recombinant, implying that the features it shares with other geminiviruses are those that were probably present within the last common ancestor of these viruses. In addition to inferring how the ancestral geminivirus genome may have looked, we use the discovery of ECSV to refine various hypotheses regarding the recombinant origins of the major geminivirus lineages

Experimental evidence indicating that mastreviruses probably did not co-diverge with their hosts

Background. Despite the demonstration that geminiviruses, like many other single stranded DNA viruses, are evolving at rates similar to those of RNA viruses, a recent study has suggested that grass-infecting species in the genus Mastrevirus may have co-diverged with their hosts over millions of years. This "co-divergence hypothesis" requires that long-term mastrevirus substitution rates be at least 100,000-fold lower than their basal mutation rates and 10,000-fold lower than their observable short-term substitution rates. The credibility of this hypothesis, therefore, hinges on the testable claim that negative selection during mastrevirus evolution is so potent that it effectively purges 99.999% of all mutations that occur. Results. We have conducted long-term evolution experiments lasting between 6 and 32 years, where we have determined substitution rates of between 2 and 3 × 10 -4substitutions/site/year for the mastreviruses Maize streak virus (MSV) and Sugarcane streak Réunion virus (SSRV). We further show that mutation biases are similar for different geminivirus genera, suggesting that mutational processes that drive high basal mutation rates are conserved across the family. Rather than displaying signs of extremely severe negative selection as implied by the co-divergence hypothesis, our evolution experiments indicate that MSV and SSRV are predominantly evolving under neutral genetic drift. Conclusion. The absence of strong negative selection signals within our evolution experiments and the uniformly high geminivirus substitution rates that we and others have reported suggest that mastreviruses cannot have co-diverged with their hosts. © 2009 Harkins et al; licensee BioMed Central Ltd

A new African streak virus species from Nigeria

The African streak viruses (AfSVs) are a diverse group of mastrevirus species (family Geminiviridae) that infect a wide variety of annual and perennial grass species across the African continent and its nearby Indian Ocean islands. Six AfSV species (of which maize streak virus is the best known) have been described. Here we report the full genome sequences of eight isolates of a seventh AfSV species: Urochloa streak virus (USV), sampled from various locations in Nigeria. Despite there being good evidence of recombination in many other AfSV species, we found no convincing evidence that any of the USV sequences were either inter- or intra-species recombinants. The USV isolates, all of which appear to be variants of the same strain (their genome sequences are all more than 98% identical), share less than 69% nucleotide sequence identity with other currently described AfSV species

Evidence of pervasive biologically functional secondary structures within the Genomes of Eukaryotic Single-Stranded DNA Viruses

Single-stranded DNA (ssDNA) viruses have genomes that are potentially capable of forming complex secondary structures through Watson-Crick base pairing between their constituent nucleotides. A few of the structural elements formed by such base pairings are, in fact, known to have important functions during the replication of many ssDNA viruses. Unknown, however, are (i) whether numerous additional ssDNA virus genomic structural elements predicted to exist by computational DNA folding methods actually exist and (ii) whether those structures that do exist have any biological relevance. We therefore computationally inferred lists of the most evolutionarily conserved structures within a diverse selection of animal- and plant-infecting ssDNA viruses drawn from the families Circoviridae, Anelloviridae, Parvoviridae, Nanoviridae, and Geminiviridae and analyzed these for evidence of natural selection favoring the maintenance of these structures. While we find evidence that is consistent with purifying selection being stronger at nucleotide sites that are predicted to be base paired than at sites predicted to be unpaired, we also find strong associations between sites that are predicted to pair with one another and site pairs that are apparently coevolving in a complementary fashion. Collectively, these results indicate that natural selection actively preserves much of the pervasive secondary structure that is evident within eukaryote-infecting ssDNA virus genomes and, therefore, that much of this structure is biologically functional. Lastly, we provide examples of various highly conserved but completely uncharacterized structural elements that likely have important functions within some of the ssDNA virus genomes analyzed here.Department of HE and Training approved lis

How active are women who play bingo: a cross-sectional study from the Well!Bingo project

BackgroundThe benefits of physical activity are well established, yet large numbers of people are not sufficiently active to gain health benefits. Certain population groups are less physically active than others, including older women from areas of high economic deprivation. The Well!Bingo project was established with the aim of engaging such women in the development of a health promotion intervention in a bingo club. This paper reports on the assessment of health status, physical activity and sedentary behaviour of women attending a bingo club in central Scotland, UK as part of the Well!Bingo project.MethodsWomen attending the bingo club were invited to provide information on demographic characteristics, and self-reported physical activity and sedentary behaviour via a self-complete questionnaire as part of a cross-sectional study (n = 151). A sub-sample (n = 29) wore an accelerometer for an average of 5.7 ± 1.4 days. Differences between younger (under 60 years) and older adults (60 years and over) were assessed using a chi-square test for categorical data and the independent samples t-test was used to assess continuous data (p < 0.05).ResultsThe mean age was 56.5 ± 17.7 years, with 57% living in areas of high deprivation (Scottish Index of Multiple Deprivation quintile one and two). Sixty-three percent of women (n = 87) reported they were meeting physical activity guidelines. However, objective accelerometer data showed that, on average, only 18.1 ± 17.3 min a day were spent in moderate to vigorous physical activity. Most accelerometer wear time was spent sedentary (9.6 ± 1.7 h). For both self-report and accelerometer data, older women were significantly less active and more sedentary than younger women. On average, older women spent 1.8 h more than younger women in sedentary activities per day, and took part in 21 min less moderate to vigorous physical activity (9.4 mins per day).ConclusionThe findings of this study suggest that bingo clubs are settings that attract women from areas of high deprivation and older women in bingo clubs in particular would benefit from interventions to target their physical activity and sedentary behaviour. Bingo clubs may therefore be potential intervention settings in which to influence these behaviours

Accessing and engaging women from socio-economically disadvantaged areas: a participatory approach to the design of a public health intervention for delivery in a Bingo club

Background Our aim was to use participatory methods to investigate the feasibility and acceptability of using Bingo clubs for the design and delivery of an evidence-based physical activity and/or healthy eating intervention to socio-economically disadvantaged women. This paper describes the participatory process that has resulted in a physical activity intervention for women aged >55years, ready for pilot-testing in a Bingo club setting. Methods Studies using different quantitative and qualitative approaches were conducted among customers and staff of a Bingo club in a city of 85,000 inhabitants in central Scotland. These were designed to take the views of different stakeholders into account, with a view to enhancing uptake, engagement and effectiveness with any proposed intervention. Results Sixteen relevant studies were identified in a literature review that generated ideas for intervention components. A questionnaire completed by 151 women in the Bingo club showed that almost half (47%) aged >55years were not meeting physical activity guidelines; evidence backed up by accelerometer data from 29 women. Discussions in six focus groups attended by 27 club members revealed different but overlapping motivations for attending the Bingo club (social benefits) and playing Bingo (cognitive benefits). There was some scepticism as to whether the Bingo club was an appropriate setting for an intervention, and a dietary intervention was not favoured. It was clear that any planned intervention needed to utilise the social motivation and habitual nature of attendance at the Bingo club, without taking women away from Bingo games. These results were taken forward to a 5-h long participative workshop with 27 stakeholders (including 19 Bingo players). Intervention design (form and content) was then finalised during two round table research team meetings. Conclusions It was possible to access and engage with women living in areas of socio-economic disadvantage through a Bingo club setting. A physical activity intervention for women >55years is realistic for recruitment, will address the needs of potential recipients in the Bingo club, appears to be feasible and acceptable to club members and staff, and has been designed with their input. A pilot study is underway, investigating recruitment, retention and feasibility of delivery

Symptom evolution following the emergence of maize streak virus

For pathogens infecting single host species evolutionary trade-offs have previously been demonstrated between pathogen-induced mortality rates and transmission rates. It remains unclear, however, how such trade-offs impact sub-lethal pathogen-inflicted damage, and whether these trade-offs even occur in broad host-range pathogens. Here, we examine changes over the past 110 years in symptoms induced in maize by the broad host-range pathogen, maize streak virus (MSV). Specifically, we use the quantified symptom intensities of cloned MSV isolates in differentially resistant maize genotypes to phylogenetically infer ancestral symptom intensities and check for phylogenetic signal associated with these symptom intensities. We show that whereas symptoms reflecting harm to the host have remained constant or decreased, there has been an increase in how extensively MSV colonizes the cells upon which transmission vectors feed