Effects of thrips feeding on tospovirus transmission in chrysanthemum

The introduction and rapid spread of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) in Western Europe since the 1980s led to a considerable increase of losses in different, mainly ornamental crops due to tomato spotted wilt tospovirus (TSWV) infections. Besides the losses inflicted by TSWV, F. occidentalis itself is also an important pest on many of these crops. Chrysanthemum is one of those crops which is affected by both TSWV and its vector. Breeding and selection of this plant species has resulted in the identification of a few chrysanthemum cultivars with some partial resistance to thrips. However, resistant cultivars to TSWV have not been successfully developed yet, meaning that the control of TSWV has to rely on other strategies. Besides sanitation programs, other successful strategies to control TSWV or F. occidentalis are currently not available.To develop durable and effective control measures and integrated pest management strategies, more detailed knowledge of the precise interactions between the virus, its vector and the threatened crop is required. Since transmission of TSWV is associated with ingestion of food, the feeding behaviour of thrips is one of the most determining factors in virus transmission. This study was therefore aimed to analyse the interactions between virus, vector and (chrysanthemum) plant in relation to thrips feeding.Tospovirus is acquired by larvae and transmitted by old second instar larvae and adults after their emergence. As a first feature, the ability of larvae to acquire TSWV was analysed in relation to their age. The results obtained in a study with several F. occidentalis populations showed that the ability to acquire virus (defined as ingestion of virus by larvae, subsequently developing in viruliferous adults), dropped with the age of larvae. A notable result was obtained with one of the populations (NL3), which could only acquire TSWV when larvae were in their first larval (L1) stage.Besides the age of the larvae at which they acquire virus, other parameters such as the F. occidentalis population involved, the feeding behaviour by the amount of food ingested, the virus species acquired and the host plant involved were studied for their effect on virus acquisition and transmission. Large and significant differences were found in TSWV transmission competencies between fourteen F. occidentalis populations which originated from different countries all over the world. These differences were not affected by the amount of virus ingested or the host used as virus source. However, the use of another tospovirus species, impatiens necrotic spot virus (INSV), influenced the transmission differences between populations. The transmission efficiencies found appeared to be rather constant, supporting the view that the competence of a population to transmit TSWV is a stable, and, therefore, inherited property.The efficiency at which the F. occidentalis populations transmitted INSV was higher than that of TSWV. This observation confirms earlier reports that the different tospovirus species are transmitted at distinct rates by the same thrips population. It is likely that various isolates of TSWV will also be transmitted at different rates by one and the same F. occidentalis population as has been shown for some Thrips tabaci populations. In contrast to TSWV, INSV is acquired by L1s as well as second larval instars (L2s) of the NL3 population.Further studies revealed that males of F. occidentalis are more efficient TSWV transmitters than females. This feature was found for all fourteen F. occidentalis populations tested. The differences in virus transmission competencies between both sexes can be explained by differences in their feeding behaviour. Males produce less silvery scars and make more frequent inoculation punctures than females. These punctures may represent the event during which the virus is successfully transmitted, as cells remain viable allowing virus to be replicated after virus-containing saliva injection. In addition, cells which are pierced and drained in the feeding process (resulting in silvery scars) are probably so destroyed that they will not support virus replication.The different efficiencies by which males and females transmit virus may have an impact on the spread of the virus in a crop. Males may infect more plants than females as they show a higher mobility and the sex ratios in flights are male-biased. However, the contribution of males to the spread may be compensated or outweighed by the greater life expectation of females. Quantification of the development of an epidemic in terms of which part is caused by males and which by females, will be extremely difficult as the ratio between males and females will change continuously and their age can not accurately be determined.To analyse whether thrips resistant chrysanthemum cultivars could effectively be used to control TSWV spread in this crop, fifteen cultivars were assessed for their susceptibility for this virus. All cultivars were susceptible, irrespective their degree of thrips resistance. However, the number of plants that attracted an infection varied for each cultivar. lt appeared in this study that the infection proceeds poorly in the infected plants and that the virus became unevenly distributed over the plant. A consequence of these observations is that in the chrysanthemum crop the virus will disperse slowly from primary infected plants. No L1s emerging on such plants, or only a small proportion of them, will acquire virus. With the development of the infection in the plant and development of the thrips population, more larvae will be able to acquire virus and thus become transmitters. This means that the early developing population of thrips found on primary infected plants by incoming (dispersing) adults will hardly contribute to the (intercrop) spread of the virus an that, with time, the infection pressure may increase from these primary infected plants. Studies on assessing the development of viruliferous thrips in a population on a primary infected chrysanthemum plant should enhance our understanding of TSWV spread in chrysanthemum.In most cases, tospovirus infections have been attributed to virus introduction from sources located outside the crop, and less to secondary (intercrop) spread in the crop as reported for groundnut, tomato and pepper. The incidence of TSWV infections in the Dutch chrysanthemum crops is low, despite the fact that TSWV transmission to chrysanthemum occurs highly efficiently. Since the virus is not seed transmitted, the first infections may arise as a result from primary infections, subsequently followed by some secondary spread.Using plants in testing the susceptibility of chrysanthemum for TSWV and vector resistance is a time- and labour-consuming activity. An expeditious leaf disk assay was introduced to assess this susceptibility. This assay was also used to quantify TSWV transmission to a partially vector-resistant and a susceptible cultivar. It was shown that the inoculation access period in which 50% of the disks became infected (IAP 50 ) was shorter for a partially vector-resistant cultivar than for a susceptible cultivar, indicating that TSWV is more efficiently transmitted to the more vector resistant cultivar. This may be the result of a different feeding behaviour on the less preferred, partially resistant cultivar, resulting in a higher frequency of inoculation punctures in a unit of time, and subsequently in greater probability of successful transmission.The spread of TSWV will certainly be affected by the attractiveness of the plant as food source of the thrips. The lower development rate of viruliferous thrips and the shorter life expectancy on partially vector-resistant cultivars likely reduces secondary spread. On the contrary, the mobility and dispersal of thrips and subsequent TSWV transmission in enhanced on partially resistant vector plants, and hence, the use of vector-resistant cultivars may not under all circumstances lead to an effective control of TSWV spread.</p

Mechanism and reaction coordinate of directional charge separation in bacterial reaction centers

Solid state NMR/Biophysical Organic Chemistr

Variation in tospovirus transmission between populations of Frankliniella occidentalis (Thysanoptera: Thripidae)

Fourteen populations of the western flower thrips Frankliniella occidentalisPergande, originating from different hosts and countries in Asia, Europe, North America and New Zealand, were analysed for their competency and efficiency to transmit tomato spotted wilt virus (TSWV). All populations acquired and subsequently transmitted the virus, and were thus competent to transmit. They show marked differences in their efficiency, expressed as the percentage of transmitting adults. Efficiencies varied from 18 or a F. occidentalis population from the USA (US2) to 75␈r a population from Israel (IS2). The differences between populations were not affected by the amount of virus ingested or by the host plant used. However, the tospovirus species studied and age at which the larvae acquired the virus affected the efficiency to transmit. First instar larvae of the NL3 population from The Netherlands were able to acquire tomato spotted wilt virus, whereas second instar larvae failed to do so. However, both instars of this population acquired impatiens necrotic spot virus (INSV), another tospovirus. This and tomato spotted wilt virus were both acquired by both larval stages of the populations IS2 and US2, although their ability to acquire virus decreased with their age. Hence, it is likely that, in general, both instar larvae of most F. occidentalis populations are competent to acquire both tospoviruses. These results show that large differences exist in the efficiency by which tomato spotted wilt is transmitted by the various F. occidentalis populations and that the ability to acquire tospovirus decreases with the age of the larva

DNA methylation dynamics during intestinal stem cell differentiation reveals enhancers driving gene expression in the villus

Background: DNA methylation is of pivotal importance during development. Previous genome-wide studies identified numerous differentially methylated regions upon differentiation of stem cells, many of them associated with transcriptional start sites. Results: We present the first genome-wide, single-base-resolution view into DNA methylation dynamics during differentiation of a mammalian epithelial stem cell: the mouse small intestinal Lgr5+ stem cell. Very little change was observed at transcriptional start sites and our data suggest that differentiation-related genes are already primed for expression in the stem cell. Genome-wide, only 50 differentially methylated regions were identified. Almost all of these loci represent enhancers driving gene expression in the differentiated part of the small intestine. Finally, we show that binding of the transcription factor Tcf4 correlates with hypo-methylation and demonstrate that Tcf4 is one of the factors contributing to formation of differentially methylated regions. Conclusions: Our results reveal limited DNA methylation dynamics during small intestine stem cell differentiation and an impact of transcription factor binding on shaping the DNA methylation landscape during differentiation of stem cells in vivo

"MY PKU": increasing self-management in patients with phenylketonuria. A randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine metabolism. The inability to convert phenylalanine (Phe) into tyrosine causes Phe to accumulate in the body. Adherence to a protein restricted diet, resulting in reduced Phe levels, is essential to prevent cognitive decline. Frequent evaluation of plasma Phe levels and, if necessary, adjustment of the diet are the mainstay of treatment. We aimed to assess whether increased self-management of PKU patients and/or their parents is feasible and safe, by providing direct online access to blood Phe values without immediate professional guidance.</p> <p>Methods</p> <p>Thirty-eight patients aged ≥ 1 year participated in a 10 month randomized controlled trial. Patients were randomized into a study group (1) or a control group (2). Group 2 continued the usual procedure: a phone call or e-mail by a dietician in case of a deviant Phe value. Group 1 was given a personal "My PKU" web page with a graph of their recent and previous Phe values, online general information about the dietary treatment and the Dutch PKU follow-up guidelines, and a message-box to contact their dietician if necessary. Phe values were provided on "My PKU" without advice. Outcome measures were: differences in mean Phe value, percentage of values above the recommended range and Phe sample frequency, between a 10-month pre-study period and the study period in each group, and between the groups in both periods. Furthermore we assessed satisfaction of patients and/or parents with the 'My PKU' procedure of online availability.</p> <p>Results</p> <p>There were no significant differences in mean Phe value, percentage of values above recommended range or in frequency of blood spot sampling for Phe determination between the pre-study period and the study period in each group, nor between the 2 groups during the periods. All patients and/or parents expressed a high level of satisfaction with the new way of disease management.</p> <p>Conclusions</p> <p>Increased self-management in PKU by providing patients and/or parents their Phe values without advice is feasible and safe and is highly appreciated.</p> <p>Trial registration</p> <p>The trial was registered with The Netherlands National Trial Register (<a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=1171">NTR #1171</a>) before recruitment of patients.</p

Quantum Holonomy in Three-dimensional General Covariant Field Theory and Link Invariant

We consider quantum holonomy of some three-dimensional general covariant non-Abelian field theory in Landau gauge and confirm a previous result partially proven. We show that quantum holonomy retains metric independence after explicit gauge fixing and hence possesses the topological property of a link invariant. We examine the generalized quantum holonomy defined on a multi-component link and discuss its relation to a polynomial for the link.Comment: RevTex, 12 pages. The metric independence of path integral measure is justified and the case of multi-component link is discussed in detail. To be published in Physical Review

Considerable Variability Among Transplant Nephrologists in Judging Deceased Donor Kidney Offers

Introduction: Transplant clinicians may disagree on whether or not to accept a deceased donor kidney offer. We investigated the interobserver variability between transplant nephrologists regarding organ acceptance and whether the use of a prediction model impacted their decisions.Methods: We developed an observational online survey with 6 real-life cases of deceased donor kidneys offered to a waitlisted recipient. Per case, nephrologists were asked to estimate the risk of adverse outcome and whether they would accept the offer for this patient, or for a patient of their own choice, and how certain they felt. These questions were repeated after revealing the risk of adverse outcome, calculated by a validated prediction model. Results: Sixty Dutch nephrologists completed the survey. The intraclass correlation coefficient of their estimated risk of adverse outcome was poor (0.20, 95% confidence interval [CI] 0.08–0.62). Interobserver agreement of the decision on whether or not to accept the kidney offer was also poor (Fleiss kappa 0.13, 95% CI 0.129–0.130). The acceptance rate before and after providing the outcome of the prediction model was significantly influenced in 2 of 6 cases. Acceptance rates varied considerably among transplant centers. Conclusion: In this study, the estimated risk of adverse outcome and subsequent decision to accept a suboptimal donor kidney varied greatly among transplant nephrologists. The use of a prediction model could influence this decision and may enhance nephrologists’ certainty about their decision.</p

Why is it difficult to implement e-health initiatives? A qualitative study

&lt;b&gt;Background&lt;/b&gt; The use of information and communication technologies in healthcare is seen as essential for high quality and cost-effective healthcare. However, implementation of e-health initiatives has often been problematic, with many failing to demonstrate predicted benefits. This study aimed to explore and understand the experiences of implementers - the senior managers and other staff charged with implementing e-health initiatives and their assessment of factors which promote or inhibit the successful implementation, embedding, and integration of e-health initiatives.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Methods&lt;/b&gt; We used a case study methodology, using semi-structured interviews with implementers for data collection. Case studies were selected to provide a range of healthcare contexts (primary, secondary, community care), e-health initiatives, and degrees of normalization. The initiatives studied were Picture Archiving and Communication System (PACS) in secondary care, a Community Nurse Information System (CNIS) in community care, and Choose and Book (C&#38;B) across the primary-secondary care interface. Implementers were selected to provide a range of seniority, including chief executive officers, middle managers, and staff with 'on the ground' experience. Interview data were analyzed using a framework derived from Normalization Process Theory (NPT).&lt;p&gt;&lt;/p&gt; &lt;b&gt;Results&lt;/b&gt; Twenty-three interviews were completed across the three case studies. There were wide differences in experiences of implementation and embedding across these case studies; these differences were well explained by collective action components of NPT. New technology was most likely to 'normalize' where implementers perceived that it had a positive impact on interactions between professionals and patients and between different professional groups, and fit well with the organisational goals and skill sets of existing staff. However, where implementers perceived problems in one or more of these areas, they also perceived a lower level of normalization.&lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusions&lt;/b&gt; Implementers had rich understandings of barriers and facilitators to successful implementation of e-health initiatives, and their views should continue to be sought in future research. NPT can be used to explain observed variations in implementation processes, and may be useful in drawing planners' attention to potential problems with a view to addressing them during implementation planning

Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures

Photo-ionization is the accepted mechanism for the propagation of positive streamers in air though the parameters are not very well known; the efficiency of this mechanism largely depends on the presence of both nitrogen and oxygen. But experiments show that streamer propagation is amazingly robust against changes of the gas composition; even for pure nitrogen with impurity levels below 1 ppm streamers propagate essentially with the same velocity as in air, but their minimal diameter is smaller, and they branch more frequently. Additionally, they move more in a zigzag fashion and sometimes exhibit a feathery structure. In our simulations, we test the relative importance of photo-ionization and of the background ionization from pulsed repetitive discharges, in air as well as in nitrogen with 1 ppm O2 . We also test reasonable parameter changes of the photo-ionization model. We find that photo- ionization dominates streamer propagation in air for repetition frequencies of at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition frequency has to be included above 1 Hz. Finally, we explain the feather-like structures around streamer channels that are observed in experiments in nitrogen with high purity, but not in air.Comment: 12 figure