Publications by authors named "Simkin A"

Increasing artemisinin partial resistance (ArtR) due to mutations in the gene encoding Kelch13 ( ) protein in eastern Africa is of urgent concern, and mutations, such as P441L, continue to emerge. We used an amplicon deep-sequencing panel to estimate the prevalence of ArtR mutations in samples collected between 2018 and 2023 in southern Zambia. P441L was present in 30 of 501 samples (6%), and prevalence increased over time (0% to 7.

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  • Plasmodium ovale curtisi (Poc) and Plasmodium ovale wallikeri (Pow) are two distinct malaria parasites now recognized in Africa and Asia, previously thought to be one species.
  • A genomic study analyzed 25 newly sequenced isolates from Central and East Africa, finding that genetic variations are geographically clustered and predominantly monoclonal.
  • Poc exhibits higher genetic diversity than Pow, and both species show evidence of selective pressure on certain genes, indicating their adaptation and resilience despite malaria control efforts.
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  • Plasmodium vivax is increasingly problematic in tropical regions, particularly where Plasmodium falciparum is declining, due to its ability to cause relapse infections that hinder treatment efforts.
  • Researchers developed four specialized molecular inversion probe (MIP) genotyping panels targeting key genetic variations in P. vivax, aiming to better understand its population structure and resistance mechanisms.
  • Analysis using these panels on 866 infections in the Peruvian Amazon revealed significant findings, including transmission networks, gene mutations related to drug resistance, and potential vaccine targets, suggesting these tools can enhance research and control of P. vivax globally.
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Background: Resistance to antimalarial drugs remains a major obstacle to malaria elimination. Multiplexed, targeted amplicon sequencing is being adopted for surveilling resistance and dissecting the genetics of complex malaria infections. Moreover, genotyping of parasites and detection of molecular markers drug resistance in resource-limited regions requires open-source protocols for processing samples, using accessible reagents, and rapid methods for processing numerous samples including pooled sequencing.

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  • * Researchers sequenced the genomes of 25 isolates from Central and East Africa, revealing that these isolates are mostly monoclonal and show genetic patterns that correlate with geographical locations.
  • * Results indicated that one species has lower genetic diversity than the other, and both exhibit signs of selective pressures on specific genes, suggesting that their evolutionary paths and responses to control measures in malaria have unique aspects based on their history.
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  • A large genomic study on African malaria isolates was conducted, analyzing 77 samples from Cameroon, the Democratic Republic of the Congo, Nigeria, and Tanzania collected between 2015 and 2021.
  • The study found no geographic population structure among the isolates, indicating that they are panmictic and mixing freely across different regions.
  • While there were no clear indicators of significant resistance genes, certain erythrocyte invasion ligands and antimalarial resistance markers showed signs of selective pressure, suggesting that the malaria population is recovering from a past decline.
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In this study, we assessed 43 accessions of sorghum from 16 countries across three continents. Our objective was to identify stomatal and photosynthetic traits that could be exploited in breeding programmes to increase photosynthesis without increasing water use under dynamic light environments. Under field conditions, sorghum crops often have limited water availability and are exposed to rapidly fluctuating light intensities, which influences both photosynthesis and stomatal behaviour.

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  • The study investigates the prevalence of the Arg561His mutation in the Plasmodium falciparum k13 gene and other antimalarial resistance markers in Tanzania, particularly near the border with Rwanda, due to rising concerns about resistance in the region.* -
  • A total of 6855 blood samples from malaria-positive individuals were collected and genotyped, revealing an overall mutation prevalence of 7.7% in the Kagera region, with higher rates closer to Rwanda.* -
  • Genetic analysis indicates a possible connection between some local P. falciparum strains and those previously recorded in Rwanda, suggesting a regional spread of resistance.*
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Cherry () fruits are important sources of vitamins, minerals, and nutrients in the human diet; however, they contain a large stone, making them inconvenient to eat 'on the move' and process. The exogenous application of gibberellic acid (GA) can induce parthenocarpy in a variety of fruits during development. Here, we showed that the application of GA to sweet cherry unpollinated pistils acted as a trigger for fruit set and permitted the normal formation of fruit up to a period of twenty-eight days, indicating that gibberellins are involved in the activation of the cell cycle in the ovary wall cells, leading to fruit initiation.

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This study reveals striking differences in the content and composition of hydrophilic and lipophilic compounds in blackcurrant buds (Ribes nigrum L., cv. Ben Klibreck) resulting from winter chill or chemical dormancy release following treatment with ERGER, a biostimulant used to promote uniform bud break.

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  • Transmission of malaria is on the rise in tropical regions and poses challenges for treatment, leading to relapse infections.
  • Researchers developed four specialized molecular inversion probe (MIP) genotyping panels to analyze genetic variations related to antimalarial resistance and vaccines, focusing on specific SNPs.
  • The study analyzed 866 malaria infections in the Peruvian Amazon, identifying key transmission networks and genetic features that could enhance malaria control efforts in other affected areas.
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Background: Emergence of artemisinin partial resistance (ART-R) in is a growing threat to the efficacy of artemisinin combination therapies (ACT) and the efforts for malaria elimination. The emergence of Kelch13 (K13) R561H in Rwanda raised concern about the impact in neighboring Tanzania. In addition, regional concern over resistance affecting sulfadoxine-pyrimethamine (SP), which is used for chemoprevention strategies, is high.

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The Calvin-Benson-Bassham (CBB) cycle is the ancestral CO assimilation pathway and is found in all photosynthetic organisms. Biochemical extensions to the CBB cycle have evolved that allow the resulting pathways to act as CO concentrating mechanisms, either spatially in the case of C photosynthesis or temporally in the case of Crassulacean acid metabolism (CAM). While the biochemical steps in the C and CAM pathways are known, questions remain on their integration and regulation with CBB cycle activity.

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Improving photosynthesis is a promising avenue to increase food security. Studying photosynthetic traits with the aim to improve efficiency has been one of many strategies to increase crop yield but analyzing large data sets presents an ongoing challenge. Machine learning (ML) represents a ubiquitous tool that can provide a more elaborate data analysis.

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Several long-term studies have provided strong support demonstrating that growing crops under elevated [CO] can increase photosynthesis and result in an increase in yield, flavour and nutritional content (including but not limited to Vitamins C, E and pro-vitamin A). In the case of tomato, increases in yield by as much as 80% are observed when plants are cultivated at 1000 ppm [CO], which is consistent with current commercial greenhouse production methods in the tomato fruit industry. These results provide a clear demonstration of the potential for elevating [CO] for improving yield and quality in greenhouse crops.

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This manuscript identifies cherry orthologues of genes implicated in the development of pericarpic fruit and pinpoints potential options and restrictions in the use of these targets for commercial exploitation of parthenocarpic cherry fruit. Cherry fruit contain a large stone and seed, making processing of the fruit laborious and consumption by the consumer challenging, inconvenient to eat 'on the move' and potentially dangerous for children. Availability of fruit lacking the stone and seed would be potentially transformative for the cherry industry, since such fruit would be easier to process and would increase consumer demand because of the potential reduction in costs.

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Background: Men who have sex with men (MSM) are consistently burdened by HIV at higher levels than other adults. While HIV prevention programs for MSM are growing in coverage and quality, HIV incidence remains high. In response, pre-exposure prophylaxis (PrEP) was introduced in 2019 to support HIV risk reduction among MSM in Cameroon.

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Fruits are an important source of vitamins, minerals and nutrients in the human diet. They also contain several compounds of nutraceutical importance that have significant antioxidant and anti-inflammatory roles, which can protect the consumer from diseases, such as cancer, and cardiovascular disease as well as having roles in reducing the build-up of LDL-cholesterol in blood plasma and generally reduce the risks of disease and age-related decline in health. Cherries contain high concentrations of bioactive compounds and minerals, including calcium, phosphorous, potassium and magnesium, and it is, therefore, unsurprising that cherry consumption has a positive impact on health.

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In this study, four tobacco transformants overexpressing the inorganic carbon transporter B gene (ictB) were screened for photosynthetic performance relative to the wild type (WT) in field-based conditions. The WT and transgenic tobacco plants were evaluated for photosynthetic performance to determine the maximum rate of carboxylation (Vc, max), maximum rate of electron transport (Jmax), the photosynthetic compensation point (Γ*), quantum yield of PSII (ΦPSII), and mesophyll conductance (gm). Additionally, all plants were harvested to compare differences in above-ground biomass.

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Article Synopsis
  • Photosynthetic pigments, primarily chlorophyll, carotenoids, and phycobilins, are essential for light absorption in photosynthetic organisms like plants, algae, and cyanobacteria.
  • These pigments help plants adapt to varying light conditions, with chlorophyll absorbing different wavelengths, while carotenoids protect against photodamage and enhance light capture.
  • The review highlights how understanding and manipulating these pigments can lead to advancements in crop yields by improving light harvesting and photosynthetic efficiency.
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  • Fruits are essential food sources packed with bioactive compounds that change during ripening, showing a color transformation linked to pigments like chlorophyll, carotenoids, and anthocyanins.
  • The production and breakdown of these pigments are influenced by hormonal, genetic, and environmental factors, and understanding these processes can lead to biotechnological methods to boost desired pigments.
  • The review highlights the significance of pigments in enhancing the nutritional and industrial value of fruits, making them beneficial for harvesters, traders, and consumers by improving biofortification and harvest predictions.
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Carotenoids and apocarotenoids are diverse classes of compounds found in nature and are important natural pigments, nutraceuticals and flavour/aroma molecules. Improving the quality of crops is important for providing micronutrients to remote communities where dietary variation is often limited. Carotenoids have also been shown to have a significant impact on a number of human diseases, improving the survival rates of some cancers and slowing the progression of neurological illnesses.

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Objectives: HIV pre-exposure prophylaxis (PrEP) may change serosorting patterns. We examined the influence of serosorting on the population-level HIV transmission impact of PrEP, and how impact could change if PrEP users stopped serosorting.

Design: We developed a compartmental HIV transmission model parameterized with bio-behavioural and HIV surveillance data among MSM in Canada.

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Previous studies have demonstrated that the independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multigene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or the overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with the expression of the red algal protein cytochrome c, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved.

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