Variants of the SFTPA1 and SFTPA2 genes and susceptibility to tuberculosis in Ethiopia

Lungs are the central organ affected and targeted by Mycobacterium tuberculosis and immune processes in the lung are of critical importance in the pathogenesis of tuberculosis. A major lung defense against invading pathogens is provided by surfactant protein A, a multi-chain protein encoded by the SFTPA1 and SFTPA2 genes. Here, we investigated polymorphisms in the SFTPA1 and SFTPA2 genes for association with tuberculosis in 181 Ethiopian families comprising 226 tuberculosis cases. Four polymorphisms, SFTPA1 307A, SFTPA1 776T, SFTPA2 355C, and SFTPA2 751C, were associated with tuberculosis (P=0.00008; P=0.019, P=0.029 and P=0.042, respectively). Additional subgroup analysis in male, female and more severely affected patients provided evidence for SFTPA1/2-covariate interaction. Finally, out of five intragenic haplotypes identified in the SFTPA1 gene and nine identified in the SFTPA2 gene, 1A ³ was most significantly associated with tuberculosis susceptibility (P=0.026). These findings suggest that SFTPA1 and SFTPA2 modify the risk of tuberculosis susceptibility and that this risk is influenced by additional covariates.     

Metabolic engineering of a complex biochemical pathway: The lysine and threonine biosynthesis as an example

The nutritional quality of crop plants is determined by their content in essential amino acids provided in food for humans or in feed for monogastric animals. Amino acid composition of crop–based diets can be improved via manipulation of the properties of key enzymes of amino acid biosynthetic pathways by mutation and transformation. We focused on the aspartate-derived amino acid pathway producing four essential amino acids: lysine, threonine, isoleucine and methionine. Genes encoding aspartate kinase (AK) and dihydrodipicolinate synthase (DHDPS) that operate as key genes of the aspartate pathway have been cloned from Arabidopsis. Genetic and molecular studies revealed that at least five different ak genes are represented. Some of them were characterized in terms of gene and promoter structure, developmental expression and regulatory properties. In the case of dhdps, two quite identical genes have been identified and characterized at expression level. Mutated genes encoding a fully feedback-insensitive form of the DHDPS enzyme were obtained from Nicotiana sylvestris and Arabidopsis. Several chimeric constructs harbouring this mutated allele under the control of constitutive or seed-specific promoters were transferred via Agrobacterium or biolistics in various plant species. In all cases, lines with significant increase of free lysine content were obtained in vegetative organs, but the impact of the transgene in seeds is limited due to the presence of an active catabolic enzyme, lysine ketoreductase. These results show that, although dealing with a complex, highly regulated pathway, the overexpression of a single gene encoding a feedback-insensitive form of the key enzyme DHDPS exerts a significant effect on the carbon flux through the aspartate pathway towards lysine production.     

Limnological and ecological characteristics of tropical highland reservoirs in Tigray, Northern Ethiopia

The semi-arid highlands of Northern Ethiopia (Tigray) have numerous small reservoirs that have been created by microdams in an attempt to provide water supply for irrigation and livestock drinking. Although the reservoirs have substantial added value to residents, their use as water resource is jeopardized by eutrophication and a high occurrence of blooms of toxic cyanobacteria. So far, there is no systematic information available on the limnological and aquatic ecological characteristics of these dams. We carried out a standardized survey of 32 reservoirs and assessed a wide set of morphometric, abiotic and biotic variables. The sampling was performed during two seasons, September–October 2004 (end of the wet season/start of the dry season) and April–May 2005 (towards the end of the dry season). Using multivariate analysis, we revealed dominating patterns of variable associations and compared the variability in these patterns among seasons. According to standardized PCA and RDA analyses, the most important axis of variation was mainly represented by a gradient in nutrients and altitude that was also positively associated with phytoplankton biomass, suspended matter and oxygen concentration, and negatively with water transparency. For most variables, correlations between the wet and dry season were weak, which suggests that individual reservoirs behaved rather differently in their response to seasonal changes. Nevertheless, a Mantel correlation (r = 0.32; P = 0.035) showed a weak but significant overall concordance in the variable association patterns among seasons. A number of reservoirs became very shallow or fell dry in the dry season, a process that was associated with an increase in suspended matter and conductivity and a decrease in transparency. These reservoirs contained lower amounts of fish and tended to be less eutrophic than the deeper, permanent systems, as they had lower levels of phosphorus and chlorophyll-a. With multiple regression analysis, we constructed most parsimonious models in an attempt to explain the variation in key biotic variables: phytoplankton and cyanobacteria biomass, cladoceran biomass, fish biomass and the abundance of submerged vegetation. Phytoplankton and fish biomass tended to be positively related with the concentration of total phosphorus, whereas cladoceran biomass was not associated with nutrient concentrations. The positive association of fish and phytoplankton with nutrient concentrations suggests a bottom-up control, whereas the absence of an association between zooplankton and nutrient concentrations may be indicative for top-down control. The biomass of cyanobacteria was negatively related to the biomass of cladocerans (Daphnia), which likely reflects a top-down effect. Most reservoirs were turbid. The occurrence and abundance of macrophytes tended to be positively related to water transparency and was negatively associated to TP and the amount of livestock frequenting the reservoirs. However, macrophytes were not limited to clear-water reservoirs. Handling editor: L. M. Bini     

Mitochondrial neurogastrointestinal encephalomyopathy and thymidine metabolism: results and hypotheses

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disease with mitochondrial DNA (mtDNA) alterations and is caused by mutations in the nuclear gene encoding thymidine phosphorylase (TP). The cardinal clinical manifestations are ptosis, ophthalmoparesis, gastrointestinal dysmotility, cachexia, peripheral neuropathy, and leukoencephalopathy. Skeletal muscle shows mitochondrial abnormalities, including ragged-red fibers and cytochrome c oxidase deficiency, together with mtDNA depletion, multiple deletions or both. In MNGIE patients, TP mutations cause a loss-of-function of the cytosolic enzyme, TP. As a direct consequence of the TP defect, thymidine metabolism is altered. High blood levels of this nucleoside are likely to lead to mtDNA defects even in cells that do not express TP, such as skeletal muscle. We hypothesize that high concentrations of thymidine affect dNTP (deoxyribonucleoside triphosphate) metabolism in mitochondria more than in cytosol or nuclei, because mitochondrial dNTPs depend mainly on the thymidine salvage pathway, whereas nuclear dNTPs depend mostly on de novo pathway. The imbalance in the mitochondrial dNTP homeostasis affects mtDNA replication, leading to mitochondrial dysfunction.     

New approach for determination of an optimum honeybee colony’s carrying capacity based on productivity and nectar secretion potential of bee forage species

The present study was carried out to determine an optimum honeybee colony’s carrying capacity of selected valleys dominated by Ziziphus spina-christi and Acacia tortilis in the Al-Baha region, Kingdom of Saudi Arabia. The study was conducted based on the assessment of the number of colonies kept, their productivities and the existing productive bee forage resources in the target valleys with its economic implication. In the existing beekeeping practice, the average number of managed honeybee colonies introduced per square kilometer was 530 and 317 during the flowering period of Z. spina-christi and A. tortilis, respectively. Furthermore, the overall ratios of productive bee forage plants to the number of honeybee colonies introduced were 0.55 and 11.12 to Ziziphus trees and A. tortilis shrubs respectively. In the existing situation the average honey production potential of 5.21 and 0.34 kg was recorded per Ziziphus and A. tortilis plants per flowering season, respectively. The present study, revealed that the number of honeybee colonies introduced in relation to the existing bee forage potential was extremely overcrowding which is beyond the carrying capacity of bee forage resources in selected valleys and it has been observed to affect the productivities and subsequent profitability of beekeeping. The study infers that, by keeping the optimum honeybee colony’s carrying capacity of valleys (88 traditional hives/km² or 54 Langstroth hives/km² in Ziziphus field and 72 traditional hives/km² or 44 Langstroth hives/km² in A. tortilis field), profitability of beekeeping can be boosted up to 130.39% and 207.98% during Z. spina-christi and A. tortilis, flowering seasons, respectively.     

Predicting the distributions of Pouteria adolfi-friederici and Prunus africana tree species under current and future climate change scenarios in Ethiopia

Distributions of potential ranges of plant species are not yet fully known in Ethiopia where high climatic variability and vegetation types are found. This study was undertaken to predict distributions of suitable habitats of Pouteria adolfi-friederici and Prunus africana under current and two future climate scenarios (RCP 4.5 and RCP 8.5 in 2050 and 2070) in Ethiopia. Eleven environmental variables with less correlation coefficients (r < 0.7) were used to make the prediction. Shifting in extents of habitat suitability and effects of elevation, solar radiation and topographic position in relation to the current and future climatic scenarios were statistically analysed using independent t-test and linear model. We found decreasing area of highly suitable habitat from 0.51% to 0.46%, 0.36% and 0.33%, 0.24% for Prunus africana and 1.13% to 1.02%, 0.77% and 0.76%, 0.60% for Pouteria adolfi-friederici, under RCP 4.5 and RCP 8.5 by 2050 and 2070 respectively. Moist and dry afromontane forests are identified as the most suitable habitat for both species. Overall, our results suggest that climate change can promote dynamic suitable habitat niches under different future climate scenarios. Therefore, biodiversity conservation strategies should take into account habitat suitability dynamics issues and identify where to conserve species before implementing conservation practices.     

Least concern to endangered: Applying climate change projections profoundly influences the extinction risk assessment for wild Arabica coffee

Arabica coffee (Coffea arabica) is a key crop in many tropical countries and globally provides an export value of over US$13 billion per year. Wild Arabica coffee is of fundamental importance for the global coffee sector and of direct importance within Ethiopia, as a source of harvestable income and planting stock. Published studies show that climate change is projected to have a substantial negative influence on the current suitable growing areas for indigenous Arabica in Ethiopia and South Sudan. Here we use all available future projections for the species based on multiple general circulation models (GCMs), emission scenarios, and migration scenarios, to predict changes in Extent of Occurrence (EOO), Area of Occupancy (AOO), and population numbers for wild Arabica coffee. Under climate change our results show that population numbers could reduce by 50% or more (with a few models showing over 80%) by 2088. EOO and AOO are projected to decline by around 30% in many cases. Furthermore, present‐day models compared to the near future (2038), show a reduction for EOO of over 40% (with a few cases over 50%), although EOO should be treated with caution due to its sensitivity to outlying occurrences. When applying these metrics to extinction risk, we show that the determination of generation length is critical. When applying the International Union for Conservation of Nature's Red list of Threatened Species (IUCN Red List) criteria, even with a very conservative generation length of 21 years, wild Arabica coffee is assessed as Threatened with extinction (placed in the Endangered category) under a broad range of climate change projections, if no interventions are made. Importantly, if we do not include climate change in our assessment, Arabica coffee is assessed as Least Concern (not threatened) when applying the IUCN Red List criteria.     

Brucellosis Seropositivity in Animals and Humans in Ethiopia: A Meta-analysis

BackgroundThe objectives of this study were to assess the heterogeneities of estimates and to estimate the seroprevalence of brucellosis in animals and humans in Ethiopia.ConclusionsThe seroprevalence of brucellosis is higher in goats than in other species. Its occurrence is evocative of its importance in the country in general and in the pastoral system in particular. Public awareness creation could reduce the transmission of Brucella spp. from animals to humans and the potential of livestock vaccination as a means of control of brucellosis needs to be assessed.