Dawit Abate

Genetic adaptation to high altitude in the Ethiopian highlands

BackgroundGenomic analysis of high-altitude populations residing in the Andes and Tibet has revealed several candidate loci for involvement in high-altitude adaptation, a subset of which have also been shown to be associated with hemoglobin levels, including EPAS1, EGLN1, and PPARA, which play a role in the HIF-1 pathway. Here, we have extended this work to high- and low-altitude populations living in Ethiopia, for which we have measured hemoglobin levels. We genotyped the Illumina 1M SNP array and employed several genome-wide scans for selection and targeted association with hemoglobin levels to identify genes that play a role in adaptation to high altitude.ResultsWe have identified a set of candidate genes for positive selection in our high-altitude population sample, demonstrated significantly different hemoglobin levels between high- and low-altitude Ethiopians and have identified a subset of candidate genes for selection, several of which also show suggestive associations with hemoglobin levels.ConclusionsWe highlight several candidate genes for involvement in high-altitude adaptation in Ethiopia, including CBARA1, VAV3, ARNT2 and THRB. Although most of these genes have not been identified in previous studies of high-altitude Tibetan or Andean population samples, two of these genes (THRB and ARNT2) play a role in the HIF-1 pathway, a pathway implicated in previous work reported in Tibetan and Andean studies. These combined results suggest that adaptation to high altitude arose independently due to convergent evolution in high-altitude Amhara populations in Ethiopia.

Cytochalasins and phytotoxins from the fungus Xylaria obovata

The new metabolites xylobovatin, 19,20-epoxycytochalasin C, deacetyl-19,20-epoxy-cytochalasin C, xylobovide and 4,6,10,12-tridecatetraene-2,8-diol, and the known clonostachydiol and phaseolinon were isolated from the culture broth of the Ethiopian fungus Xylaria obovata. While the cytochalasins are cytotoxins, clonostachydiol is an anthelmintic, and phaseolinon and xylobovide show phytotoxic effects. The formation of these metabolites was studied and the more oxidized cytochalasins were found to be formed late in the fermentation process on moist sterile rice.

Antioxidant property of edible mushrooms collected from Ethiopia.

Two cultivated (P. ostreatus and L. edodes) and five wild (L. sulphureus, A. campestris, T. clypeatus, T. microcarpus and T. letestui) edible mushrooms were analyzed for their antioxidant activities, total phenolics, total flavonoids, phenolic profile and ergothioneine content. Results showed that A. campestris had the greatest antioxidant activity in all assays with lower EC50 (mg/ml) values of 1.4, 3.6 and 0.035 for scavenging, reducing and chelating activities, respectively. To correlate well with activities, A. campestris also exhibited greater total phenolics and total flavonoids content of 14.6 mg GAE/g and 1.97 mg CE/g, respectively. The maximum concentration (μg/g) of the individual phenolic compounds were 7.80 (P. ostreatus) for caffeic acid, 4.55 (T. letestui) for chlorogenic acid, 15.8 (T. microcarpus) for p-coumaric acid, 20.3 (A. campestris) for ferulic acid, 561.9 (A. campestris) for gallic acid, 38.7 (A. campestris) for p-hydroxybenzoic acid and 7.08 (A. campestris) for myricetin. All samples tested contained different amounts of ergothioneine ranging from 0.08 (L. sulphureus) to 3.78 (P. ostreatus) mg/g in dry weight.

Two new cytotoxic cytochalasins from Xylaria obovata

Abstract Two new cytotoxic cytochalasins were isolated by brine shrimp bioassay-guided fractionation from a culture of the wood inhabiting fungus, Xylaria obovata . Their structures were determined as 19,20-epoxycytochalasin Q ( 1 ) and its deacetyl analog 2 by the application of spectroscopic techniques and chemical correlation with cytochalasin R. Acetylation of 2 yielded 1 . Both 1 and 2 were cytotoxic but were found to be inactive in an HIV-protease inhibitory assay and a mechanism-based DNA damaging yeast assay.

Global diversity and taxonomy of the Inonotus linteus complex (Hymenochaetales, Basidiomycota): Sanghuangporus gen. nov.,Tropicoporus excentrodendri and T. guanacastensis gen. et spp. nov., and 17 new combinations

Although Inonotus linteus complex is placed in the genus Inonotus, its perennial basidiocarps with a dimitic hyphal system, at least in the trama, distinguish the complex from other species in the genus, which have an annual habit and a monomitic hyphal system. The species number of Inonotus linteus complex has been increased in China and tropical America in recent publications. However, whether species in this complex belong to Inonotus has not specifically been addressed. To explore the phylogenetic placement of species of Inonotus linteus complex, we performed a comprehensive study using morphological and phylogenetic data based on global samples. nLSU (53 with 13 new) and ITS (70 with 18 new) datasets were used to produce the phylogenetic results. Taking into consideration the phylogenies inferred from the nLSU and ITS datasets, Inonotus is a polyphyletic genus comprising at least three clades. Clade A, the core Inonotus clade, contains the generic type, Inonotus hispidus, while Clades B and C comprise species from the Inonotus linteus complex. Morphological and phylogenetic evidence indicates that Clades B and C are new genera, and Sanghuangporus and Tropicoporus are introduced in this study. Ten species are transferred to Sanghuangporus and seven to Tropicoporus. Tropicoporus excentrodendri and T. guanacastensis spp. nov. are described, and their distinctive characters are discussed. Keys to the two new genera and the Inonotus sensu stricto, and to species of each new genus are provided.

Curvupallides, a new class of alkaloids from the fungus Curvularia pallescens

Abstract Three alkaloids with a novel skeleton, named curvupallides A, B and C, are described from the phytopathogenic fungus Curvularia pallescens. They possess an unusual α,β-unsaturated ene-amide γ-lactam. Curvupallides are produced - together with phytotoxic spirostaphylotrichines showing structural similarities with them - only under limitation of nitrogen in submerse culture. Their structure were determined using various NMR techniques and MSMS. They displayed no phytotoxic activity so their ecological function could not be determined.

Larvicidal efficacy ofBacillus thuringiensis var. israelensis andBacillus sphaericus onAnopheles arabiensis in Ethiopia

The second instar larvae of the malaria vector mosquito,Anopheles arabiensis,were more susceptible to Bacillus thuringiensis var. israelensis (IPS-82) and B. sphaericus (SPH-88) than the third instar larvae. The LC50 values were 1.0 ΜgI-1 and 1.8 ΜgI-1 for IPS-82 against second and third instar larvae respectively, after 48 h of exposure. The LC50 values for SPH-88 were 3.6 Μg {siI-1} against the second instar larvae and 7.6 ΜgI-1 against the third instar larvae of An. arabiensis. The larvicidal efficacy of SPH-88 was significantly less than IPS-82. The potential of IPS-82 for the control of An. arabiensis in malaria endemic areas is promising.

Characterization of Pectinase from Bacillus subtilis Strain Btk 27 and Its Potential Application in Removal of Mucilage from Coffee Beans

The demand for enzymes in the global market is projected to rise at a fast pace in recent years. There has been a great increase in industrial applications of pectinase owing to their significant biotechnological uses. For applying enzymes at industrial scale primary it is important to know the features of the enzyme. Thus, this study was undertaken with aims of characterizing the pectinase enzyme from Bacillus subtilis strain Btk27 and proving its potential application in demucilisation of coffee. In this study, the maximum pectinase activity was achieved at pH 7.5 and 50°C. Also, the enzyme activity was found stimulated with Mg2+ and Ca2+ metal ions. Moreover, it was stable on EDTA, Trixton-100, Tween 80, and Tween 20. Since Bacillus subtilis strain Btk27 was stable in most surfactants and inhibitors it could be applicable in various industries whenever pectin degradation is needed. The enzyme Km and Vmax values were identified as 1.879 mg/ml and 149.6 U, respectively. The potential application of the enzyme for coffee processing was studied, and it is found that complete removal of mucilage from coffee beans within 24 hours of treatment indicates the potential application in coffee processing.

Relation of protease production to nematode-degrading ability of two Arthrobotrys spp.

A comparison of the nematode-destroying capability of two nematophagous Arthrobotrys spp. (coded ART-1 and ART-2), isolated from soil samples, showed that ART-1 (LD50=290conidia/ml) was more efficient than ART-2 (LD50=725conidia/ml). The two isolates produce extracellular proteases in liquid culture. The proteases from both isolates had a temperature optimum of 50°C. The optimum pH for protease activity was in the range of 7.5–8 for ART-1 and 7.5–9 for ART-2. ART-1 produced more protease activity (13.3±0.72U/ml) than ART-2 (10.9±0.375U/ml). The proteases from ART-1 were more efficient in degrading nematodes than those of ART-2 by virtue of being produced in a larger quantity. We suggest that the difference in the nematode-destroying capability between the two strains is solely the result of the difference in the amount of extracellular proteases they produce.

Agaricus campestris in upland Ethiopia

Agaricus campestris L.ex Fr., provides a large biomass on grazing fields on the Ethiopian highlands and its growth relationship with cattle and horse dung makes it of interest.