Mapping Soil Properties of Africa at 250 m Resolution: Random Forests Significantly Improve Current Predictions

80% of arable land in Africa has low soil fertility and suffers from physical soil problems. Additionally, significant amounts of nutrients are lost every year due to unsustainable soil management practices. This is partially the result of insufficient use of soil management knowledge. To help bridge the soil information gap in Africa, the Africa Soil Information Service (AfSIS) project was established in 2008. Over the period 2008–2014, the AfSIS project compiled two point data sets: the Africa Soil Profiles (legacy) database and the AfSIS Sentinel Site database. These data sets contain over 28 thousand sampling locations and represent the most comprehensive soil sample data sets of the African continent to date. Utilizing these point data sets in combination with a large number of covariates, we have generated a series of spatial predictions of soil properties relevant to the agricultural management—organic carbon, pH, sand, silt and clay fractions, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content and exchangeable bases (Ca, K, Mg, Na). We specifically investigate differences between two predictive approaches: random forests and linear regression. Results of 5-fold cross-validation demonstrate that the random forests algorithm consistently outperforms the linear regression algorithm, with average decreases of 15–75% in Root Mean Squared Error (RMSE) across soil properties and depths. Fitting and running random forests models takes an order of magnitude more time and the modelling success is sensitive to artifacts in the input data, but as long as quality-controlled point data are provided, an increase in soil mapping accuracy can be expected. Results also indicate that globally predicted soil classes (USDA Soil Taxonomy, especially Alfisols and Mollisols) help improve continental scale soil property mapping, and are among the most important predictors. This indicates a promising potential for transferring pedological knowledge from data rich countries to countries with limited soil data.     

<Emphasis Type="Italic">In vitro</Emphasis> organogenesis of <Emphasis Type="Italic">Passiflora alata</Emphasis>

Passiflora alata in vitro organogenesis was studied based on explant type, culture medium composition, and incubation conditions. The results indicated that the morphogenic process occurred more efficiently when hypocotyl segment-derived explants were cultured in media supplemented with cytokinin and AgNO₃ incubated under a 16-h photoperiod. The shoot bud elongation and plant development were obtained by transferring the material to MSM culture medium supplemented with GA₃ and incubated in flasks with vented lids. Histological analyses of the process revealed that the difficulties in obtaining plants could be related to the development of protuberances and leaf primordia structures, which did not contain shoot apical meristem. Roots developed easily by transferring elongated shoots to 1/2 MSM culture medium. Plant acclimatization occurred successfully, and somaclonal variation was not visually detected. The efficiency of this organogenesis protocol will be evaluated for genetic transformation of this species to obtain transgenic plants expressing genes that can influence the resistance to Cowpea aphid borne mosaic virus.     

Ground use by northern muriquis (Brachyteles hypoxanthus)

Many arboreal primates descend to the ground, a custom that may occur more frequently in disturbed habitats, and in the presence of researchers to whom the primates are habituated. In this paper, we describe opportunistic observations of ground use in two groups of northern muriquis (Brachyteles hypoxanthus) at the RPPN Feliciano Miguel Abdala, Minas Gerais, Brazil. Members of both groups were observed drinking, resting, feeding, playing, and traveling on the ground to different degrees, and variation in the levels of habituation of the two groups may be responsible for the differences in the distribution of their terrestrial activities. The potential increase in vulnerability to predation or disease owing to ground use has implications for the conservation of this critically endangered species.     

Wnt/beta-catenin pathway activation and myogenic differentiation are induced by cholesterol depletion

Myogenic differentiation is a multistep process that begins with the commitment of mononucleated precursors that withdraw from cell cycle. These myoblasts elongate while aligning to each other, guided by the recognition between their membranes. This step is followed by cell fusion and the formation of long and striated multinucleated myotubes. We have recently shown that cholesterol depletion by methyl-beta-cyclodextrin (MbetaCD) induces myogenic differentiation by enhancing myoblast recognition and fusion. Here, we further studied the signaling pathways responsible for early steps of myogenesis. As it is known that Wnt plays a role in muscle differentiation, we used the chemical MbetaCD to deplete membrane cholesterol and investigate the involvement of the Wnt/beta-catenin pathway during myogenesis. We show that cholesterol depletion promoted a significant increase in expression of beta-catenin, its nuclear translocation and activation of the Wnt pathway. Moreover, we show that the activation of the Wnt pathway after cholesterol depletion can be inhibited by the soluble protein Frzb-1. Our data suggest that membrane cholesterol is involved in Wnt/beta-catenin signaling in the early steps of myogenic differentiation.     

Dispersion patterns of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in citrus orchards in southeast Brazil

We studied the dispersion patterns of the exotic endoparasitoid, Diachasmimorpha longicaudata (Ahsmed) (Hymenoptera: Braconidae), in 1999 (summer) and in 2000 (winter) in a citrus orchard in southeast Brazil. Different population densities of D. longicaudata were released in the centre of the orchard, and their dispersion was determined by using yellow, sticky, rectangular traps, placed in various distances and heights around the release point. Our results suggest that during summer, climatic conditions did not affect dispersion. However, in winter, dispersion rates were positively affected by temperature, and negatively by rainfall. Both estimated dispersal distance and surface were higher in summer than in winter for all release densities. Dispersion peaked at 2000 parasitoids ha^?1 in summer and 8000 parasitoids ha^?1 in winter. The importance of our results for the biological control of fruit flies by augmented or innoculative releases of D. longicaudata in southeast Brazil is discussed.     

Structural analysis of Canavalia maritima and Canavalia gladiata lectins complexed with different dimannosides: new insights into the understanding of the structure-biological activity relationship in legume lectins

Plant lectins, especially those purified from species of the Leguminosae family, represent the best studied group of carbohydrate-binding proteins. The legume lectins from Diocleinae subtribe are highly similar proteins that present significant differences in the potency/efficacy of their biological activities. The structural studies of the interactions between lectins and sugars may clarify the origin of the distinct biological activities observed in this high similar class of proteins. In this way, this work presents a crystallographic study of the ConM and CGL (agglutinins from Canavalia maritima and Canavalia gladiata, respectively) in the following complexes: ConM/CGL:Man(alpha1-2)Man(alpha1-O)Me, ConM/CGL:Man(alpha1-3)Man(alpha1-O)Me and ConM/CGL:Man(alpha1-4)Man(alpha1-O)Me, which crystallized in different conditions and space group from the native proteins. The structures were solved by molecular replacement, presenting satisfactory values for R(factor) and R(free). Comparisons between ConM, CGL and ConA (Canavalia ensiformis lectin) binding mode with the dimannosides in subject, presented different interactions patterns, which may account for a structural explanation of the distincts biological properties observed in the lectins of Diocleinae subtribe.     

Chromanones with leishmanicidal activity from Calea uniflora

The dichloromethane extract of Calea uniflora afforded a mixture of two novel chromanones, uniflorol-A (1) and uniflorol-B (2), and one known chromanone, 2,2-dimethyl-6-(1-hydroxyethyl)-chroman-4-one (3). The structures of these compounds were determined by spectroscopic methods. Biological activity of the compounds against Leishmania major promastigotes was evaluated. Mixture of the novel chromanones 1 and 2 showed significant growth inhibition of the parasite in the micrograms per milliliter range.