Trypanosoma brucei Glycogen Synthase Kinase-3, A Target for Anti-Trypanosomal Drug Development: A Public-Private Partnership to Identify Novel Leads

Over 60 million people in sub-Saharan Africa are at risk of infection with the parasite Trypanosoma brucei which causes Human African Trypanosomiasis (HAT), also known as sleeping sickness. The disease results in systemic and neurological disability to its victims. At present, only four drugs are available for treatment of HAT. However, these drugs are expensive, limited in efficacy and are severely toxic, hence the need to develop new therapies. Previously, the short TbruGSK-3 short has been validated as a potential target for developing new drugs against HAT. Because this enzyme has also been pursued as a drug target for other diseases, several inhibitors are available for screening against the parasite enzyme. Here we present the results of screening over 16,000 inhibitors of human GSK-3β (HsGSK-3) from the Pfizer compound collection against TbruGSK-3 short. The resulting active compounds were tested for selectivity versus HsGSK-3β and a panel of human kinases, as well as their ability to inhibit proliferation of the parasite in vitro. We have identified attractive compounds that now form potential starting points for drug discovery against HAT. This is an example of how a tripartite partnership involving pharmaceutical industries, academic institutions and non-government organisations such as WHO TDR, can stimulate research for neglected diseases

Efficient Shoot Organogenesis Using Leaf Disc and Nodal Explants of Passion Fruit (Passiflora edulis Sims) and Genetic Fidelity Assessment Using Sequence-Related Amplified Polymorphism (SRAP) Markers

Passion fruit (Passiflora edulis (Sims)) is currently ranked third among fruit exports from Kenya and has great potential since the demand for both fresh fruit and processed juice is on a continuous increase. Passion fruit production in Kenya is constrained by a lack of healthy, clean planting material, poor seed viability, and low germination rates. To address this, the present study reports an in vitro plant regeneration protocol for passion fruit using leaf disc and nodal explants and genetic fidelity analysis of the regenerated plants. The highest number of shoot regeneration was obtained on Murashige and Skoog (MS) medium supplemented with 2 mg·L−1 6-Benzyl amino purine (BAP) (shoot induction medium). The multiplication of shoots was optimum in MS medium supplemented with 3 mg·L−1 BAP. To eliminate the requirement of an additional step of in vitro rooting, exogenous application of putrescine induced the formation and development of roots on nodal explants. Genetic fidelity analysis of the in vitro regenerated and macropropagated plants with that of the mother plant was carried out by sequence-related amplified polymorphism (SRAP) markers, and monomorphic banding profile for 80% of the regenerants confirmed the genetic uniformity of the in vitro regenerated and macropropagated plants. The in vitro regeneration system developed can be utilized for mass clonal propagation for the economic commercial exploitation of this important tropical fruit

Comparative Analysis Delineates the Transcriptional Resistance Mechanisms for Pod Borer Resistance in the Pigeonpea Wild Relative Cajanus scarabaeoides (L.) Thouars

Insect pests pose a serious threat to global food production. Pod borer (Helicoverpa armigera (Hübner)) is one of the most destructive pests of leguminous crops. The use of host resistance has been an effective, environmentally friendly and sustainable approach for controlling severalagricultural pests. The exploitation of natural variations in crop wild relatives could yield pestresistant crop varieties. In this study, we used a high-throughput transcriptome profiling approach to investigate the defense mechanisms of susceptible cultivated and tolerant wild pigeonpea genotypes against H. armigera infestation. The wild genotype displayed elevated pest-induced gene expression, including the enhanced induction of phytohormone and calcium/calmodulin signaling, transcription factors, plant volatiles and secondary metabolite genes compared to the cultivated control. The biosynthetic and regulatory processes associated with flavonoids, terpenes and glucosinolatesecondary metabolites showed higher accumulations in the wild genotype, suggesting the existence of distinct tolerance mechanisms. This study provides insights into the molecular mechanisms underlying insect resistance in the wild pigeonpea genotype. This information highlights the indispensable role of crop wild relatives as a source of crucial genetic resources that could be important in devising strategies for crop improvement with enhanced pest resistance.<br/

Drought tolerance in transgenic tropical maize (Zea mays L.) by heterologous expression of peroxiredoxin2 gene-XvPrx2

Transformation of a tropical maize inbred genotype (CML144) with the Xerophyta viscosa peroxiredoxin2 (XvPrx2) gene was reported. The protective role of peroxiredoxin2 against the damage resulting from reactive oxygen species (ROS) under dehydration stress was further determined. Successful integration of XvPrx2 gene into maize we achieved and recovered 10 independent transgenic events. Transformation and regeneration frequencies were 12.9 and 31.3%, respectively. Reverse transcription polymerase chain reaction (PCR) revealed the expression of the XvPrx2 gene in transformed plants under dehydration. Stressed transgenic plants had higher relative water content (RWC) as compared to the conventional plants. Recovery irrigation showed higher RWC in transgenics than in conventional plants. Unlike in conventional plants, rapid morphogenic recovery was observed in transgenics within 24 h. Chlorophyll contents decreased faster in conventional plants than in transgenics with prolonged drought. Generally, transgenic plants were more tolerant to dehydration stress than conventional plants. This tolerance may be associated with the over expression of peroxiredoxin2 playing a role in managing ROS generated in plant cells.Keywords: Xerophyta viscosa, reactive oxygen species (ROS), transgenic drought tolerant maize, plant breedin

Kinase selectivity screening.

<p>Compounds were screened in one of two kinase panels at a concentration of 10 µM. The degree of inhibition of each kinase is indicated by shading as follows: white <29% inhibition, light grey 30-49% inhibition, dark grey 50-69% inhibition, black >70% inhibition. Key to compounds: (1) 0181276, (2) CE-160042, (3) 0180532, (4) PF-4903528, (5) PF-4936572, (6) PF-4995633, (7) AG-24290, (8) PF-4279731, (9) CE-317112, (10) PF-1242377, (11) PF-744923, (12) PF-2368935, (13) PF-956933. NT  =  not tested.</p

Modelling of the binding-site residues with putative inhibitors.

<p>Compounds (orange) docked into the catalytic domain of the crystal structure of <i>Hs</i>GSK3 beta in their binding modes. A: CE-317112 shows preference for <i>Hs</i>GSK-3 beta. B: PF-4903528 shows preference for <i>Tbru</i>GSK-3 short. The residues that differ between human and <i>Tbru</i>GSK-3 short are shown in magenta, with only L132M (top centre of the image) directly lining the pocket. Images were created using the Pfizer molecule-modelling package MoViT.</p

GSK-3 Enzyme, Antiparasitic and cytotoxicity testing (values in µM).

<p>Values are a mean of at least 2 replicates. NT  =  not tested due to limited compound availability.</p><p>*Due to limited compound availability, these compounds were only tested at a single concentration of 1 µM and showed >50% inhibition at this concentration.</p

Pasture enclosures increase soil carbon dioxide flux rate in Semiarid Rangeland, Kenya

Abstract Background Pasture enclosures play an important role in rehabilitating the degraded soils and vegetation, and may also influence the emission of key greenhouse gasses (GHGs) from the soil. However, no study in East Africa and in Kenya has conducted direct measurements of GHG fluxes following the restoration of degraded communal grazing lands through the establishment of pasture enclosures. A field experiment was conducted in northwestern Kenya to measure the emission of CO2, CH4 and N2O from soil under two pasture restoration systems; grazing dominated enclosure (GDE) and contractual grazing enclosure (CGE), and in the adjacent open grazing rangeland (OGR) as control. Herbaceous vegetation cover, biomass production, and surface (0–10 cm) soil organic carbon (SOC) were also assessed to determine their relationship with the GHG flux rate. Results Vegetation cover was higher enclosure systems and ranged from 20.7% in OGR to 40.2% in GDE while aboveground biomass increased from 72.0 kg DM ha−1 in OGR to 483.1 and 560.4 kg DM ha−1 in CGE and GDE respectively. The SOC concentration in GDE and CGE increased by an average of 27% relative to OGR and ranged between 4.4 g kg−1 and 6.6 g kg−1. The mean emission rates across the grazing systems were 18.6 μg N m−2 h−1, 50.1 μg C m−2 h−1 and 199.7 mg C m−2 h−1 for N2O, CH4, and CO2, respectively. Soil CO2 emission was considerably higher in GDE and CGE systems than in OGR (P < 0.001). However, non-significantly higher CH4 and N2O emissions were observed in GDE and CGE compared to OGR (P = 0.33 and 0.53 for CH4 and N2O, respectively). Soil moisture exhibited a significant positive relationship with CO2, CH4, and N2O, implying that it is the key factor influencing the flux rate of GHGs in the area. Conclusions The results demonstrated that the establishment of enclosures in tropical rangelands is a valuable intervention for improving pasture production and restoration of surface soil properties. However, a long-term study is required to evaluate the patterns in annual CO2, N2O, CH4 fluxes from soils and determine the ecosystem carbon balance across the pastoral landscape