Enhancing the fish production potential of Lake Victoria papyrus wetlands,Kenya, using seasonal flood-dependent ponds

We present the findings of a participatory experiment on integrated aquaculture-agriculture systems (Fingerponds) at the Lake Victoria wetlands, Kenya. Fingerponds are flood-based lacustrine or floodplain wetland fishponds. The aim of the study was to explore, within a wetland/floodplain interface environment, the potential of semi-intensive fish production to enhance the wetland fishery and protect the natural ecosystem from wide-scale, destructive encroachment. The ponds were stocked naturally by flood water. After flood recession, livestock manure was added to the ponds and the effects of manuring on water and sediment quality and fish yields were studied. Manuring had positive effects on the nitrogen, phosphorous and chlorophyll a concentrations of the pond water. Regression analysis results indicated that site, manuring and environmental and climatic variables explained 58–70% of the variation in dissolved nitrogen and phosphorous, and 71% of the variation in chorophyll a. Manuring enhanced the total phosphorus concentration in the sediment but it only had marginal effects on total nitrogen. Although the net fish yields were highly variable between sites and seasons, ranging from 402 to 1069 kg ha⁻¹, the data showed that manuring was advantageous. The duration of the culture period, site variability and manuring explained 82% of the variation in fish yields. We conclude that Fingerponds fertilized with livestock manure from abutting riparian subsistence agriculture can improve fish production, enhance food diversity and security and contribute to more efficient use of papyrus wetlands for food production. This in turn may reduce large-scale conversion of wetlands to agriculture.     

An enriched structural kinase database to enable kinome‐wide structure‐based analyses and drug discovery

The development of a kinase structural database, the kinase knowledge base (KKB), is described. It covers all human kinase domain structures that have been deposited in the Protein Data Bank. All structures are renumbered using a common scheme, which enables efficient cross‐comparisons and multiple queries of interest to the kinase field. The common numbering scheme is also used to automatically annotate conserved residues and motifs, and conformationally classify the structures based on the DFG‐loop and Helix C. Analyses of residue conservation in the ATP binding site using the full human‐kinome–sequence alignment lead to the identification of a conserved hydrogen bond between the hinge region backbone and a glycine in the specificity surface. Furthermore, 90% of kinases are found to have at least one stabilizing interaction for the hinge region, which has not been described before.     

Fungal entomopathogens in the rhizosphere

The ecology of fungal entomopathogens in the rhizosphere is an understudied area of insect pathology. The rhizosphere is the region of soil in which the release of root exudates influences the soil microbiota, and may provide a favorable environment for fungal entomopathogens. The objective of this review is to bring together the relatively scant data available to date on the subject of fungal entomopathogens colonizing the rhizosphere and to highlight the importance of these findings. Gaining a better understanding of the ecology of fungal entomopathogens in the rhizosphere will help in the development of successful microbial control strategies against root-feeding insect pests.     

Ring-substituted 11-oxo-11H-indeno[1,2-b]quinoline-6-carboxamides with similar patterns of cytotoxicity to the dual topo I/II inhibitor DACA

A series of ring-substituted analogues of the topoisomerase inhibitor 11-oxo-11H-indeno[1,2-b]quinoline-6-carboxamides was prepared and evaluated. The compounds were prepared by Pfitzinger reaction of the appropriate isatin-7-carboxylic acids and 1-indanones, followed by selective thermal decarboxylation of the resulting tetracyclic diacids, subsequent oxidation of the methylene group with alkaline permanganate under carefully controlled conditions, and 1,1'-carbonyldiimidazole-induced amidation. The compounds were evaluated in a panel of cell lines in culture. The largest increases in cytotoxicity (five to tenfold) were shown by 4-substituted analogues, with the 4-Cl derivative having an IC₅₀ of 8 nM against the Lewis lung carcinoma.     

An investigation into the involvement of defense signaling pathways in components of the nonhost resistance of Arabidopsis thaliana to rust fungi also reveals a model system for studying rust fungal compatibility

Seventeen accessions of Arabidopsis thaliana inoculated with the cowpea rust fungus Uromyces vignae exhibited a variety of expressions of nonhost resistance, although infection hypha growth typically ceased before the formation of the first haustorium, except in Ws-0. Compared with wild-type plants, there was no increased fungal growth in ndr1 or eds1 mutants defective in two of the signal cascades regulated by the major class of Arabidopsis host resistance genes. However, in the Col-0 background, infection hyphae of U. vignae and two other rust fungi were longer in sid2 mutants defective in an enzyme that synthesizes salicylic acid (SA), in npr1 mutants deficient in a regulator of the expression of SA-dependent pathogenesis related (PR) genes, and in NahG plants containing a bacterial salicylate hydroxylase. Infection hyphae of U. vignae and U. appendiculatus but not of Puccinia helianthi were also longer in jar1 mutants, which are defective in the jasmonic acid defense signaling pathway. Nevertheless, haustorium formation increased only for the Uromyces spp. and only in sid2 mutants or NahG plants. Rather than the hypersensitive cell death that usually accompanies haustorium formation in nonhost plants, Arabidopsis typically encased haustoria in calloselike material. Growing fungal colonies of both Uromyces spp., indicative of a successful biotrophic relationship between plant and fungus, formed in NahG plants, but only U. vignae formed growing colonies in the sid2 mutants and cycloheximide-treated wild-type plants. Growing colonies did not develop in NahG tobacco or tomato plants. These data suggest that nonhost resistance of Arabidopsis to rust fungi primarily involves the restriction of infection hypha growth as a result of defense gene expression. However, there is a subsequent involvement of SA but not SA-dependent PR genes in preventing the Uromyces spp. from forming the first haustorium and establishing a sufficient biotrophic relationship to support further fungal growth. The U. vignae-Arabidopsis combination could allow the application of the powerful genetic capabilities of this model plant to the study of compatibility as well as nonhost resistance to rust fungi.     

Sequestration of dietary alkaloids by the spongivorous marine mollusc Tylodina perversa

Specimens of the spongivorous Mediterranean opisthobranch Tylodina perversa that had been collected while feeding on Aplysina acerophoba were shown to sequester the brominated isoxazoline alkaloids of their prey. Alkaloids were stored in the hepatopancreas, mantle tissues, and egg masses in an organ-specific manner. Surprisingly, the known sponge alkaloid aerothionin which is found only in A. cavernicola but not in A. aerophoba was also among the metabolites identified in wild caught specimens of T. perversa as well as in opisthobranchs with a documented feeding history on A. aerophoba. Mollusc derived aerothionin is postulated to be derived from a previous feeding encounter with A. cavernicola as T. perversa was found to freely feed on both Aplysina sponges in aquarium bioassays. The possible ecological significance of alkaloid sequestration by T. perversa is still unknown.     

Cyberkelp: an integrative approach to the modelling of flexible organisms

Biomechanical models come in a variety of forms: conceptual models; physical models; and mathematical models (both of the sort written down on paper and the sort carried out on computers). There are model structures (such as insect flight muscle and the tendons of rats' tails), model organisms (such as the flying insect, Manduca sexta), even model systems of organisms (such as the communities that live on wave-swept rocky shores). These different types of models are typically employed separately, but their value often can be enhanced if their insights are integrated. In this brief report we explore a particular example of such integration among models, as applied to flexible marine algae. A conceptual model serves as a template for the construction of a mathematical model of a model species of giant kelp, and the validity of this numerical model is tested using physical models. The validated mathematical model is then used in conjunction with a computer-controlled tensile testing apparatus to simulate the loading regime placed on algal materials. The resulting information can be used to create a more precise mathematical model.