Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

Microbial control of flies in latrines in Dares Salaam with aBacillus thuringiensis (serotype 1) preparation,Muscabac

Summary Muscabac, aBacillus thuringiensis preparation containing exotoxin, was tested for its ability to control flies in latrines in a tropical environment.Chrysomyia sp. andEristalis sp., both species of medical importance, were the most common flies in the latrines. Both species were sensitive to treatment withB. thuringiensis. Reasonably good, lasting control was obtained in many latrines, but control was poor or partial in some, particularly those in which fresh faeces accumulated rapidly. A more frequent treatment with the bacteria would probably be more effective. An important result from a practical point of view was that the cell mass alone was at least as effective as the whole bacterial culture preparation (i.e. Muscabac) which contains the exotoxin. Microbiological examination showed that the bacterium grew well in many latrines, producing enough exotoxin to kill the fly larvae and give a long lasting control effect.

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Control microbiano en letrinas de Dar es Salaam con Muscabac, una preparación de Bacillus thuringiensis (serotipo 1)

Resumen Se ha estudiado la capacidad del Muscabac, una preparación deBacillus thuringiensis que contiene una exotoxina, para controlar las poblaciones de moscas en las letrinas de ambientes tropicales. La moscas más comunes en las letrinas fueronChrysomyia sp. yEristalis, sp., ambas de interés sanitario. Las dos especies fueron sensibles al tratamiento conB. thuringiensis. En muchas letrinas se obtuvo un efecto remanente razonablemente bueno, pero en otras, el control fué malo o parcial, particularmente en aquellas letrinas en las que los excrementos recientes se acumulaban rápidamente. Un tratamiento bacteriano más frecuente probablemente sería más efectivo. Un resultado importante desde el punto de vista práctico fué que el tratamiento con la masa de células fué al menos tan efectivo como una preparación con el cultivo bacteriano completo (i.e. Muscabac) que contenía la exotoxina. El exámen microbiológico mostró que la bacteria creció bien en muchas letrinas produciendo toxina suficiente para matar a las larvas de mosca y manteniendo el efecto controlante durante largo tiempo.

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Contrôle microbiologique des mouches dans les latrines de Dar es Salam par une préparation (Muscabac) de Bacillus thuringiensis (sérotype 1)

Résumé Une préparation (Muscabac) deBacillus thuringiensis contenant l'exotoxine a été essayée pour son aptitude à contrôler les mouches dans des latrines en région tropicale.Chrysogenia sp. etEristalis sp., espèces d'importance médicale, sont les mouches les plus fréquentes dans ces latrines. Les deux espèces sont sensibles à un traitement parB. thuringiensis. Le plus souvent, on obtient ainsi un contrôle raisonnablement satisfaisant et durable, mais les résultats sont faibles ou partiels dans certains cas, notamment lorsque les fèces s'accumulent rapidement. Du point de vue pratique, un résultat important est que les cellules bactériennes seules sont au moins aussi efficaces que les préparations bactériennes totales contenant, comme le Muscabac, l'exotoxine. Les examens microbiologiques montrent que la bactérie se développe bien dans beaucoup de latrines et produit suffisamment de toxine pour tuer les larves de mouches et pour assurer un contrôle de longue durée.

     

Genetic differences among wild oat lines in potassium uptake and growth in relation to potassium supply

Summary Short-term (10 min) K⁺ (⁸⁶Rb) influxes (ϕK _oc ⁺ ), rates of net K⁺ uptake (ϕK _net ⁺ ) and growth in relation to K⁺ supply were studied in genetically pure lines of wild oat. The wild oat lines employed in this study showed substantial differences in these trais. ϕK _oc ⁺ was higher in the AN lines (AN5 1, AN 474) than CS 40 and SH lines (SH 319, SH 430) in plants grown under both low and high K⁺ conditions. Kinetic constants V_max and K_m for ϕK _oc ⁺ , of selected lines and the rates of change of these constants with root K⁺ concentration ([K⁺]) showed that ϕK _oc ⁺ in AN 51 was consistently higher than in CS 40 and SH 319. ϕK _net ⁺ was also generally higher in AN 51. ϕK _net ⁺ (at different growth stages), unlike ϕK _oc ⁺ , failed to correlate with root [K⁺]; ϕK _net ⁺ values were low during the first two weeks despite lower root [K⁺]. CS 40 showed the highest utilization efficiency, produced the largest amount of biomass, absorbed most K⁺ and flowered earliest (by day 30). AN 51 had not produced flowers at day 42.     

Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

The ParaSight-F test: a simple rapid manual dipstick test to detect Plasmodium falciparum infection

A rapid diagnostic for Plasmodium falciparum based on an antigen capture has been incorporated in a simple, easily interpreted dipstick by Becton Dickinson Advanced Diagnostics. In this article Clive Shiff, Japhet Minjas and Zul Premji discuss its evaluation in rural Tanzania and the implications of such a test in handling malaria cases under field conditions.     

BRCT domains: Easy as one,two, three

BRCA1 C-terminal (BRCT) domains are integral signaling modules in the DNA damage response (DDR). Aside from their established roles as phospho-peptide binding modules, BRCT domains have been implicated in phosphorylation-independent protein interactions, DNA binding and poly(ADP-ribose) (PAR) binding. These numerous functions can be attributed to the diversity in BRCT domain structure and architecture, where domains can exist as isolated single domains or assemble into higher order homo- or hetero-domain complexes. In this review, we incorporate recent structural and biochemical studies to demonstrate how structural features allow single and tandem BRCT domains to attain a high degree of functional diversity.Key words: BRCT domain, DNA repair, phosphorylation, phospho-peptide interaction, protein interaction, DNA binding, DNA damage response     

Metabolic footprint of epiphytic bacteria on Arabidopsis thaliana leaves

The phyllosphere, which is defined as the parts of terrestrial plants above the ground, is a large habitat for different microorganisms that show a high extent of adaption to their environment. A number of hypotheses were generated by culture-independent functional genomics studies to explain the competitiveness of specialized bacteria in the phyllosphere. In contrast, in situ data at the metabolome level as a function of bacterial colonization are lacking. Here, we aimed to obtain new insights into the metabolic interplay between host and epiphytes upon colonization of Arabidopsis thaliana leaves in a controlled laboratory setting using environmental metabolomics approaches. Quantitative nuclear magnetic resonance (NMR) and imaging high-resolution mass spectrometry (IMS) methods were used to identify Arabidopsis leaf surface compounds and their possible involvement in the epiphytic lifestyle by relative changes in compound pools. The dominant carbohydrates on the leaf surfaces were sucrose, fructose and glucose. These sugars were significantly and specifically altered after epiphytic leaf colonization by the organoheterotroph Sphingomonas melonis or the phytopathogen Pseudomonas syringae pv. tomato, but only to a minor extent by the methylotroph Methylobacterium extorquens. In addition to carbohydrates, IMS revealed surprising alterations in arginine metabolism and phytoalexin biosynthesis that were dependent on the presence of bacteria, which might reflect the consequences of bacterial activity and the recognition of not only pathogens but also commensals by the plant. These results highlight the power of environmental metabolomics to aid in elucidating the molecular basis underlying plant–epiphyte interactions in situ.