Regenerating Eye Tissues to Preserve and Restore Vision

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Semiochemical-based alternatives to synthetic toxicant insecticides for pollen beetle management

There is an urgent need to develop sustainable pest management systems to protect arable crops in order to replace the current over-reliance on synthetic insecticides. Semiochemicals are insect- or plant-derived chemicals that are used by organisms as information signals. Integrated pest management tools are currently in development that utilise semiochemicals to manipulate the behaviour of pest insects and their natural enemies to provide effective control of pests within the crop. These innovative tools usually require fewer inputs and can involve multiple elements, therefore reducing the likelihood of resistance developing compared with use of synthetic toxicants. We review here the life cycle of the pollen beetle Brassicogethes aeneus (previously known as Meligethes aeneus) which is a pest insect of oilseed rape (Brassica napus) and describe the current knowledge of any behaviour mediated by semiochemicals in this species. We discuss the behavioural processes where semiochemical-based control approaches may be appropriate and consider how these approaches could be incorporated into an integrated pest management strategy for this important arable crop.     

Improvement of cowpea productivity by rhizobial and mycorrhizal inoculation in Burkina Faso

Cowpea is one of the most important food legume crops in Burkina Faso. It is able to associate with arbuscular mycorrhizal fungi (AMF) and rhizobia. This dual symbiosis improves nitrogen and phosphorus nutrient uptake in cowpea. As the application of exotic inoculants frequently lacks positive responses in field experiments, this study set out to select well-adapted native symbiotic rhizobial and AMF strains. Soil samples were collected from six study sites in three different climatic zones of Burkina Faso to investigate their native symbiotic strains. Soil-extraction of native spores led to the identification of four AMF genera (Scutellospora, Gigaspora, Glomus and Entrophospora) by morpho-anatomical characterization. The two most effective cowpea fungal strains were selected after spore isolation from field-collected soils, multiplication on maize roots and inoculation on cowpea seedlings in a greenhouse experiment. Cowpea-nodulating rhizobial strains were trapped in the greenhouse by planting cowpea seeds in collected soil samples and the strains were characterized using molecular methods. This characterization led to the rhizobial isolates being classified in four clusters on the phylogenetic tree (using the Maximum-Likelihood Phylogenies method). All strains belonged to the Bradyrhizobium genus and most of them were included in the B. japonicum branch. Some groups were clearly distinct species already identified and may be new species. The two most effective strains for cowpea yield improvement in the field were selected after cowpea inoculation in a greenhouse experiment. The inoculation design in the field experiment consisted of four single inoculation treatments, either rhizobial or mycorrhizal, along with four dual inoculations, one treatment with chemical fertilizers, and one uninoculated control. The results showed that cowpea productivity was significatively improved by dual inoculation with native rhizobial and mycorrhizal strains, reaching the same level as the application of commonly used chemical fertilizers [Nitrogen, Phosphorus and Potassium fertilizers (NPK)]. In addition, dual inoculation resulted in the highest iron content in cowpea leaves.     

Poly-3-hydroxybutyrate production by washed cells of Alcaligenes eutrophus; purification, characterisation and potential regulatory role of citrate synthase

Washed cells prepared from carbon-limited continuous cultures of Alcaligenes eutrophus synthesised poly-3-hydroxybutyrate (PHB) rapidly when supplied with glucose, dl-lactate or l-lactate. Unlike growing cultures, washed cells excreted significant amounts of pyruvate. The combined rates of PHB production (qPHB) and pyruvate excretion (qPyr) were linearly related to the rate of carbon substrate utilisation (qS), showing that washed cells behaved similarly to growing cultures when corrected for the absence of non-PHB biomass production. The addition of formate (as a potential source of NADH and/or ATP) significantly stimulated both qPHB and qPyr, but slightly decreased qS and substantially decreased the flux of carbon through the tricarboxylic acid cycle (qTCA). Citrate synthase activity of broken cells was inhibited by physiological concentrations of NADH, but not of ATP, in a manner that was not reversible by AMP. Citrate synthase was purified and shown to be a “large” form of the enzyme (M _r 227,000), comprising a single type of subunit (M _r 47,000) as found in several other gram-negative aerobes. The potential role of citrate synthase in the regulation of PHB production via its ability to control carbon flux into the tricarboxylic acid cycle is discussed. Received: 14 March 1997 / Accepted: 9 July 1997     

Zinc efficiency of oilseed rape (t Brassica napus and t B. juncea) genotypes

Twenty five genotypes of oilseed rape (canola and mustard) were tested under varied supply of Zn (+Zn: 2 mg kg^–1 soil, -Zn: no Zn added) in two pot experiments in soil culture to determine the genotypic variation in tolerance to the Zn-deficient conditions, that is, to identify the Zn-efficient genotypes. On the basis of performance of genotypes in pot experiments, ten genotypes were tested in 1995 for their performance under varied supply of Zn (+Zn: 3.5 kg ha^–1, -Zn: no Zn added) on a Zn-deficient field in South Australia.Zn efficiency (ratio of shoot dry matter in -Zn to shoot dry matter in +Zn treatment and expressed in percentage) in pot Experiment 1 varied from 35% for 92-13 to 74% for Siren. Narendra, Dunkeld, Barossa, Oscar and Xinza 2 performed well under -Zn treatment. Zn efficiency in Experiment 2 varied from 32% for Wuyou 1 to 62% for Pusa Bold. Pusa Bold and CSIRO-1(mustard genotypes) were the most efficient in terms of dry matter production among all the oilseed rape genotypes tested. Root dry matter accumulation was significantly higher in Zn-efficient genotypes. Zn efficiency (ratio of seed yield in -Zn to seed yield in +Zn and expressed in percentage) in field experiment varied from 62% for Huashang 2 to 76% for Dunkeld. With few exceptions, the ranking of genotypes in pot and field experiments indicates similarity in their response to Zn deficiency. There looks to be genetic control over Zn concentration in tissues. Zn-efficient genotypes had lower Zn concentration in roots and higher Zn concentration in youngest fully opened leaf blades, indicating a better transport of Zn. This, together with a higher Zn uptake, appears to be the basis of expression of Zn efficiency.     

Numerical comparison of several approximations of the word count distribution in random sequences.

The exact distribution of word counts in random sequences and several approximations have been proposed in the past few years. The exact distribution has no theoretical limit but may require prohibitive computation time. On the other hand, approximate distributions can be rapidly calculated but, in practice, are only accurate under specific conditions. After making a survey of these distributions, we compare them according to both their accuracy and computational cost. Rules are suggested for choosing between Gaussian approximations, compound Poisson approximation, and exact distribution. This work is illustrated with the detection of exceptional words in the phage Lambda genome.     

The Distributed Annotation System

Background  

Currently, most genome annotation is curated by centralized groups with limited resources. Efforts to share annotations transparently among multiple groups have not yet been satisfactory.     

Thresholds of Response in Nest Thermoregulation by Worker Bumble Bees, Bombus bifarius nearcticus (Hymenoptera: Apidae)

Regulation of nest temperature is important to the fitness of eusocial insect colonies. To maintain appropriate conditions for the developing brood, workers must exhibit thermoregulatory responses to ambient temperature. Because nest-mate workers differ in task performance, thermoregulatory behavior provides an opportunity to test threshold of response models for the regulation of division of labor. We found that worker bumble bees ( Bombus bifarius nearcticus ) responded to changes in ambient temperature by altering their rates of performing two tasks – wing fanning and brood cell incubation. At the colony level, the rate of incubating decreased, and the rate of fanning increased, with increasing temperature. Changes in the number of workers performing these tasks were more important to the colony response than changes in workers' task performance rates. At the individual level, workers' lifetime rates of incubation and fanning were positively correlated, and most individuals did not specialize exclusively on either of these temperature-sensitive tasks. However, workers differed in the maximum temperature at which they incubated and in the minimum temperature at which they fanned. More individuals fanned at high and incubated at low temperatures. Most of the workers that began incubating at higher temperatures continued performing this task at lower temperatures, when additional nest-mates became active. The converse was true for fanning behavior. These data are consistent with a threshold of response model for thermoregulatory behavior of B. bifarius workers.     

The disease business

A report on the 'Host-Pathogen Interactions' minisymposium at the first meeting of the European Life Scientist Organization (ELSO), Geneva, Switzerland, September 2-6, 2000.