Cooperation of Secondary Transporters and Sensor Kinases in Transmembrane Signalling: The DctA/DcuS and DcuB/DcuS Sensor Complexes of Escherichia coli.

Many membrane-bound sensor kinases require accessory proteins for function. The review describes functional control of membrane-bound sensors by transporters. The C4-dicarboxylate sensor kinase DcuS requires the aerobic or anaerobic C4-dicarboxylate transporters DctA or DcuB, respectively, for function and forms DctA/DcuS or DcuB/DcuS sensor complexes. Free DcuS is in the permanent (ligand independent) ON state. The DctA/DcuS and DcuB/DcuS complexes, on the other hand, control expression in response to C4-dicarboxylates. In DctA/DcuS, helix 8b of DctA and the PASC domain of DcuS are involved in interaction. The stimulus is perceived by the extracytoplasmic sensor domain (PASP) of DcuS. The signal is transmitted across the membrane by a piston-type movement of TM2 of DcuS which appears to be pulled (by analogy to the homologous citrate sensor CitA) by compaction of PASP after C4-dicarboxylate binding. In the cytoplasm, the signal is perceived by the PASC domain of DcuS. PASC inhibits together with DctA the kinase domain of DcuS which is released after C4-dicarboxylate binding. DcuS exhibits two modes for regulating expression of target genes. At higher C4-dicarboxylate levels, DcuS is part of the DctA/DcuS complex and in the C4-dicarboxylate-responsive form which stimulates expression of target genes in response to the concentration of the C4-dicarboxylates (catabolic use of C4-dicarboxylates, mode I regulation). At limiting C4-dicarboxylate concentrations (≤0.05mM), expression of DctA drops and free DcuS appears. Free DcuS is in the permanent ON state (mode II regulation) and stimulates low level (C4-dicarboxylate independent) DctA synthesis for DctA/DcuS complex formation and anabolic C4-dicarboxylate uptake.

Estimating development rate and thermal requirements of Bactericera cockerelli (Hemiptera: Triozidae) reared on potato and tomato by using linear and nonlinear models.

The temperature-dependent development of tomato psyllid (also called potato psyllid), Bactericera cockerelli (Sulc), was studied in the laboratory at seven constant temperatures (8, 10, 15, 20, 23, 27, and 31°C), 50-60% RH, and a photoperiod of 16:8 (L:D) h on leaves of whole potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.) plants. Developmental time in days for immature stages and total development (egg to adult) on both host species were inversely proportional to temperature between 8 and 27°C but increased at 31°C. One linear and two nonlinear models were fitted to the data. The lower developmental thresholds, calculated using the linear model for egg, total nymph, and total development (from oviposition to adult emergence) were 7.9, 4.2, and 7.1°C (reared on potato) and 7.2, 5.3, and 7.5°C (reared on tomato), respectively. The thermal constant (K) for total development was 358 (reared on potato), and 368 (reared on tomato) degree-days (DD). Two nonlinear models, Briere and Lactin, fit the data well as measured by goodness-of-fit criteria, the residual sum of square (RSS) and Akaike information criterion (AIC). Temperature threshold parameters for these nonlinear models (T(0), T(opt), and T(max)) were estimated for eggs, total nymphal stages, and total development time (egg to adult). The Briere model is highly recommended for the description of temperature-dependent development of tomato psyllid. Results from this study will provide basic information on the biology of tomato psyllid and have potential for the development of predictive models of the seasonal progress of this invasive pest.

Determination of the influence of dispersion pattern of pesticide-resistant individuals on the reliability of resistance estimates using different sampling plans.

Pesticide resistance monitoring includes resistance detection and subsequent documentation/ measurement. Resistance detection would require at least one (≥1) resistant individual(s) to be present in a sample to initiate management strategies. Resistance documentation, on the other hand, would attempt to get an estimate of the entire population (≥90%) of the resistant individuals. A computer simulation model was used to compare the efficiency of simple random and systematic sampling plans to detect resistant individuals and to document their frequencies when the resistant individuals were randomly or patchily distributed. A patchy dispersion pattern of resistant individuals influenced the sampling efficiency of systematic sampling plans while the efficiency of random sampling was independent of such patchiness. When resistant individuals were randomly distributed, sample sizes required to detect at least one resistant individual (resistance detection) with a probability of 0.95 were 300 (1%) and 50 (10% and 20%); whereas, when resistant individuals were patchily distributed, using systematic sampling, sample sizes required for such detection were 6000 (1%), 600 (10%) and 300 (20%). Sample sizes of 900 and 400 would be required to detect ≥90% of resistant individuals (resistance documentation) with a probability of 0.95 when resistant individuals were randomly dispersed and present at a frequency of 10% and 20%, respectively; whereas, when resistant individuals were patchily distributed, using systematic sampling, a sample size of 3000 and 1500, respectively, was necessary. Small sample sizes either underestimated or overestimated the resistance frequency. A simple random sampling plan is, therefore, recommended for insecticide resistance detection and subsequent documentation.

Noninvasive molecular methods to identify live scarab larvae: an example of sympatric pest and nonpest species in New Zealand.

Despite the negative impact that many scarab larvae have on agro-ecosystems, very little attention has been paid to their taxonomy. Their often extremely similar morphological characteristics have probably contributed to this impediment, which has also meant that they are very difficult to identify in the field. Molecular methods can overcome this challenge and are particularly useful for the identification of larvae to enable management of pest species occurring sympatrically with nonpest species. However, the invasive collection of DNA samples for such molecular methods is not compatible with subsequent behavioural, developmental or fitness studies. Two noninvasive DNA sampling and DNA analysis methods suitable for the identification of larvae from closely related scarab species were developed here. Using the frass and larval exuviae as sources of DNA, field-collected larvae of Costelytra zealandica (White) and Costelytra brunneum (Broun) (Scarabaeidae: Melolonthinae) were identified by multiplex PCR based on the difference in size of the resulting PCR products. This study also showed that small quantities of frass can be used reliably even 7 days after excretion. This stability of the DNA is of major importance in ecological studies where timeframes rarely allow daily monitoring. The approach developed here is readily transferable to the study of any holometabolous insect species for which morphological identification of larval stages is difficult.

Forecasting emergence and movement of overwintering hazelnut big bud mites from big buds.

Eriophyoid big bud mites are key pests of hazelnut throughout the world, but they are difficult to control with chemicals or other methods because they are protected inside the bud. The most effective time for control is during the relatively short emergence period which is difficult for growers to predict. The key objectives of this study were to monitor mite emergence from big buds in spring, determine the phenology of mites in relation to tree phenology and weather, and identify the optimum timing for control measures. Mite emergence was found to occur between early and late spring in Canterbury, New Zealand. Mite emergence and movement occurred when daily maximum temperatures were >15 degrees C and when mean temperatures were >9 degrees C, with mite emergence increasing with temperature. The developmental status of new buds during mite emergence was a crucial factor in the infestation of new buds. An accumulated heat sum model (DD), starting at Julian date 152 and using a lower threshold temperature of 6 degrees C, predicted the onset of emergence on two cultivars and at two sites at approximately 172 DD. A regression model based on leaf number, bud length, bud width, DD and Julian date provided a more satisfactory prediction of percent accumulated mite emergence. It is recommended both peak mite emergence and the developmental status of hazelnut buds be used to optimise the time to apply control measures. The optimum time to apply a control was predicted to be before buds measure 0.5 x 0.5 mm (width x length), are enclosed within the axil, and have a rounded tip, or, when 50% accumulated mite emergence has occurred, whichever occurs first.

Prediction of global distribution of insect pest species in relation to climate by using an ecological informatics method.

The aim of this work was to predict the worldwide distribution of two pest species-Ceratitis capitata (Wiedemann), the Mediterranean fruit fly, and Lymantria dispar (L.), the gypsy moth-based on climatic factors. The distribution patterns of insect pests have most often been investigated using classical statistical models or ecoclimatic assessment models such as CLIMEX. In this study, we used an artificial neural network, the multilayer perceptron, trained using the backpropagation algorithm, to model the distribution of each species. The data matrix used to model the distribution of each species was divided into three data sets to (1) develop and train the model, (2) validate the model and prevent over-fitting, and (3) test each model on novel data. The percentage of correct predictions of the global distribution of each species was high for Mediterranean fruit fly for the three data sets giving 95.8, 81.5, and 80.6% correct predictions, respectively, and 96.8, 84.3, and 81.5 for the gypsy moth. Kappa statistics used to test the level of significance of the results were highly significant (in all cases P < 0.0001). A sensitivity analysis applied to each model based on the calculation of the derivatives of each of a large number of input variables showed that the variables that contributed most to explaining the distribution of C. capitata were annual average temperature and annual potential evapotranspiration. For L. dispar, the average minimum temperature and minimum daylength range were the main explanatory variables. The ANN models and methods developed in this study offer powerful additional predictive approaches in invasive species research.

Sublethal effects of esfenvalerate residues on pyrethroid resistant Typhlodromus pyri (Acari: Phytoseiidae) and its prey Panonychus ulmi and Tetranychus urticae (Acari: Tetranychidae).

The effect of residues of esfenvalerate on oviposition of the resistant strain of the predatory mite Typhlodromus pyri and its main prey, European red mite Panonychus ulmi and two-spotted spider mite Tetranychus urticae, were investigated. T. pyri showed a significant linear reduction in oviposition after 24 h in the presence of increasing levels of esfenvalerate residue applied at the field rate. Furthermore, when given a choice, T. pyri preferred to lay eggs on residue-free surfaces. Of the two prey species, only P. ulmi showed significant avoidance of increasing levels of residues of the field rate concentration of esfenvalerate, as measured by runoff mortality, however both P. ulmi and T urticae, when given a choice, showed a preference for esfenvalerate-free surfaces. As with the predatory mite T. pyri, both prey species showed a significant linear reduction of oviposition with increasing esfenvalerate residues and a preference to lay eggs on esfenvalerate-free surfaces. Esfenvalerate residues as high as 15X field rate were not repellent to pyrethroid-resistant T. pyri. The possible effects of these sublethal effects on predator-prey dynamics and implications for integrated mite control programmes in apple orchards are discussed.

Extraarticular external fixation in distal radius fractures pinplacement in osteoporotic bone.

External fixation is a well accepted treatment option in distal radial fractures. The fixator can be used in two different ways: joint bridging or extraarticular. The extraarticular technique presumes that the fracture does not involve the radio-carpal joint and that the distal fragment is broad enough to accommodate two fixator screws. Taking into account that the majority of distal radius fractures occur in elderly female patients the question arises whether osteoporotic bone is an obstacle to extraarticular external fixation. Bone slices of 2mm thickness were cut out of six human cadaver radii with a mean age of 76 years (from 65 to 94 years) in the saggital plane. A radiograph of each slice was digitized and the distribution of gray values measured. It was found that the radiographic density was highest at the palmar side of the distal radius in a triangular area built by the palmar lip of the radius. In this region, even in severe osteoporotic bone, strong trabeculae are visible running parallel to longitudinal axis of the radius. Fixator screws inserted into the distal radial fragment especially in an osteoporotic situation should be securely anchored in the palmar lip of the distal radius.

No evidence for cancer-related CD44 splice variants in primary and metastatic colorectal cancer.

The expression of alternatively spliced CD44 adhesion molecules has been implicated in the pathogenesis and metastasis of colorectal cancer. Using a new set of primers for exon-specific reverse transcription-polymerase chain reaction (RT-PCR) we delineated the exact exon composition of CD44 mRNAs in normal colorectal mucosa, including isolated colonic crypts, in colorectal carcinomas and in their hepatic metastases. In addition, the surface expression of CD44 isoforms was analysed by immunohistochemistry. We identified by RT-PCR eight variant transcripts expressed in colorectal carcinomas and their metastases, but also constitutively in normal colorectal epithelia. In the normal colorectal epithelium, the surface expression of CD44 standard and variant molecules was restricted to proliferating cells at the bottom of the crypts. Despite expression of these transcripts in colorectal cancers and their metastases, monoclonal antibodies specific for standard or variant epitopes encoded by exons v5 and v6 stained only a few neoplastic lesions. These data point to a differentiation-specific CD44 expression and splicing pattern in proliferating colorectal epithelia. However, they do not support a cancer- or metastasis-specific CD44 splicing pattern. Instead, cell surface availability of CD44 epitopes was reduced rather than increased in primary tumours and particularly in liver metastases.

Ethyl nicotinate : A chemical attractant forThrips obscuratus (Thysanoptera: Thripidae) in stonefruit in New Zealand.

Ethyl nicotinate was found to be a potent attractant forThrips obscuratus in peaches and apricots. The male-to-female ratio in traps was 1∶8. The chemical was more attractive than ripe fruit, with peak catches at harvest. Season-long trapping showed the efficiency of the chemical compared to unbaited traps. The chemical remained attractive for at least 2 weeks when 50 µl were placed in open 2-ml vial caps. Various pyralids, geometrids (Lepidoptera), and chironomids (Diptera) were also attracted in low numbers to ethyl nicotinate.