Ecologically sustainable chemical recommendations for agricultural pest control?

Effective pest control remains an essential part of food production, and it is provided both by chemicals and by natural enemies within agricultural ecosystems. These methods of control are often in conflict because of the negative impact of chemicals on natural enemies. There are already well-established approaches such as those provided by the International Organization for Biological and Integrated Control-Pesticides and Beneficial Organisms for testing, collecting, and publishing information on responses of natural enemies to chemicals based on laboratory responses of specific organisms; however, these tests do not assess the cumulative impact of chemical inputs across an entire season or consider impacts on the complex communities of natural enemies that can provide effective pest control on a farm. Here, we explore the potential of different approaches for assessing the impact of chemicals on agricultural ecosystems and we propose a simple metric for sustainable chemical use on farms that minimizes overall impact on beneficial groups. We suggest ways in which the effectiveness of metrics can be extended to include persistence and habitat features. Such metrics can assist farmers in developing targets for sustainable chemical use as demonstrated in the viticultural industry.     

Structural–functional insights of single and multi-domain Capsicum annuum protease inhibitors

Pin-II protease inhibitors (PIs) are the focus of research interest because of their large structural–functional diversity and relevance in plant defense. Two representative Capsicum annuum PI genes (CanPI-15 and -7) comprising one and four inhibitory repeat domains, respectively, were expressed and recombinant proteins were characterized. β-Sheet and unordered structure was found predominant in CanPI-15 while -7 also displayed the signatures of polyproline fold, as revealed by circular dichroism studies. Inhibition kinetics against bovine trypsin indicated three times higher potency of CanPI-7 (K_i ～ 57 μM) than -15 (～184 μM). Activity and structural stability of these CanPIs were revealed under various conditions of pH, temperature and denaturing agent. Structure prediction, docking studies with proteases and mass spectroscopy revealed the organization of multiple reactive site loops of multi domain PIs in space as well as the steric hindrances imposed while binding to proteases due to their close proximity.     

Macrophage fusion: are somatic and cancer cells possible partners?

The fusion of cells is a fundamental biological event that plays a central role in a variety of developmental and homeostatic processes. Macrophages are present in all tissues and can initiate interaction and fusion. The putative macrophage-fusion machinery is still poorly understood, but some of its components have been identified. Macrophages recognize each other as < self > in order to fuse but some essential questions remain: do macrophages fuse with somatic cells to repair tissues and organs? Do macrophages fuse with tumor cells to trigger metastasis? Agnès Vignery discusses these novel and challenging ideas in this review.     

Macrophage fusion: are somatic and cancer cells possible partners?

Macrophages are present in all tissues and can fuse with themselves to differentiate into multinucleate osteoclasts or giant cells that play a central role in osteoporosis and chronic inflammatory diseases, respectively. Yet, the mechanism by which they fuse remains uncharacterized. The macrophage fusion receptor (MFR) and its ligand CD47 might mediate homotypic fusion of macrophages and allow for their recognition as 'self' before fusion. Although a novel process and controversial idea, macrophages might exploit a similar mechanism for fusion with somatic cells or tumor cells, with resultant organ repair or metastasis, respectively. Hence, macrophages might be the 'double-edged swords' of tissues.     

Hybrid larch heterosis: for which traits and under which genetic control?

RCD1 is a member of the plant-specific SRO protein family. Several SRO genes have been functionally identified in the regulation of abiotic stresses in Arabidopsis and other plant species. However, the function of SROs is largely unknown in apple (Malus×domestica). In this study, six MdSRO-encoding genes were isolated, categorized into two types and mapped to six chromosomes. The phylogenetic analysis demonstrated that the sequences of the AtSRO and MdSRO proteins are highly conserved. Subsequently, expression analysis showed that MdSRO genes had different expression profiles in different tissues and in response to various stresses. Finally, MdRCD1 was isolated for functional identification. The results showed that resistance to oxidation stress in apple calli was enhanced by MdRCD1 overexpression and weakened by MdRCD1 suppression. MdRCD1 also played a crucial role in the regulation of ROS homeostasis in transgenic apple calli and Arabidopsis. Ectopic expression of MdRCD1 significantly enhanced resistance to salt and oxidative stresses in transgenic lines. In addition, MdRCD1 also enhanced drought tolerance due to its influence on stomatal opening. Based on these results, we conclude that MdRCD1 is an important regulator in abiotic stress response.

     

Zn- and Cu-thioneins: a functional classification for metallothioneins?

This report intends to provide the reader with a deeper insight in the chemical, and extensively biological, characteristics of the metallothionein (MT) system. We have devoted nearly 20 years to the study of MTs and this has allowed us to form what we believe is a more complete picture of this peculiar family of metalloproteins. At the beginning of the 1990s, the landscape of this field was quite different from the overall picture we have now. Many researchers have contributed to the readjustment of this part of scientific knowledge. In our case, we implemented a unified method for obtaining MTs, for characterizing their metal-binding features, and for applying a unified research rationale. All this has helped to enlarge the initial picture that was mainly dominated by mammalian MT1/MT2 and yeast Cup1, by introducing approximately 20 new MTs. It has also allowed some characteristics to be clarified and examined in more detail, such as the cooperativity or the coexistence of multiple species in the metal-substitution reactions, the availability of Ag(I) or Cd(II) for use as respective probes for the Cu(I) and Zn(II) binding sites, the participation of chloride or sulfide ligands in the metal coordination spheres, and the feasibility of using in vitro data as representative of in vivo scenarios. Overall, the results yield enough data to consider new criteria for a proposal of classification of MTs based on MT metal-binding features, which complements the previous classifications, and that can shed light on the still controversial physiological functions of this peculiar superfamily of metalloproteins.     

Multiple receptor conformation docking and dock pose clustering as tool for CoMFA and CoMSIA analysis – a case study on HIV-1 protease inhibitors

Multiple receptors conformation docking (MRCD) and clustering of dock poses allows seamless incorporation of receptor binding conformation of the molecules on wide range of ligands with varied structural scaffold. The accuracy of the approach was tested on a set of 120 cyclic urea molecules having HIV-1 protease inhibitory activity using 12 high resolution X-ray crystal structures and one NMR resolved conformation of HIV-1 protease extracted from protein data bank. A cross validation was performed on 25 non-cyclic urea HIV-1 protease inhibitor having varied structures. The comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) models were generated using 60 molecules in the training set by applying leave one out cross validation method, r_loo² values of 0.598 and 0.674 for CoMFA and CoMSIA respectively and non-cross validated regression coefficient r² values of 0.983 and 0.985 were obtained for CoMFA and CoMSIA respectively. The predictive ability of these models was determined using a test set of 60 cyclic urea molecules that gave predictive correlation (r_pred²) of 0.684 and 0.64 respectively for CoMFA and CoMSIA indicating good internal predictive ability. Based on this information 25 non-cyclic urea molecules were taken as a test set to check the external predictive ability of these models. This gave remarkable out come with r_pred² of 0.61 and 0.53 for CoMFA and CoMSIA respectively. The results invariably show that this method is useful for performing 3D QSAR analysis on molecules having different structural motifs.     

Are spontaneous activity and supraspinal control co-responsible for functional development of the generator of embryonic motility?

The effect of chronic administration of phenobarbital (from the 4th to the 16th day of incubation) combined with chronic spinal decentralization (decapitation at stage 11-13) on the development of spontaneous motor activity (recorded on the 17th day of incubation) was studied in 4 to 17-day-old chick embryos. 1. Combination of the two experimental treatments led to summation of their negative effect on development; spontaneous motor activity fell to 15.2% of the control value (to 26.9% after the isolated administration of phenobarbital and to 30.5% after isolated decapitation). 2. Metrazol activation of motor activity (100 mg/kg egg weight) after combination of the two factors was relatively no different from the results after their isolated use. 3. The acute administration of GABA (100 mg/kg e.w.) likewise induced relatively the same depression of spontaneous motility as after isolated chronic decapitation and the isolated chronic administration of phenobarbital. The results confirm the hypothesis of the significance of spontaneous activity of the spinal motoneurones for their survival and their actual functional development during the embryonic period.     

Arbuscular mycorrhiza increased the activity of a biotrophic leaf pathogen – is a compensation possible?

Arbuscular mycorrhizal barley-plants were more susceptible to the obligate biotrophic shoot pathogen Erysiphe graminis f. sp. hordei. In experiments under greenhouse and open-air conditions on leaves of mycorrhizal plants, the sporulation rate of the mildew fungus was more than twice that on control plants. However, mycorrhizal plants suffered less than non-mycorrhizal plants in terms of grain number, ear yield and thousand-grain weight. Disease-yield-relationship analysis showed that the symbiosis neutralised the positive correlation between disease severity and yield loss (up to 25% infected leaf area tested). After mildew infection, nitrogen in ears of non-mycorrhizal barley was higher because of an impaired starch accumulation during grain filling. In mycorrhizal plants, leaf disease did not impair either the quantity or quality of grain yield. This improved compensation in mycorrhizal plants was related to maintained photosynthetic capacity and a delay in pathogen-induced senescence. Thus filling of long-term storage pools (fructans in internodes) and consequently reallocation of these reserves during grain filling was improved. The results suggest that higher availability of energy and material during grain formation, together with longer physiological activity, were the basis of yield maintenance and, therefore, expression of mycorrhiza-induced tolerance towards the pathogen.     

Is fusion a trigger for myoblast differentiation?

Under normal culture conditions, fusion of myoblasts was strictly coordinated with the accumulation of various characteristic muscle enzymes as well as of myosin and actin. Nevertheless, it was not clear whether these two events depended on one another, in other words: is fusion a trigger for myoblast differentiation? We have approached this problem by blocking morphological differentiation by the use of cytochalasin B at the moment when the cells become ‘committed’. It is shown that fusion and accumulation of creatine phosphokinase and phosphorylase can be uncoupled. In view of our results, it seems that fusion is not absolutely necessary for the onset of increased synthesis of muscle-specific enzymes.     

Can the sheep model fully represent the human model for the functional evaluation of cervical interbody fusion cages?

Sheep model is the most favourable choice for animal study for functional evaluation of the cervical fusion prostheses before clinical application; however, significantly large differences between sheep and human existed in terms of morphological characteristics and daily-activity motions. Questions should be raised as whether the differences between the two species have influence on the reliability of sheep model. Finite element models (FEM) of the cervical spinal system were built to characterize the differences between the two species with respect to the range of motion (ROM) and biomechanical behaviour, and experimental cadaver tests on both species were employed for validation purposes. Results indicate that sheep model represents the worst-case scenario of the human model with exaggerated stresses (up to 3 times more) and ROM (up to 10 times more). Moreover, sheep model is very sensitive to the variation of prostheses design, whilst human model does not, which denotes that the sheep model provides a rather amplified effect of a certain design for its biomechanical performance. Therefore, caution needs to be taken when sheep models were used as the animal model for functional evaluation over various design, and the FEM built in this study can be employed as an effective methodology for performance evaluation of cage prostheses of cervical spine.

     

Is the alpha rhythm a control parameter for brain responses?

 The main goal of the present study is to develop a conceptual analysis of alpha response in the brain based on single sweep evaluation. A new method was employed to estimate a set of single-sweep parameters and quantify the oscillatory behaviour of single, electroencephalograph (EEG) sweeps. It was aimed to demonstrate that brain alpha responses are governed by spontaneous alpha activity and to validate the principle of brain response excitability. Because the spontaneous alpha activity depends on both the topology of recording and the subject’s age, topology and age models were used. Spontaneous and evoked alpha activity were recorded at frontal and occipital sites in three groups of subjects: 3-year-old children, young adults and middle-aged subjects. Amplitude, enhancement and phase-locking of single alpha responses to visual stimuli were analysed. Major results showed that: (1) visual alpha responses could be recorded only if the alpha rhythm was developed in the spontaneous EEG independent of electrode location; (2) middle-aged adults showed more expressed frontal spontaneous alpha activity in comparison with young adults; (3) accordingly, alpha responses with higher amplitude and stronger phase-locking were produced over the frontal brain area in middleaged than young adults. These results validate the principle of brain response excitability and demonstrate that a shift towards frontal brain areas for both the spontaneous and evoked alpha activity occurs with increasing age in adults. The results are discussed in the context of the diffuse and distributed alpha system of the brain. Age-dependent changes in frontal alpha activity are suggested to be related to frontal brain functioning during aging. Received: 6 November 1995 / Accepted in revised form: 13 March 1997     

Association of calpastatin with inactive calpain: a novel mechanism to control the activation of the protease?

It is generally accepted that the Ca(2+)-dependent interaction of calpain with calpastatin is the most relevant mechanism involved in the regulation of Ca(2+)-induced proteolysis. We now report that a calpain-calpastatin association can occur also in the absence of Ca(2+) or at very low Ca(2+) concentrations, reflecting the physiological conditions under which calpain retains its inactive conformational state. The calpastatin binding region is localized in the non-inhibitory L-domain containing the amino acid sequences encoded by exons 4-7. This calpastatin region recognizes a calpain sequence located near the end of the DII-domain. Interaction of calpain with calpastatins lacking these sequences becomes strictly Ca(2+)-dependent because, under these conditions, the transition to an active state of the protease is an obligatory requirement. The occurrence of the molecular association between Ca(2+)-free calpain and various recombinant calpastatin forms has been demonstrated by the following experimental results. Addition of calpastatin protected calpain from trypsin digestion. Calpain was coprecipitated when calpastatin was immunoprecipitated. The calpastatin molecular size increased following exposure to calpain. The two proteins comigrated in zymogram analysis. Furthermore, calpain-calpastatin interaction was perturbed by protein kinase C phosphorylation occurring at sites located at the exons involved in the association. At a functional level, calpain-calpastatin interaction at a physiological concentration of Ca(2+) represents a novel mechanism for the control of the amount of the active form of the protease potentially generated in response to an intracellular Ca(2+) influx.     

Sharing a predator: can an invasive alien pest affect the predation on a local pest?

Invasive species can strongly affect biotic interactions in ecosystems, interacting both directly and indirectly with local species. In European tomato greenhouses, the invasive alien pest Tuta absoluta may impact the population dynamics of other pests like whiteflies. Besides inducing damages to the host plant and competing for resources with local pests, this alien species may exert a predator-mediated interaction on local pests sharing common natural enemies. Biocontrol agents usually used against whiteflies may also prey upon T. absoluta and this could alter the dynamics of local pest populations. We evaluated possible resource competition and predator-mediated interactions in a system involving one mirid predator Macrolophus pygmaeus and two pests, T. absoluta and a local whitefly, Bemisia tabaci, on greenhouse tomatoes. Results showed that both resource competition and predator-mediated interactions occurred simultaneously. In the presence of the shared predator, there was a short-term positive effect of T. absoluta on B. tabaci [up to 5.9-fold increase of B. tabaci juveniles (egg + larvae) after four weeks]. However, in the long-term there was a negative predator-mediated interaction of T. absoluta on B. tabaci, i.e., after ten weeks the density of B. tabaci was 7.3-fold lower in the presence of the invasive pest. We emphasize the critical role of generalist predators in managing both local and invasive alien pest populations and that the strength and direction of predator-mediated indirect interactions can depend on the time scale considered.     

Microbial control in Asia: a bellwether for the future?

Advances and barriers faced by microbial control efforts in Asia offer instructive insights for microbial control in general. The papers in this series, which are based on plenary lectures given at the Society for Invertebrate Pathology 2006 meeting in Wuhan, China, explore the history and current status of microbial control in China, Japan, and Southeast Asia, and in doing so, bring to light the following key assumptions that deserve further examination; (1) the adoption rate of microbial control is well documented; (2) microbial control agents can compete directly with conventional insecticides; (3) microbial control agents are relatively easy and inexpensive to produce and develop; (4) patents will promote innovation and investor interest in microbial control. Alternative viewpoints are presented that can hopefully aid in future efforts to develop more safe and effective microbial control agents.