Interactions of two natural enemies of Tetranychus evansi, the fungal pathogen Neozygites floridana (Zygomycetes: Entomophthorales) and the predatory mite, Phytoseiulus longipes (Acari: Phytoseiidae)

Tetranychus evansi is an exotic pest of Solanaceous crops in Africa discovered in Zimbabwe in 1979. Two natural enemies, the predatory mite Phytoseiulus longipes and the fungal pathogen Neozygites floridana are important causes of mortality in T. evansi populations in Brazil. The first part of this study assessed the effects of N. floridana on predation and oviposition of P. longipes fed on N. floridana infected T. evansi and T. urticae. No N. floridana hyphal bodies were found in P. longipes after this feeding, demonstrating that N. floridana is not pathogenic to P. longipes and does not affect its oviposition. The second part of the study investigated the time spent on searching for and consuming of eggs on leaf discs with and without N. floridana capilliconidia. Both the searching and the feeding time on the first egg were similar on leaf discs with and without capilliconidia. When P. longipes was offered the choice of feeding on eggs on leaf discs with or without capilliconidia, the numbers of eggs consumed were not different. The only N. floridana effect observed on P. longipes was reduced egg predation. In addition, increased time spent grooming on leaf discs with capilliconidia was observed. P. longipes was efficient in removing most capilliconidia attached to the body through self-grooming behavior. This suggests that although the predator did not avoid areas with capilliconidia, it detected and removed most capilliconidia attached to the body. Increased grooming may account for the lower egg predation rates.     

Attenuation of the production of inositol 1,4,5-trisphosphate in the mouse vomeronasal organ by antibodies against the alphaq/11 subfamily of G-proteins

The social and reproductive behaviors of most mammals are modulated by pheromones, which are perceived by the vomeronasal organ (VNO). Vomeronasal transduction in vertebrates is activated through G-protein-coupled receptors, which in turn leads to the generation of inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG) by the activity of phospholipase C. DAG has been shown to gate the transient receptor potential channel 2, whereas IP(3) may play a role in stimulating the release of calcium from the endoplasmic reticulum store. To investigate the role of the alpha subunits of G(q/11) in the transduction process, microvillar membranes from female mice VNO were preincubated with a selective C-terminal peptide antibody against Galpha(q/11) and then stimulated with adult male urine. Incubation of VNO membranes with antibodies against Galpha(q/11) blocked the production of IP(3) in a dose-dependent manner. We were also able to impair the production of IP(3) when we stimulated with 2-heptanone or 2,5-dimethylpyrazine in the presence of antibodies against the alpha subunit of G(q/11). 2-Heptanone is a known pheromone that has been linked to VIR receptors. Thus, our observations indicate that the alpha subunits of G(q/11) play a role in pheromonal signaling in the VNO.     

Removal of the vomeronasal organ reduces reproductive performance and aggression in male prairie voles

Several short-duration tests have demonstrated that the surgicalremoval of the vomeronasal organ (VNX) from sexually-inexperiencedmale rodents results in a reduction in copulatory behavior,compared to the effects of sham surgery (SHAM). We extendedthese studies to adult male prairie voles, Microtus ochrogaster,and substantially increased the duration of the tests. Duringthe initial interactions with females, VNX males spent significantlyless time with their noses in close proximity to the femalesthan did SHAM males. Moreover, only two of nine VNX males siredoffspring after having been paired with females for 8 weeks,whereas nine of 12 SHAM males sired offspring in that interval.We also found that VNX and SHAM males were equivalently non-aggressiveto an anesthetized stimulus-male prior to being paired withfemales. However, after spending 2 weeks paired with a female,the VNX males were significantly less aggressive than were theSHAM males, possibly as a result of having copulated less often.In a later test, nearly all of the VNX and SHAM males that siredoffspring were vigorously aggressive to a stimulus male. Weconclude that the stimulation of the vomeronasal system in sexually-inexperiencedmale prairie voles is important for miximal reproductive performanceand that the VNX-induced impairment in reproduction is associatedwith a decrease in inter-male aggression. The possible sensoryeffects of the vomeronasal system on the neural and endocrinecontrol of reproduction and behavior are discussed.     

Design,synthesis and biological evaluation of new carbazole derivatives as anti-cancer and anti-migratory agents

Based on the efficacy of EHop-016 as an inhibitor of migration and Rac1 activation, a new series of carbazole derivatives has been synthesized. Cytotoxic and anti-migratory effects of these compounds were evaluated in MCF-7 and MDA-MB-231 breast cancer cell lines. Preliminary investigations of their anticancer activity demonstrated that several compounds have moderate antiproliferative effects on cancer cell lines with GI₅₀ values in the range of 13–50?µM. Furthermore, compounds 3b and 11b inhibit migration activity of metastatic cell line MDA-MB-231 by 32% and 34%, respectively. Compound 11b was shown to inhibit activation of the Rho GTPase Rac1 by 55% at 250?nM in both MDA-MB-231 and MDA-MB-435 cell lines. Compared with the IC₅₀ of Rac1 inhibition by lead compound EHop-016 of 1.1?µM, compound 11b demonstrates 4X improved in vitro efficacy.     

Genetic Diversity and Population Structure of Acacia senegal (L) Willd. in Kenya

The level of genetic diversity and population structure of Acacia senegal variety kerensis in Kenya was examined using seven polymorphic nuclear microsatellite loci and two chloroplast microsatellite loci. In both chloroplast and nuclear datasets, high levels of genetic diversity were found within all populations and genetic differentiation among populations was low, indicating extensive gene flow. Analysis of population structure provided support for the presence of two groups of populations, although all individuals had mixed ancestry. Groups reflected the influence of geography on gene flow, with one representing Rift Valley populations whilst the other represented populations from Eastern Kenya. The similarities between estimates derived from nuclear and chloroplast data suggest highly effective gene dispersal by both pollen and seed in this species, although population structure appears to have been influenced by distributional changes in the past. The few contrasts between the spatial patterns for nuclear and chloroplast data provided additional support for the idea that, having fragmented in the past, groups are now thoroughly mixed as a result of extensive gene flow. For the purposes of conservation and in situ management of genetic resources, sampling could target a few, large populations ideally distributed among the spatial groups identified. This should ensure the majority of extant variation is preserved, and facilitate the investigation of variation in important phenotypic traits and development of breeding populations.     

The dynamics of the MgATP-driven closure of MalK, the energy-transducing subunit of the maltose ABC transporter

The nucleotide binding domains (NBDs) are the energy supplying subunits of ATP-binding cassette (ABC) proteins. They power transport by binding and hydrolyzing ATP. Tracing the pathway between different conformational states of the NBDs during ATP binding, hydrolysis, and release has, however, proven difficult. We have used molecular dynamics simulations to study the ATP-driven association of the NBDs of the maltose ABC transporter, MalK, based on the crystal structures of its open and semiopen dimers. When MgATP was introduced into the binding pockets, the semiopen dimer transitioned to a closed conformation, whereas the open dimer evolved to a semiopen state. In the absence of docked MgATP, however, the twin NBDs of both the open and semiopen starting configurations drifted further apart. Both the presence of MgATP and direct cross-interface protein-protein hydrogen bonds, primarily involving the D-loop, quite likely play a key role in initiating closure. The simulations of the MgATP-docked semiopen form indicate that completion of closure is driven mainly by cross-interface contacts between the gamma-phosphate of ATP and residues in the signature motif. Our simulations also give insight into possible interactions of MalK with the regulatory proteins MalT and enzyme IIA(glc).     

Dp71f Modulates GSK3-β Recruitment to the β1-Integrin Adhesion Complex

Previously, it was shown that Dp71f binds to the β1-integrin adhesion complex to modulate PC12 cell adhesion. The absence of Dp71f led to a failure in the β1-integrin adhesion complex formation. One of the structural proteins which links the β1-integrin cytoplasmic domain to the actin cytoskeleton is ILK. GSK3-β is an ILK substrate and the carboxi-terminal region of dystrophin 427 is a substrate for hierarchical phosphorylation by GSK3-β. Dp71f contains the carboxi-terminal domain present in dystrophin 427. By using co-immunoprecipitation assays, in the present work it is demonstrated that in the neuronal PC12 cell line an interaction between Dp71f and GSK3-β occurs. This interaction was corroborated by in vitro pulldown assays. We show that GSK3-β is recruited to the β1-integrin complex and that a reduced expression of Dp71f induces a reduced GSK3-β recruitment to the β1-integrin complex. In addition, the present work establishes that adhesion of PC12 cells to laminin does not influence the phosphorylation status of Dp71f.     

Impact of natural epizootics of the fungal pathogen Neozygites floridana (Zygomycetes: Entomophthorales) on population dynamics of Tetranychus evansi (Acari: Tetranychidae) in tomato and nightshade

The tomato red spider mite, Tetranychus evansi (Acari: Tetranychidae) was recently introduced in Africa and Europe, where there is an increasing interest in using natural enemies to control this pest on solanaceous crops. Two promising candidates for the control of T. evansi were identified in South America, the fungal pathogen, Neozygites floridana and the predatory mite Phytoseiulus longipes. In this study, population dynamics of T. evansi and its natural enemies together with the influence of environmental conditions on these organisms were evaluated during four crop cycles in the field and in a protected environment on nightshade and tomato plants with and without application of chemical pesticides. N. floridana was the only natural enemy found associated with T. evansi in the four crop cycles under protected environment but only in the last crop cycle in the field. In the treatments where the fungus appeared, reduction of mite populations was drastic. N. floridana appeared in tomato plants even when the population density of T. evansi was relatively low (less than 10 mites/3.14 cm² of leaf area) and even at this low population density, the fungus maintained infection rates greater than 50%. The application of pesticides directly affected the fungus by delaying epizootic initiation and contributing to lower infection rates than unsprayed treatments. Rainfalls did not have an apparent impact on mite populations. These results indicate that the pathogenic fungus, N. floridana can play a significant role in the population dynamics of T. evansi, especially under protected environment, and has the potential to control this pest in classical biological control programs.     

Computer simulations of membrane proteins

Computer simulations are rapidly becoming a standard tool to study the structure and dynamics of lipids and membrane proteins. Increasing computer capacity allows unbiased simulations of lipid and membrane-active peptides. With the increasing number of high-resolution structures of membrane proteins, which also enables homology modelling of more structures, a wide range of membrane proteins can now be simulated over time spans that capture essential biological processes. Longer time scales are accessible by special computational methods. We review recent progress in simulations of membrane proteins.     

Computer simulations of ABC transporter components.

Current computer simulation techniques provide robust tools for studying the detailed structure and functional dynamics of proteins, as well as their interaction with each other and with other biomolecules. In this minireview, we provide an illustration of recent progress and future challenges in computer modeling by discussing computational studies of ATP-binding cassette (ABC) transporters. ABC transporters have multiple components that work in a well coordinated fashion to enable active transport across membranes. The mechanism by which members of this superfamily execute transport remains largely unknown. Molecular dynamics simulations initiated from high-resolution crystal structures of several ABC transporters have proven to be useful in the investigation of the nature of conformational coupling events that may drive transport. In addition, fruitful efforts have been made to predict unknown structures of medically relevant ABC transporters, such as P-glycoprotein, using homology-based computational methods. The various techniques described here are also applicable to gaining an atomically detailed understanding of the functional mechanisms of proteins in general.