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411.
Synthetic Herbivore-induced Plant Volatiles Increase Field Captures of Parasitic Wasps 总被引:1,自引:0,他引:1
Field evidence for attraction of parasitic wasps from the families Encyrtidae and Mymaridae to grapevines baited with synthetic
versions of three herbivore-induced plant volatiles (HIPV) is presented. In a replicated experiment conducted in a juice grape
vineyard, sticky cards in blocks baited with controlled-release dispensers of methyl salicylate (MeSA), methyl jasmonate (MeJA)
or (Z)-3-hexenyl acetate (HA), trapped significantly greater numbers of Metaphycus sp. (Encyrtidae) than cards in unbaited blocks during May–September. Significantly greater numbers of Anagrus spp. (Mymaridae) were trapped in MeSA and MeJA-baited blocks than in unbaited blocks, during August–September. Greater numbers
were recorded in HA-baited blocks in September only. Previous studies showed Encyrtidae and Anagrus spp. were not attracted to sticky cards baited with vials of MeSA, MeJA or HA. Possible reasons for attraction in this study
are discussed including the possibility that synthetic, gaseous HIPV from controlled-release dispensers may stimulate plants
to produce natural blends of parasitoid-attracting volatiles. 相似文献
412.
413.
Gordon T Thomas CK Munson JB Stein RB 《Canadian journal of physiology and pharmacology》2004,82(8-9):645-661
Henneman's size principle relates the input and output properties of motoneurons and their muscle fibers to size and is the basis for size-ordered activation or recruitment of motor units during movement. After nerve injury and surgical repair, the relationship between motoneuron size and the number and size of the muscle fibers that the motoneuron reinnervates is initially lost but returns with time, irrespective of whether the muscles are self- or cross-reinnervated by the regenerated axons. Although the return of the size relationships was initially attributed to the recovery of the cross-sectional area of the reinnervated muscle fibers and their force per fiber, direct enumeration of the innervation ratio and the number of muscle fibers per motoneuron demonstrated that a size-dependent branching of axons accounts for the size relationships in normal muscle, as suggested by Henneman and his colleagues. This same size-dependent branching accounts for the rematching of motoneuron size and muscle unit size in reinnervated muscles. Experiments were carried out to determine whether the daily amount of neuromuscular activation of motor units accounts for the size-dependent organization and reorganization of motor unit properties. The normal size-dependent matching of motoneurons and their muscle units with respect to the numbers of muscle fibers per motoneuron was unaltered by synchronous activation of all of the motor units with the same daily activity. Hence, the restored size relationships and rematching of motoneuron and muscle unit properties after nerve injuries and muscle reinnervation sustain the normal gradation of muscle force during movement by size-ordered recruitment of motor units and the process of rate coding of action potentials. Dynamic modulation of size of muscle fibers and their contractile speed and endurance by neuromuscular activity allows for neuromuscular adaptation in the context of the sustained organization of the neuromuscular system according to the size principle. 相似文献
414.
Nall TA Chappell KJ Stoermer MJ Fang NX Tyndall JD Young PR Fairlie DP 《The Journal of biological chemistry》2004,279(47):48535-48542
West Nile Virus (WNV) is a mosquito-borne flavivirus with a rapidly expanding global distribution. Infection causes severe neurological disease and fatalities in both human and animal hosts. The West Nile viral protease (NS2B-NS3) is essential for post-translational processing in host-infected cells of a viral polypeptide precursor into structural and functional viral proteins, and its inhibition could represent a potential treatment for viral infections. This article describes the design, expression, and enzymatic characterization of a catalytically active recombinant WNV protease, consisting of a 40-residue component of cofactor NS2B tethered via a noncleavable nonapeptide (G4SG4) to the N-terminal 184 residues of NS3. A chromogenic assay using synthetic para-nitroanilide (pNA) hexapeptide substrates was used to identify optimal enzyme-processing conditions (pH 9.5, I <0.1 m, 30% glycerol, 1 mm CHAPS), preferred substrate cleavage sites, and the first competitive inhibitor (Ac-FASGKR-H, IC50 approximately 1 microm). A putative three-dimensional structure of WNV protease, created through homology modeling based on the crystal structures of Dengue-2 and Hepatitis C NS3 viral proteases, provides some valuable insights for structure-based design of potent and selective inhibitors of WNV protease. 相似文献
415.
Liu Y Burch-Smith T Schiff M Feng S Dinesh-Kumar SP 《The Journal of biological chemistry》2004,279(3):2101-2108
SGT1 and Rar1 are important signaling components of resistance (R) gene-mediated plant innate immune responses. Here we report that SGT1 and Rar1 associate with the molecular chaperone Hsp90. In addition, we show that Hsp90 associates with the resistance protein N that confers resistance to tobacco mosaic virus. This suggests that Hsp90-SGT1-Rar1 and R proteins might exist in one complex. Suppression of Hsp90 in Nicotiana benthamiana plants shows that it plays an important role in plant growth and development. In addition, Hsp90 suppression in NN plants compromises N-mediated resistance to tobacco mosaic virus. Our results reveal a new role for SGT1- and Rar1-associated chaperone machinery in R gene-mediated defense signaling. 相似文献
416.
Payne RB Casalot L Rivere T Terry JH Larsen L Giles BJ Wall JD 《Archives of microbiology》2004,181(6):398-406
Cytochrome c(3) of Desulfovibrio desulfuricans strain G20 is an electron carrier for uranium (VI) reduction. When D. desulfuricans G20 was grown in medium containing a non-lethal concentration of uranyl acetate (1 mM), the rate at which the cells reduced U(VI) was decreased compared to cells grown in the absence of uranium. Western analysis did not detect cytochrome c(3) in periplasmic extracts from cells grown in the presence of uranium. The expression of this predominant tetraheme cytochrome was not detectably altered by uranium during growth of the cells as monitored through a translational fusion of the gene encoding cytochrome c(3) ( cycA) to lacZ. Instead, cytochrome c(3) protein was found tightly associated with insoluble U(IV), uraninite, after the periplasmic contents of cells were harvested by a pH shift. The association of cytochrome c(3) with U(IV) was interpreted to be non-specific, since pure cytochrome c(3) adsorbed to other insoluble metal oxides, including cupric oxide (CuO), ferric oxide (Fe(2)O(3)), and commercially available U(IV) oxide. 相似文献
417.
418.
There are many potential sources of reactive oxidants around the time of birth and pre-term infants are considered to be particularly vulnerable to oxidative injury. To gain insight into these processes, we have measured biomarkers of lipid and protein oxidation in umbilical cord plasma and related concentrations to mode of delivery and gestational age. Protein carbonyls were measured by ELISA and malondialdehyde (MDA) by HPLC after reaction with thiobarbituric acid, for 54 pre-term (< or = 36 weeks gestational age) and 43 term infants. Protein carbonyls were significantly lower in pre-term (median for < 32 weeks gestational age 0.048nmol/mg protein) than in term infants (0.105 nmol/mg, p = 0.004), and were unrelated to mode of delivery. In contrast, MDA concentrations were higher in the very pre-term (<32 weeks gestation) group (2.47 compared with 1.83 microM for term infants, p < 0.0001). MDA concentrations were higher in infants who were born with labour compared with elective caesarean section. Pre-eclampsia in the mother was associated with higher cord blood MDA concentrations. The MDA results are consistent with other studies of this marker and could be interpreted as indicating increased oxidative stress associated with prematurity and labour. However, the lower protein carbonyls in pre-term infants would lead to an opposite interpretation. More information is needed on the source and fate of these and other biomarkers before drawing strong conclusions on how they reflect oxidative stress in this and other clinical situations. 相似文献
419.
Hanson BJ Carrozzo R Piemonte F Tessa A Robinson BH Capaldi RA 《The Journal of biological chemistry》2001,276(19):16296-16301
Cytochrome c oxidase (COX) deficiency is the most common respiratory chain defect in childhood and is clinically heterogeneous. We report a study of six patients with COX deficiencies. Two of the patients had as yet undefined defects, three patients had Surf-1 mutations, and one patient had a 15-base pair deletion in the COX III subunit. We show that quantitative measurements of steady-state levels of subunits by monoclonal antibody reactivity, when used in combination with a discontinuous sucrose gradient methods, provide an improved diagnosis of COX deficiencies by distinguishing between kinetic, stability, and assembly defects. The two mutants of undefined etiology had a full complement of subunits with one stable and the other partially unstable to detergent solubilization. Both are likely to carry mutations in nuclear-encoded subunits of the complex. The three Surf-1 mutants and the COX III mutant each had reduced steady-state levels of subunits but variable associations of the residual subunits. This information, as well as aiding in diagnosis, helps in understanding the genotype-phenotype relationships of COX deficiencies and provides insight into the mechanism of assembly of the enzyme complex. 相似文献
420.
Jürgen Homeier Dietrich Hertel Tessa Camenzind Nixon L. Cumbicus Mark Maraun Guntars O. Martinson L. Nohemy Poma Matthias C. Rillig Dorothee Sandmann Stefan Scheu Edzo Veldkamp Wolfgang Wilcke Hans Wullaert Christoph Leuschner 《PloS one》2012,7(10)
Tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems. Here, we show that Neotropical montane rainforests respond rapidly to moderate additions of N (50 kg ha−1 yr−1) and P (10 kg ha−1 yr−1). Monitoring of nutrient fluxes demonstrated that the majority of added nutrients remained in the system, in either soil or vegetation. N and P additions led to not only an increase in foliar N and P concentrations, but also altered soil microbial biomass, standing fine root biomass, stem growth, and litterfall. The different effects suggest that trees are primarily limited by P, whereas some processes—notably aboveground productivity—are limited by both N and P. Highly variable and partly contrasting responses of different tree species suggest marked changes in species composition and diversity of these forests by nutrient inputs in the long term. The unexpectedly fast response of the ecosystem to moderate nutrient additions suggests high vulnerability of tropical montane forests to the expected increase in nutrient inputs. 相似文献