Ultrastructural localization and identification ofAzospirillum brasilense Cd on and within wheat root by immuno-gold labeling

Azospirillum brasilense Cd localization in wheat roots was studied by light microscopy, by scanning, and by transmission electron microscopy.A. brasilense Cd cells were specifically identified immunocytochemically around and within root tissues.A. brasilense Cd cells found both outside and inside inoculated roots were intensively labeled with colloidal gold. In non-axenic cultures other bacterial strains or plant tissue were not labeled, thereby providing a non-interfering background. The roots of axenic grown wheat plants were colonized both externally and internally byA. brasilense Cd after inoculation, whereas non-axenic cultures were colonized by other bacterial strains as well.A. brasilense Cd cells were located on the root surface along the following zones: the root tip, the elongation, and the root-hair zone. However, bacteria were located within the cortex only in the latter two zones. In a number of observations, an electron dense material mediated the binding of bacterial cells to outer surfaces of epidermal cells, or between adjacent bacterial cells.A. brasilense Cd were found in root cortical intercellular spaces, but were not detected in either the endodermal layer or in the vascular system. This study proposes that in addition to root surface colonization,A. brasilense Cd forms intercellular associations within wheat roots.     

Alginate Beads as Synthetic Inoculant Carriers for Slow Release of Bacteria That Affect Plant Growth

Uniform synthetic beads were developed as carriers for the bacterial inoculation of plants. The beads are made of sodium alginate and skim milk and contain a large reservoir of bacterial culture which releases the bacteria at a slow and constant rate. The beads are biodegradable and produce no environmental pollution. The strength of the beads, the rate of bacterial release, and the time of their survival in the soil can be controlled by several hardening treatments. The final product, lyophilized beads, is simple to use and is applied to the seeds concomitantly with sowing. The released bacteria are available for root colonization immediately at seed germination. Dry beads containing bacteria can be stored at ambient temperature over a long period without loss of bacterial content; storage requires a limited space, and the quality control of a number of bacteria in the bead is simple. The level of plant inoculation with beads was similar to that with previously used peat inoculants, but the former method yielded more consistent results, as the frequency of inoculated plants was much higher. The former method provides a different approach for inoculation of plants with beneficial rhizosphere bacteria.     

Inhibition of Seed Germination and Root Development Caused by Xanthomonas campestris pv. vesicatoria in Pepper and Tomato

Inoculation of pepper seeds with the leaf pathogen Xanthomonas campestris pv. vesicatoria inhibited pepper germination. The inhibitory effect, which was stronger in non-sterilized light textured soils, decreased with time, and after 20, days or more, there was no difference between inoculated and non-inoculated seeds. Inhibitory substance(s) within the cytoplasmatic fraction of pathogen cells inhibited the germination of non-host tomato seeds. No relationship between pathogenicity to pepper leaves and inhibition of pepper seed germination was detected. The inhibitory substance(s) was found in two out of four X. campestris pv. vesicatoria strains. Heat-killed bacteria suppressed growth of pepper but not tomato seedlings. It is, therefore, suggested that the inhibition of seed germination and the decrease in root development are different modes of X. campestris pv. vesicatoria pathogenesis toward pepper plants.     

Characteristics of cystine counter-transport in normal and cystinotic lysosome-rich leucocyte granular fractions.

Normal leucocyte lysosome-rich granular fractions exhibited counter-transport of cystine, confirming that cystine transport across the lysosomal membrane is carrier-mediated. The trans-activation of cystine transport was temperature-dependent but relatively independent of the external Na+ or K+ concentration in phosphate buffer. Counter-transport, measured as uptake of exogenous [3H]cystine, increased with increasing intralysosomal cystine content up to approx. 3 nmol of half-cystine/unit of hexosaminidase activity. The amount of [3H]cystine entering lysosomes loaded with unlabelled cystine decreased when unlabelled cystine was added to the extralysosomal medium. Lysosomal cystine counter-transport was stereospecific for the L-isomer. Cystathionine, cystamine and cysteamine-cysteine mixed disulphide gave evidence of sharing the lysosomal cystine-transport system, although at lower activity than cystine. Other tested amino acids, including arginine, glutamate and homocystine, were inactive in this system. Nine leucocyte lysosome-rich preparations from eight different cystinotic patients displayed virtually no counter-transport of cystine, conclusively establishing that a carrier-mediated system for cystine transport is dysfunctional in cystinotic lysosomes.     

Active attachment ofAzospirillum brasilense to root surface of non-cereal plants and to sand particles

The rhizosphere bacteriumAzospirillum brasilense Cd adsorbed strongly to light-textured and heavy-textured soils, but only slightly to quartz sand. Bacterial attachment to sand particles was mediated by a network made up of various sizes and shapes of fibrillar material. Inoculation of sand with an aggregate-deficient mutant resulted in no detectable fibrillar formation. Rinsing or agitating the sand, colonized by the wild-type and the mutant, had a greater effect on the mutant than on the parental strain. We propose that bacterial fibrils are essential for anchoring ofA. brasilense to sand. A. brasilense Cd was capable of efficiently colonizing the elongation and root-hair zones of tomato, pepper, cotton and soybean plants as well as of wheat plants. All inoculated plants demonstrated: (i) larger amounts of a mucigel-like substance on the root surface than non-inoculated plants, and (ii) fibrillar material which anchored the bacterial cells to the root surface. These fibrils established also connections between cells within bacterial aggregates. On non-water stressed soybean roots, mostA. brasilense Cd cells occurred as vibroid forms. Whereas, those on roots of water-stressed plants.(wilting) were cyst-like. A lower rhizosphere bacterial population was observed on water-stressed plants. When water stress conditions were eliminated, cells reverted to the vibroid form. A concomitant increase in the bacterial population was observed. We suggest that cyst-like formation is a natural response forA. brasilense Cd in the rhizosphere of water-stressed plants.     

Alterations in membrane potential and in proton efflux in plant roots induced byAzospirillum brasilense

Inoculation of soybean seedlings withAzospirillum brasilense Cd significantly reduced the membrane potential in every root part and was being maximal in the root elongation zone. Monitoring the proton efflux pattern of inoculated wheat roots by severalA. brasilense strains and byPseudomonas sp. for prolonged periods (up to 200h) revealed a change from the bimodal pattern of proton efflux of non inoculated roots. This change was not related to root colonization ability but to bacterial capacity to induce changes in root surface area. Continuous perfusion of the plant nutrient solution with a fresh solution (from inoculation time), eliminated the enhancing effect of inoculation on proton efflux. We propose thatA. brasilense inoculation influences membrane activity and subsequently proton efflux in roots, probably through the release of an as yet unidentified bacterial signal.     

Associating quantitative behavioral traits with gene expression in the brain: searching for diamonds in the hay

Gene expression and phenotypic functionality can best be associated when they are measured quantitatively within the same experiment. The analysis of such a complex experiment is presented, searching for associations between measures of exploratory behavior in mice and gene expression in brain regions. The analysis of such experiments raises several methodological problems. First and foremost, the size of the pool of potential discoveries being screened is enormous yet only few biologically relevant findings are expected, making the problem of multiple testing especially severe. We present solutions based on screening by testing related hypotheses, then testing the hypotheses of interest. In one variant the subset is selected directly, in the other one a tree of hypotheses is tested hierarchical; both variants control the False Discovery Rate (FDR). Other problems in such experiments are in the fact that the level of data aggregation may be different for the quantitative traits (one per animal) and gene expression measurements (pooled across animals); in that the association may not be linear; and in the resolution of interest only few replications exist. We offer solutions to these problems as well. The hierarchical FDR testing strategies presented here can serve beyond the structure of our motivating example study to any complex microarray study. Supplementary information: Supplementary data are available at Bioinformatics online.     

Anxiolytic effects of a novel herbal treatment in mice models of anxiety

AimsAnxiety and stress disorders are currently among the ten most important public health concerns, and in recent years, have reached epidemic proportions. The current success rate of treatments for anxiety disorders is not high, reaching 50% at most. These treatments are also associated with a wide variety of side effects. The aim of the present study was to investigate the anxiolytic properties of a novel herbal treatment produced in our laboratory compared to a conventional treatment for anxiety disorders, namely SSRIs.Main methodsAnxiety-like behavior was evaluated in adult mice exposed to stress during childhood following 1, 2 and 3 weeks of treatment with the novel herbal treatment or escitalopram, using the novel open field and the elevated plus maze paradigms. The behavioral evaluation in these mice was followed by a biochemical assessment of their brain hippocampal BDNF levels and blood corticosterone levels.Key findingsThe study showed that (1) the novel herbal treatment reduced anxiety-like behaviors in both behavioral tests. Interestingly, this reduction was observed only following a 3-week treatment; (2) following the novel treatment, corticosterone levels in the plasma of treated mice were reduced and this reduction was similar to the one observed following escitalopram treatment; and (3) BDNF levels in the hippocampus of mice treated both with the novel herbal treatment and escitalopram were increased.SignificanceThese behavioral and biological findings indicate that our novel herbal compound has the potential of being highly efficacious in treating anxiety disorders.     

Responses of Second-Instar Male Nymphs of Four Mealybug Species (Hemiptera: Pseudococcidae) to Conspecific and Heterospecific Female Sex Pheromones

The response of the late second-instar male nymphs of the mealybug species (Hemiptera, Pseudococcidae), Planococcus citri (Risso), Planococcus ficus (Signoret), Pseudococcus cryptus Hempel Nipaecoccus viridis (Newstead), to their conspecific and heterospecific female pheromone was studied. Males that exhibited the typical appearance of late-second-instar nymphs were tested. The male behavior was monitored soon after their exposure to the tested female sex pheromone in glass Petri dish arenas. Male nymph behavior toward the pheromone source was characterized based on their aggregation on the disks in the arena. Males of all four tested mealybug species were attracted to their conspecific female pheromone. By contrast, almost no interceptions of male nymphs with disks impregnated with a heterospecific female pheromone were observed. The mode of attraction of each of male nymphs of P. ficus, among most of the tested individuals (>80%), to the conspecific female sex pheromone, (S)-lavandulyl senecioate and or (S)-lavandulyl isovalerate, was the same as the mode of attraction latter on as adult. We suggest that by being attracted to the conspecific pheromone these males may direct themselves to a suitable pupation site near conspecific non-sibling mature females, thus preventing inbreeding. The repellency of heterospecific sex pheromone to males that are looking for a pupation site suggests that the latter try to avoid close contact with heterospecific females.