Antifungal compounds from plants

Due to the increase of the incidence of fungal infections in humans and the limitations of the available antimycotic drugs, among which the emergence of resistant strains, there is a need for the discovery of new antifungal agents. Plants, especially those used in Traditional Medicine, linked to an unmatched chemical diversity, either as pure compounds or as plant extracts, provide unlimited opportunities for the development of new antifungals. Inrecent years, compounds from different phytochemical groups have been described as having antifungal activity, including polyphenols, saponins, or peptides, among others, as well asessential oils and their constituents. After screening of ethnopharmacologically selected plants, mainly from Latin-America, followed by bio-guided isolation, our group hasdescribed the antifungal activity of different types of plant constituents, such as sesquiterpenes, triterpenes, flavonoids, lignans, fatty acids and essential oils.

Effects of leaf compounds, climate and natural enemies on the incidence of thrips in cassava

The objective of this study was to determine the effects of rainfall, temperature, sunlight and relative humidity, as well as predators and parasitoids, leaf chemical composition and levels of leaf nitrogen and potassium on the intensity of Scirtothrips manihoti (Thysanoptera: Thripidae) attack on cassava Manihot esculenta Crantz var. Cacau. The leaf compounds (E)-farnesene/trans-farnesol and D-friedoolean-14-en-3-one correlated significantly with the population of S. manihoti. Insect population decreased in the dry and cold season probably due to leaf senescence. Significative correlation was observed between Syrphidae with S. manihoti populations.

Synthesis of a non-peptidic PET tracer designed for α5β1 integrin receptor.

Arginine-glycine-aspartic acid (RGD)-containing peptides have been traditionally used as PET probes to noninvasively image angiogenesis, but recently, small selective molecules for α5 β1 integrin receptor have been developed with promising results. Sixty-one antagonists were screened, and tert-butyl (S)-3-(2-((3R,5S)-1-(3-(1-(2-fluoroethyl)-1H-1,2,3-triazol-4-yl)propanoyl)-5-((pyridin-2-ylamino)methyl)pyrrolidin-3-yloxy)acetamido)-2-(2,4,6-trimethylbenzamido)propanoate (FPMt) was selected for the development of a PET tracer to image the expression of α5 β1 integrin receptors. An alkynyl precursor (PMt) was initially synthesized in six steps, and its radiolabeling was performed according to the azide-alkyne copper(II)-catalyzed Huisgen's cycloaddition by using 1-azido-2-[(18)F]fluoroethane ([(18)F]12). Different reaction conditions between PMt and [(18)F]12 were investigated, but all of them afforded [(18)F]FPMt in 15 min with similar radiochemical yields (80-83%, decay corrected). Overall, the final radiopharmaceutical ([(18)F]FPMt) was obtained after a synthesis time of 60-70 min in 42-44% decay-corrected radiochemical yield.

Geochemical evolution of active porphyry copper tailings impoundments : from alkaline deposition towards acidification

J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Thesis abstract Mine waste is the largest volume of materials handled in the world. The oxidation of sulfidic mine waste may result in the release of acid mine drainage (AMD) rich in heavy metals and arsenic to the environment, one of the major problems the mining industry is facing today. To control and reduce this environmental impact, it is crucial to identify the main geochemical and hydrological processes influencing contaminant liberation, transport, and retention. This thesis presents the results of a geochemical, mineralogical and stable isotope study (δ2H, δ18O, δ34S) from two active porphyry copper tailings impoundments in Mediterranean (Carén tailings impoundment, El Teniente mine, Central Chile) and hyper-arid climate (Talabre tailings impoundment, Chuquicamata, Northern Chile) from the deposition in alkaline environment (pH 10.5) towards acidification after several years of exposure. The major hydrological results were the identification of vertical contaminant and water transport in the uppermost, not water-saturated zone, triggered by capillary rise due to evaporation, and infiltration downwards due to new tailings deposition, and of horizontal transport in the groundwater zone. At the surface of the sedimented tailings, evaporation of pore water led to the precipitation of Na-Ca-Mg sulfates (e.g., gypsum, tenorite), in hyper-arid climate also halite. At the Carén tailings impoundment, renewed deposition in a 4-week interval inhibited a pH decrease below neutral values and the formation of an efflorescent salt crust. At the Talabre tailings impoundment, deposition breaks of several years resulted in the formation of acidic oxidation zones in the timeframe of less than 4 years. This process enabled the transport of liberated Cu, Zn, and Fe via capillary rise to the surface, where these metals precipitated as heavy-metal sulfates (e.g., devilline, krohnkite) and chlorides (eriochalcite, atacamite). Renewed depositing may dissolve efflorescent salts and transport liberated elements towards the groundwater zone. This zone was found to be highly dynamic due to infiltration and mixing with water from different sources, like groundwater, catchment water, and infiltration from superficial waters. There, Cu was found to be partially mobile due to complexation with Cl (in Cl-rich groundwater, Talabre) and dissolved organic matter (in zones with infiltration of catchment water rich in dissolved organic matter, Carén). A laboratory study on the isotopic fractionation of sulfur and oxygen of sulfate in different minerals groups (water-soluble sulfates, low- and high-crystalline Fe(III) oxyhydroxides) contributed to the use of stable isotopes as tracer of geochemical and transport processes for environmental studies. The results highlight that a detailed geochemical, stable isotope and mineralogical study permits the identification of contamination processes and pathways already during the deposition of mine tailings. This knowledge allows the early planning of adequate actions to reduce and control the environmental impact during tailings deposition and after the closing of the impoundment. J. Smuda: Geochemical evolution of active porphyry copper tailings impoundments Résumé de these Les déchets miniers constituent les plus grands volumes de matériel gérés dans le monde. L'oxydation des déchets miniers sulfuriques peut conduire à la libération de drainages miniers acides (DMA) riches en métaux et arsenic dans l'environnement, ce qui est l'un des principaux problèmes de l'industrie minière aujourd'hui. Pour contrôler et réduire ces impacts sur l'environnement, il est crucial d'identifier les principaux processus géochimiques et hydrologiques influençant la libération, le transport et la rétention des contaminants. Cette thèse présente les résultats d'une étude géochimique, minéralogique et des isotopes stables (δ2H, δ18O, δ34S) sur des déchets miniers de 2 sites de dépôt actifs en climat méditerranéen (Dépôt de déchets de Carén, mine de El Teniente, Centre du Chili) et en climat hyper-aride (Dépôt de déchets de Talabre, mine de Chuquicamata, Nord du Chili). L'objectif était d'étudier l'évolution des déchets de la déposition en milieu alcalin (pH = 10.5) vers l'acidification après plusieurs années d'exposition. Le principal résultat hydrologique a été l'identification de 2 types de transport : un transport vertical de l'eau et des contaminants dans la zone non saturée en surface, induit par la montée capillaire due à l'évaporation et par l'infiltration subséquente de la déposition de sédiments frais ; et un transport horizontal dans la zone des eaux souterraines. À la surface des déchets, l'évaporation de l'eau interstitielle conduit à la précipitation de sulfates de Na-Ca-Mg (ex. gypse, ténorite) et halite en climat hyper-aride. Dans le site de Carén, une nouvelle déposition de déchets frais à 4 semaines intervalle a empêché la baise du pH en deçà des valeurs neutres et la formation d'une croûte de sels efflorescentes en surface. Dans le site de Talabre, les fentes de dessiccation des dépôts ont entraîné la formation d'une zone d'oxydation à pH acide en moins de 4 ans. Ce processus a permis la libération et le transport par capillarité de Cu, Zn, Fe vers la surface, où ces éléments précipitent sous forme de sulfates de métaux lourds (ex., dévilline, krohnkite) de chlorures (ex. ériochalcite, atacamite). Une nouvelle déposition de sédiments frais pourrait dissoudre ces sels et les transporter vers la zone des eaux souterraines. Cette dernière zone était très dynamique en raison du mélange d'eaux provenant de différentes sources, comme les eaux souterraines, l'eau de captage et l'infiltration des eaux superficielles. Egalement dans cette zone, le cuivre était partiellement mobile à cause de la formation de complexe avec le chlore (dans les zone riche en Cl, Talabre) et avec la matière organique dissoute (dans les zones où s'infiltre l'eau de captage riche en matière organique, Carén). Une étude en laboratoire sur le fractionnement des isotopes stables de sulfure et d'oxygène des sulfates dans différents groupes de minéraux (sulfates hydrosolubles, sulfures de oxy-hydroxyde de Fe(III) faiblement ou fortement cristallins) a permis d'apporter une contribution à leur utilisation comme traceurs dans l'étude des processus géochimiques et de transport lors d'études environnementales. Les résultats montrent qu'une étude détaillée de la géochimie, des isotopes stables et de la minéralogie permet d'identifier les processus et les voies de contamination déjà pendant la période de dépôt des déchets miniers. Cette connaissance permet de planifier, dès le début de l'exploitation, des mesures adéquates pour réduire et contrôler l'impact sur l'environnement pendant la période de dépôts de déchets miniers et après la fermeture du site.

Comparison of the developmental effects of two mercury compounds on glial cells and neurons in aggregate cultures of rat telencephalon.

A three-dimensional cell culture system was used as a model to study the influence of low levels of mercury in the developing brain. Aggregating cell cultures of fetal rat telencephalon were treated for 10 days either during an early developmental period (i.e., between days 5 and 15 in vitro) or during a phase of advanced maturation (i.e., between days 25 and 35) with mercury. An inorganic (HgCl2) and an organic mercury compound (monomethylmercury chloride, MeHgCl) were examined. By monitoring changes in cell type-specific enzymes activities, the concentration-dependent toxicity of the compounds was determined. In immature cultures, a general cytotoxicity was observed at 10(-6) M for both mercury compounds. In these cultures, HgCl2 appeared somewhat more toxic than MeHgCl. However, no appreciable demethylation of MeHgCl could be detected, indicating similar toxic potencies for both mercury compounds. In highly differentiated cultures, by contrast, MeHgCl exhibited a higher toxic potency than HgCl2. In addition, at 10(-6) M, MeHgCl showed pronounced neuron-specific toxicity. Below the cytotoxic concentrations, distinct glia-specific reactions could be observed with both mercury compounds. An increase in the immunoreactivity for glial fibrillary acidic protein, typical for gliosis, could be observed at concentrations between 10(-9) M and 10(-7) M in immature cultures, and between 10(-8) M and 3 x 10(-5) M in highly differentiated cultures. A conspicuous increase in the number and clustering of GSI-B4 lectin-binding cells, indicating a microglial response, was found at concentrations between 10(-10) M and 10(-7) M. These development-dependent and cell type-specific effects may reflect the pathogenic potential of long-term exposure to subclinical doses of mercury.

Adaptation of aerobically growing Pseudomonas aeruginosa to copper starvation.

Restricted bioavailability of copper in certain environments can interfere with cellular respiration because copper is an essential cofactor of most terminal oxidases. The global response of the metabolically versatile bacterium and opportunistic pathogen Pseudomonas aeruginosa to copper limitation was assessed under aerobic conditions. Expression of cioAB (encoding an alternative, copper-independent, cyanide-resistant ubiquinol oxidase) was upregulated, whereas numerous iron uptake functions (including the siderophores pyoverdine and pyochelin) were expressed at reduced levels, presumably reflecting a lower demand for iron by respiratory enzymes. Wild-type P. aeruginosa was able to grow aerobically in a defined glucose medium depleted of copper, whereas a cioAB mutant did not grow. Thus, P. aeruginosa relies on the CioAB enzyme to cope with severe copper deprivation. A quadruple cyo cco1 cco2 cox mutant, which was deleted for all known heme-copper terminal oxidases of P. aeruginosa, grew aerobically, albeit more slowly than did the wild type, indicating that the CioAB enzyme is capable of energy conservation. However, the expression of a cioA'-'lacZ fusion was less dependent on the copper status in the quadruple mutant than in the wild type, suggesting that copper availability might affect cioAB expression indirectly, via the function of the heme-copper oxidases.

Comprehensive approach for the detection of antifungal compounds using a susceptible strain of Candida albicans and confirmation of in vivo activity with the Galleria mellonella model.

An efficient screening strategy for the identification of potentially interesting low-abundance antifungal natural products in crude extracts that combines both a sensitive bioautography assay and high performance liquid chromatography (HPLC) microfractionation was developed. This method relies on high performance thin layer chromatography (HPTLC) bioautography with a hypersusceptible engineered strain of Candida albicans (DSY2621) for bioactivity detection, followed by the evaluation of wild type strains in standard microdilution antifungal assays. Active extracts were microfractionated by HPLC in 96-well plates, and the fractions were subsequently submitted to the bioassay. This procedure enabled precise localisation of the antifungal compounds directly in the HPLC chromatograms of the crude extracts. HPLC-PDA-mass spectrometry (MS) data obtained in parallel to the HPLC antifungal profiles provided a first chemical screening about the bioactive constituents. Transposition of the HPLC analytical conditions to medium-pressure liquid chromatography (MPLC) allowed the efficient isolation of the active constituents in mg amounts for structure confirmation and more extensive characterisation of their biological activities. The antifungal properties of the isolated natural products were evaluated by their minimum inhibitory concentration (MIC) in a dilution assay against both wild type and engineered strains of C. albicans. The biological activity of the most promising agents was further evaluated in vitro by electron microscopy and in vivo in a Galleria mellonella model of C. albicans infection. The overall procedure represents a rational and comprehensive means of evaluating antifungal activity from various perspectives for the selection of initial hits that can be explored in more in-depth mode-of-action studies. This strategy is illustrated by the identification and bioactivity evaluation of a series of antifungal compounds from the methanolic extract of a Rubiaceae plant, Morinda tomentosa, which was used as a model in these studies.

Composition, nanostructure, and optical properties of silver and silver-copper lusters

Lusters are composite thin layers of coinage metal nanoparticles in glass displaying peculiar optical properties and obtained by a process involving ionic exchange, diffusion, and crystallization. In particular, the origin of the high reflectance (golden-shine) shown by those layers has been subject of some discussion. It has been attributed to either the presence of larger particles, thinner multiple layers or higher volume fraction of nanoparticles. The object of this paper is to clarify this for which a set of laboratory designed lusters are analysed by Rutherford backscattering spectroscopy, transmission electron microscopy, x-ray diffraction, and ultraviolet-visible spectroscopy. Model calculations and numerical simulations using the finite difference time domain method were also performed to evaluate the optical properties. Finally, the correlation between synthesis conditions, nanostructure, and optical properties is obtained for these materials.

The use of micro-XRD for the study of glaze color decorations

The compounds responsible for the colours and decorations in glass and glazed ceramics include: colouring agents (transition metal ions), pigments (micro-and nano-precipitates of compounds that either do not dissolve or recrystallize in the glassy matrix) and opacifiers (microcrystalline compounds with high light scattering capability). Their composition, structure and range of stability are highly dependent not only on the composition but also on the procedures followed to obtain them. Chemical composition of the colorants and crystallites may be obtained by means of SEM-EDX and WDX. Synchrotron Radiation micro-X-ray Diffraction has a small beam size adequate (10 to 50 microns footprint size) to obtain the structural information of crystalline compounds and high brilliance, optimal for determining the crystallites even when present in low amounts. In addition, in glass decorations the crystallites often appear forming thin layers (from 10 to 100 micrometers thick) and they show a depth dependent composition and crystal structure. Their nature and distribution across the glass/glazes decorations gives direct information on the technology of production and stability and may be related to the color and appearance. A selection of glass and glaze coloring agents and decorations are studied by means of SR-micro- XRD and SEM-EDX including: manganese brown, antimony yellow, red copper lusters and cobalt blue. The selection includes Medieval (Islamic, and Hispano Moresque) and renaissance tin glazed ceramics from the 10th to the 17th century AD.

RpoN (sigma54) controls production of antifungal compounds and biocontrol activity in Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens CHA0 is an effective biocontrol agent of root diseases caused by fungal pathogens. The strain produces the antibiotics 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) that make essential contributions to pathogen suppression. This study focused on the role of the sigma factor RpoN (sigma54) in regulation of antibiotic production and biocontrol activity in P. fluorescens. An rpoN in-frame-deletion mutant of CHAO had a delayed growth, was impaired in the utilization of several carbon and nitrogen sources, and was more sensitive to salt stress. The rpoN mutant was defective for flagella and displayed drastically reduced swimming and swarming motilities. Interestingly, the rpoN mutant showed a severalfold enhanced production of DAPG and expression of the biosynthetic gene phlA compared with the wild type and the mutant complemented with monocopy rpoN+. By contrast, loss of RpoN function resulted in markedly lowered PLT production and plt gene expression, suggesting that RpoN controls the balance of the two antibiotics in strain CHA0. In natural soil microcosms, the rpoN mutant was less effective in protecting cucumber from a root rot caused by Pythium ultimum. Remarkably, the mutant was not significantly impaired in its root colonization capacity, even at early stages of root infection by Pythium spp. Taken together, our results establish RpoN for the first time as a major regulator of biocontrol activity in Pseudomonas fluorescens.

Fate of the herbicide glyphosate and its metabolite AMPA in soils and their transfer to surface waters: A multi-scale approach in the Lavaux vineyards, western Switzerland

The use of herbicides in agriculture may lead to environmental problems, such as surface water pollution, with a potential risk for aquatic organisms. The herbicide glyphosate is the most used active ingredient in the world and in Switzerland. In the Lavaux vineyards it is nearly the only molecule applied. This work aimed at studying its fate in soils and its transfer to surface waters, using a multi-scale approach: from molecular (10-9 m) and microscopic scales (10-6 m), to macroscopic (m) and landscape ones (103 m). First of all, an analytical method was developed for the trace level quantification of this widely used herbicide and its main by-product, aminomethylphosphonic acid (AMPA). Due to their polar nature, their derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) was done prior to their concentration and purification by solid phase extraction. They were then analyzed by ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The method was tested in different aqueous matrices with spiking tests and validated for the matrix effect correction in relevant environmental samples. Calibration curves established between 10 and 1000ng/l showed r2 values above 0.989, mean recoveries varied between 86 and 133% and limits of detection and quantification of the method were as low as 5 and 10ng/l respectively. At the parcel scale, two parcels of the Lavaux vineyard area, located near the Lutrive River at 6km to the east of Lausanne, were monitored to assess to which extent glyphosate and AMPA were retained in the soil or exported to surface waters. They were equipped at their bottom with porous ceramic cups and runoff collectors, which allowed retrieving water samples for the growing seasons 2010 and 2011. Results revealed that the mobility of glyphosate and AMPA in the unsaturated zone was likely driven by the precipitation regime and the soil characteristics, such as slope, porosity structure and layer permeability discrepancy. Elevated glyphosate and AMPA concentrations were measured at 60 and 80 cm depth at parcel bottoms, suggesting their infiltration in the upper parts of the parcels and the presence of preferential flow in the studied parcels. Indeed, the succession of rainy days induced the gradual saturation of the soil porosity, leading to rapid infiltration through macropores, as well as surface runoff formation. Furthermore, the presence of more impervious weathered marls at 100 cm depth induced throughflows, the importance of which for the lateral transport of the herbicide molecules was determined by the slope steepness. Important rainfall events (>10 mm/day) were clearly exporting molecules from the soil top layer, as indicated by important concentrations in runoff samples. A mass balance showed that total loss (10-20%) mainly occurred through surface runoff (96%) and, to a minor extent, by throughflows in soils (4%), with subsequent exfiltration to surface waters. Observations made in the Lutrive River revealed interesting details of glyphosate and AMPA dynamics in urbanized landscapes, such as the Lavaux vineyards. Indeed, besides their physical and chemical properties, herbicide dynamics at the catchment level strongly depend on application rates, precipitation regime, land use and also on the presence of drains or constructed channels. Elevated concentrations, up to 4970 ng/l, observed just after the application, confirmed the diffuse export of these compounds from the vineyard area by surface runoff during main rain events. From April to September 2011, a total load of 7.1 kg was calculated, with 85% coming from vineyards and minor urban sources and 15% from arable crops. Small vineyard surfaces could generate high concentrations of herbicides and contribute considerably to the total load calculated at the outlet, due to their steep slopes (~10%). The extrapolated total amount transferred yearly from the Lavaux vineyards to the Lake of Geneva was of 190kg. At the molecular scale, the possible involvement of dissolved organic matter (DOM) in glyphosate and copper transport was studied using UV/Vis fluorescence spectroscopy. Combined with parallel factor (PARAFAC) analysis, this technique allowed characterizing DOM of soil and surface water samples from the studied vineyard area. Glyphosate concentrations were linked to the fulvic-like spectroscopic signature of DOM in soil water samples, as well as to copper, suggesting the formation of ternary complexes. In surface water samples, its concentrations were also correlated to copper ones, but not in a significant way to the fulvic-like signature. Quenching experiments with standards confirmed field tendencies in the laboratory, with a stronger decrease in fluorescence intensity for fulvic-like fluorophore than for more aromatic ones. Lastly, based on maximum concentrations measured in the river, an environmental risk for these compounds was assessed, using laboratory tests and ecotoxicity data from the literature. In our case and with the methodology applied, the risk towards aquatic species was found negligible (RF<1).

Plant compounds insecticide activity against Coleoptera pests of stored products

The objective of this work was to screen plants with insecticide activity, in order to isolate, identify and assess the bioactivity of insecticide compounds present in these plants, against Coleoptera pests of stored products: Oryzaephilus surinamensis L. (Silvanidae), Rhyzopertha dominica F. (Bostrichidae) and Sitophilus zeamais Mots. (Curculionidae). The plant species used were: basil (Ocimum selloi Benth.), rue (Ruta graveolens L.), lion's ear (Leonotis nepetifolia (L.) R.Br.), jimson weed (Datura stramonium L.), baleeira herb (Cordia verbenacea L.), mint (Mentha piperita L.), wild balsam apple (Mormodica charantia L.), and billy goat weed or mentrasto (Ageratum conyzoides L.). The insecticide activity of hexane and ethanol extracts from those plants on R. dominica was evaluated. Among them, only hexane extract of A. conyzoides showed insecticide activity; the hexane extract of this species was successively fractionated by silica gel column chromatography, for isolation and purification of the active compounds. Compounds 5,6,7,8,3',4',5'-heptamethoxyflavone; 5,6,7,8,3'-pentamethoxy-4',5'-methilenedioxyflavone and coumarin were identified. However, only coumarin showed insecticide activity against three insect pests (LD50 from 2.72 to 39.71 mg g-1 a.i.). The increasing order of insects susceptibility to coumarin was R. dominica, S. zeamais and O. surinamensis.

Microbial communities in a porphyry copper tailings impoundment and their impact on the geochemical dynamics of the mine waste

The distribution and diversity of acidophilic bacteria of a tailings impoundment at the La Andina copper mine, Chile, was examined. The tailings have low sulfide (1.7% pyrite equivalent) and carbonate (1.4% calcite equivalent) contents and are stratified into three distinct zones: a surface (0-70-80 cm) `oxidation zone' characterized by low-pH (2.5-4), a `neutralization zone' (70-80 to 300-400 cm) and an unaltered `primary zone' below 400 cm. A combined cultivation-dependent and biomolecular approach (terminal restriction enzyme fragment length polymorphism and 16S rRNA clone library analysis) was used to characterize the indigenous prokaryotic communities in the mine tailings. Total cell counts showed that the microbial biomass was greatest in the top 125 cm of the tailings. The largest numbers of bacteria (10(9) g(-1) dry weight of tailings) were found at the oxidation front (the junction between the oxidation and neutralization zones), where sulfide minerals and oxygen were both present. The dominant iron-/sulfur-oxidizing bacteria identified at the oxidation front included bacteria of the genus Leptospirillum (detected by molecular methods), and Gram-positive iron-oxidizing acidophiles related to Sulfobacillus (identified both by molecular and cultivation methods). Acidithiobacillus ferrooxidans was also detected, albeit in relatively small numbers. Heterotrophic acidophiles related to Acidobacterium capsulatum were found by molecular methods, while another Acidobacterium-like bacterium and an Acidiphilium sp. were isolated from oxidation zone samples. A conceptual model was developed, based on microbiological and geochemical data derived from the tailings, to account for the biogeochemical evolution of the Piuquenes tailings impoundment.

Plant- and microbe-derived compounds affect the expression of genes encoding antifungal compounds in a pseudomonad with biocontrol activity.

We have investigated the impacts of 63 different low-molecular-weight compounds, most of them plant derived, on the in vitro expression of two antifungal biosynthetic genes by the plant-protecting rhizobacterium Pseudomonas fluorescens CHA0. The majority of the compounds tested affected the expression of one or both antifungal genes. This suggests that biocontrol activity in plant-beneficial pseudomonads is modulated by plant-bacterium signaling.

Latex production with depolymerizing compounds of actin cytoskeleton in rubber trees

The objective of this work was to assess stimulated latex flow from rubber trees (Hevea brasiliensis) with saturated macrolide (latrunculin A), 1, 5, and 10% potassium iodide in 2% methylcellulose compared with 0.3% ethylene in 2% methylcellulose (check) and 2% methylcellulose (blank). Latex output and contents of pure rubber, total solid, sucrose, inorganic phosphorus, thiol, and Mg2+ were measured. The treatments containing 1% KI or saturated macrolide increased latex yields compared to the blank with 2% methylcellulose alone. The 1% KI or saturated macrolide treatments were equal to that of 0.3% ethylene check treatment. However, 5 and 10% KI were harmful to bark of rubber trees, even caused prolonged tapping panel dryness.