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Hevea Brasiliensis (hevea + brasiliensi)
Selected AbstractsLocal hydrologic effects of introducing non-native vegetation in a tropical catchmentECOHYDROLOGY, Issue 1 2008Maite Guardiola-Claramonte Abstract This study investigates the hydrologic implications of land use conversion from native vegetation to rubber (Hevea brasiliensis) in Southeast Asia. The experimental catchment, Nam Ken (69 km2), is located in Xishuangbanna Prefecture (22°N, 101°E), in the south of Yunnan province, in southwestern China. During 2005 and 2006, we collected hourly records of 2 m deep soil moisture profiles in rubber and three native land-covers (tea, secondary forest and grassland), and measured surface radiation above the tea and rubber canopies. Observations show that root water uptake of rubber during the dry season is controlled by day-length, whereas water demand of the native vegetation starts with the arrival of the first monsoon rainfall. The different dynamics of root water uptake in rubber result in distinct depletion of soil moisture in deeper layers. Traditional evapotranspiration and soil moisture models are unable to simulate this specific behaviour. Therefore, a different conceptual model, taking in account vegetation dynamics, is needed to predict hydrologic changes due to land use conversion in the area. Copyright © 2008 John Wiley & Sons, Ltd. [source] Molecular cloning, expression and characterization of cDNA encoding cis -prenyltransferases from Hevea brasiliensisFEBS JOURNAL, Issue 23 2003A key factor participating in natural rubber biosynthesis Natural rubber from Hevea brasiliensis is a high molecular mass polymer of isoprene units with cis -configuration. The enzyme responsible for the cis -1,4-polymerization of isoprene units has been idengified as a particle-bound rubber transferase, but no gene encoding this enzyme has been cloned from rubber-producing plants. By using sequence information from the conserved regions of cis -prenyl chain elongating enzymes that were cloned recently, we have isolated and characterized cDNAs from H. brasiliensis for a functional factor participating in natural rubber biosynthesis. Sequence analysis revealed that all of the five highly conserved regions among cis -prenyl chain elongating enzymes were found in the protein sequences of the Hevea cis -prenyltransferase. Northern blot analysis indicated that the transcript(s) of the Hevea cis -prenyltransferase were expressed predominantly in the latex as compared with other Hevea tissues examined. In vitro rubber transferase assays using the recombinant gene product overexpressed in Escherichia coli revealed that the enzyme catalyzed the formation of long chain polyprenyl products with approximate sizes of 2 × 103,1 × 104 Da. Moreover, in the presence of washed bottom fraction particles from latex, the rubber transferase activity producing rubber product of high molecular size was increased. These results suggest that the Hevea cis -prenyltransferase might require certain activation factors in the washed bottom fraction particles for the production of high molecular mass rubber. [source] Protein farnesyltransferase inhibitors interfere with farnesyl diphosphate binding by rubber transferaseFEBS JOURNAL, Issue 19 2003Christopher J. D. Mau Rubber transferase, a cis -prenyltransferase, catalyzes the addition of thousands of isopentenyl diphosphate (IPP) molecules to an allylic diphosphate initiator, such as farnesyl diphosphate (FPP, 1), in the presence of a divalent metal cofactor. In an effort to characterize the catalytic site of rubber transferase, the effects of two types of protein farnesyltransferase inhibitors, several chaetomellic acid A analogs (2, 4,7) and ,-hydroxyfarnesylphosphonic acid (3), on the ability of rubber transferase to add IPP to the allylic diphosphate initiator were determined. Both types of compounds inhibited the activity of rubber transferases from Hevea brasiliensis and Parthenium argentatum, but there were species,specific differences in the inhibition of rubber transferases by these compounds. Several shorter analogs of chaetomellic acid A did not inhibit rubber transferase activity, even though the analogs contained chemical features that are present in an elongating rubber molecule. These results indicate that the initiator-binding site in rubber transferase shares similar features to FPP binding sites in other enzymes. [source] Potential active-site residues in polyneuridine aldehyde esterase, a central enzyme of indole alkaloid biosynthesis, by modelling and site-directed mutagenesisFEBS JOURNAL, Issue 12 2002Emine Mattern-Dogru In the biosynthesis of the antiarrhythmic alkaloid ajmaline, polyneuridine aldehyde esterase (PNAE) catalyses a central reaction by transforming polyneuridine aldehyde into epi-vellosimine, which is the immediate precursor for the synthesis of the ajmalane skeleton. The PNAE cDNA was previously heterologously expressed in E. coli. Sequence alignments indicated that PNAE has a 43% identity to a hydroxynitrile lyase from Hevea brasiliensis, which is a member of the ,/, hydrolase superfamily. The catalytic triad, which is typical for this family, is conserved. By site-directed mutagenesis, the members of the catalytic triad were identified. For further detection of the active residues, a model of PNAE was constructed based on the X-ray crystallographic structure of hydroxynitrile lyase. The potential active site residues were selected on this model, and were mutated in order to better understand the relationship of PNAE with the ,/, hydrolases, and as well its mechanism of action. The results showed that PNAE is a novel member of the ,/, hydrolase enzyme superfamily. [source] Expression and characterization of active site mutants of hevamine, a chitinase from the rubber tree Hevea brasiliensisFEBS JOURNAL, Issue 3 2002Evert Bokma Hevamine is a chitinase from the rubber tree Hevea brasiliensis. Its active site contains Asp125, Glu127, and Tyr183, which interact with the ,1 sugar residue of the substrate. To investigate their role in catalysis, we have successfully expressed wild-type enzyme and mutants of these residues as inclusion bodies in Escherichia coli. After refolding and purification they were characterized by both structural and enzyme kinetic studies. Mutation of Tyr183 to phenylalanine produced an enzyme with a lower kcat and a slightly higher Km than the wild-type enzyme. Mutating Asp125 and Glu127 to alanine gave mutants with ,,2% residual activity. In contrast, the Asp125Asn mutant retained substantial activity, with an approximately twofold lower kcat and an approximately twofold higher Km than the wild-type enzyme. More interestingly, it showed activity to higher pH values than the other variants. The X-ray structure of the Asp125Ala/Glu127Ala double mutant soaked with chitotetraose shows that, compared with wild-type hevamine, the carbonyl oxygen atom of the N -acetyl group of the ,1 sugar residue has rotated away from the C1 atom of that residue. The combined structural and kinetic data show that Asp125,and Tyr183 contribute to catalysis by positioning the,carbonyl oxygen of the N -acetyl group near to the C1 atom. This allows the stabilization of a positively charged transient intermediate, in agreement with a previous proposal that the enzyme makes use of substrate-assisted catalysis. [source] Hev b 9, an enolase and a new cross-reactive allergen from Hevea latex and moldsFEBS JOURNAL, Issue 24 2000Purification, characterization, cloning, expression Natural rubber latex allergy is an IgE-mediated disease that is caused by proteins that elute from commercial latex products. A complementary DNA (cDNA) coding for Hev b 9, an enolase (2-phospho- d -glycerate hydrolyase) and allergen from latex of the rubber tree Hevea brasiliensis, was amplified by PCR. The PCR primers were designed according to conserved regions of enolases from plants. The obtained cDNA amplification product consisted of 1651 bp and encoded a protein of 445 amino-acid residues with a calculated molecular mass of 47.6 kDa. Sequence comparisons revealed high similarities of the Hevea latex enolase to mold enolases that have been identified as important allergens. In addition, the crucial amino-acid residues that participate in the formation of the catalytic site and the Mg2+ binding site of enolases were also conserved. Hevea latex enolase was produced as a recombinant protein in Escherichia coli with an N-terminal hexahistidyl tag, and purified by affinity chromatography. The yield amounted to 110 mg of purified Hev b 9 per litre of bacterial culture. The recombinant allergen bound IgE from latex, as well as mold-allergic patients, in immunoblot and ELISA experiments. The natural enolase was isolated from Hevea latex by (NH4)2SO4 precipitation and ion exchange chromatography. The natural and the recombinant (r)Hev b 9 showed equivalent enzymatic activity. Patients' IgE-antibodies preincubated with rHev b 9 lost their ability to bind to natural (n) Hev b 9, indicating the identity of the B-cell epitopes on both molecules. Cross-reactivity with two enolases from Cladosporium herbarum and Alternaria alternata was determined by inhibition of IgE-binding to these enolases by rHev b 9. Therefore, enolases may represent another class of highly conserved enzymes with allergenic potentials. [source] Rubber tree (Hevea brasiliensis) trunk phloem necrosis: aetiological investigations failed to confirm any biotic causal agentFOREST PATHOLOGY, Issue 1 2007F. Pellegrin Summary Trunk phloem necrosis (TPN) is currently a main constraint in rubber (Hevea brasiliensis) plantations. The apparent spread of the disease, from tree to tree along the planting line, strongly supported the implication of a pathogen that could be transmitted mechanically via the tapping knife. In order to detect a causal agent of the disease, studies focusing on characterization of the known mechanically transmitted pathogens (e.g. viroids, cryptic viruses or phytoplasma) were initiated. RNA strands of low molecular weight (200,400 and >500 bp) displaying structural similarities with viroids and viral dsRNAs were observed in various tested samples. However, attempts to show the potential role of these RNA molecules in the spread of the disease failed. First of all, there was no significant or reproducible correlation between the health status of the rubber trees sampled and these RNA molecules. Moreover, no sequence homology with known pathogens could be found when randomly amplified cDNA fragments isolated from trees presenting the disease symptoms were sequenced. In conclusion, the aetiological investigations, in order to show the presence of a pathogen responsible of the TPN disease, were non-conclusive, which tends to disprove the hypothesis of a biotic causal agent. [source] Monoterpene emissions from rubber trees (Hevea brasiliensis) in a changing landscape and climate: chemical speciation and environmental controlGLOBAL CHANGE BIOLOGY, Issue 11 2007YONG-FENG WANG Abstract Emissions of biogenic volatile organic compounds (VOCs) have important roles in ecophysiology and atmospheric chemistry at a wide range of spatial and temporal scales. Tropical regions are a major global source of VOC emissions and magnitude and chemical speciation of VOC emissions are highly plant-species specific. Therefore it is important to study emissions from dominant species in tropical regions undergoing large-scale land-use change, for example, rubber plantations in South East Asia. Rubber trees (Hevea brasiliensis) are strong emitters of light-dependent monoterpenes. Measurements of emissions from leaves were made in the dry season in February 2003 and at the beginning of the wet season in May 2005. Major emitted compounds were sabinene, , -pinene and , -pinene, but , -ocimene and linalool also contributed significantly at low temperature and light. Cis -ocimene was emitted with a circadian course independent of photosynthetic active radiation (PAR) and temperature changes with a maximum in the middle of the day. Total isoprenoid VOC emission potential at the beginning of the wet season (94 ,g gdw,1 h,1) was almost two orders of magnitude higher than measured in the dry season (2 ,g g dw,1 h,1). Composition of total emissions changed with increasing temperature or PAR ramps imposed throughout a day. As well as light and temperature, there was evidence that assimilation rate was also a factor contributing to seasonal regulating emission potential of monoterpenes from rubber trees. Results presented here contribute to a better understanding of an important source of biogenic VOC associated with land-use change in tropical South East Asia. [source] Highly purified natural rubber by saponificaion of latex: Analysis of green and cured propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Sureerut Amnuaypornsri Abstract Natural rubber (NR) was purified by saponification of fresh latex from Hevea brasiliensis and soaking process of the coagulum with aqueous NaOH solution. This treatment resulted in the decrease of nitrogen content to the same level as enzymatic deproteinized NR. The saponification of NR latex and soaking of the coagulum gave the rubber having good processability with easy to cure. The saponified rubber showed outstanding physical and dynamic mechanical properties such as high tensile properties, high storage modulus, low tan ,, low heat build-up and low dynamic compression set. The saponified rubber blend with styrene butadiene rubber (SBR) according to the recipe of rubber tire showed also a good performance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Character of long-chain branching in highly purified natural rubberJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Sureerut Amnuaypornsri Abstract The nature of long-chain branching in natural rubber (NR) from Hevea brasiliensis was analyzed for NR purified by enzymatic deproteinization in the latex state followed by acetone extraction in the solid state to remove the proteins and neutral lipids, respectively. The treatment of purified NR in a toluene solution with a polar solvent, such as methanol or acetic acid, resulted in a clear decrease in the molecular weight, gel content, and Huggins' constant; this was caused by the decomposition of branch points in the purified rubber. This finding clearly showed that long-chain branching in the purified NR was mainly derived from the association of phospholipids linked with both terminal groups in the rubber chain via hydrogen bonds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] In vitro Transient Expression System of Latex C-serum was used for Analysis of Hevein Promoter in Response to Abscisic Acid in Hevea brasiliensisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 3 2008Xiao-Wen Fei Abstract Hevein has been found to be an essential element in coagulation of rubber particles in latex of rubber trees. In a previous study, we cloned a 1 241-bp fragment of a 5, upstream region of the hevein gene by genome walking. This fragment was analyzed by a 5, end nested deletion method in the present study, fused with a uidA (gus) gene to produce a series of tested constructs, which were transferred into C-serum of latex and the Gus activities were detected. Results showed that the fragment from ,749 to ,292 was sufficient for expression of gus gene in latex, and the fragment from ,292 to ,168 was crucial in response to abscisic acid inducement. In a transient transgenic test of rubber leaf with particle bombardment, construct Hev749 conferred gus -specific expression in veins, in which the latex tubes mainly distributed. This implies that the fragment from ,749 to ,292 was laticiferous-specific. [source] Defence Responses of Calli and Seeds of Hevea brasiliensis to Zoospores and the Elicitin of Phytophthora palmivoraJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2008Nion Chirapongsatonkul Abstract The defence responses of calli and seeds of two cultivars (resistant; BPM-24 and susceptible; RRIM600) of the rubber tree, Hevea brasiliensis, against zoospores and elicitin purified from its pathogen, Phytophthora palmivora, were investigated. Both zoospores and elicitin induced the biosynthesis of the phytoalexin, scopoletin (Scp), in Hevea calli ranging from 5 × 105 to 4.5 × 106 zoospores/ml and 0.5 to 2 ,g elicitin/g fresh weight of calli. At the highest concentration of zoospores (4.5 × 106 zoospores/ml) or elicitin (2 ,g/g fresh weight of calli), the rate of Scp production was fastest but then it rapidly decreased and produced lower peak value than detected at the optimum concentration. The decline of Scp level at the highest zoospore/elicitin concentration was correlated to the amount of cell death measured by Evans Blue method. Peroxidase (POD) activities in Hevea calli were also measured using the optimum level of zoospores or elicitin. Induction of Scp preceded the production of Scp POD and o -dianisidine POD then followed by the guaiacol POD. The Scp and POD accumulations were approximately two to three times higher in the resistance cultivar than those in the susceptible one. As the responses of the calli to elicitin were faster than those to the zoospores, it demonstrates that zoospores require more time to act on the host cells. The pattern of Scp and POD activities monitored in elicitin-treated Hevea seeds was similar to that of Hevea calli after treating with zoospores or elicitin. Therefore, the callus cultures could be used as a tool for studying other defence mechanisms in H. brasiliensis. The achieved knowledge will be applied to enhance resistance and led to the protection of Hevea young seedlings from the pathogen in the plantation. [source] Micropropagation of self-rooting juvenile clones by secondary somatic embryogenesis in Hevea brasiliensisPLANT BREEDING, Issue 2 2010Y. W. Hua With 2 figures and 5 tables Abstract Micropropagation of self-rooting juvenile clones in Hevea brasiliensis was established for two clones CATAS 7-33-97 and CATAS 88-13 through the following three steps: induction of primary embryos, embryo multiplication by secondary somatic embryogenesis in three successive cycles from a single culture of primary embryo and plant regeneration. The embryo multiplication coefficients of the two clones increased in the first cycle and reached the maximum in the second and the third cycle at the same rate. Significant effects of origins of embryo fragments and calcium on secondary embryogenesis were detected, the highest ratios of the regenerated embryos to primary embryos appeared, when embryo fragments close to the base of embryos were used and incubated in Murashige and Skoog (MS)-based callogenesis medium with 6.0 mm CaCl2 for CATAS 88-13 and 9.0 mm CaCl2 for CATAS 7-33-97. The highest rates of plant conversion were produced on MS-based plant regeneration medium with 4.5 and 9.0 ,m 2,4-D for CATAS 7-33-97 (85.0%) and 13.5 ,m for CATAS 88-13 (75.0%), being higher than other reports (60%). Finally, the application of this system was discussed. [source] Microsatellite variability and its use in the characterization of cultivated clones of Hevea brasiliensisPLANT BREEDING, Issue 1 2005T. Saha Abstract Microsatellite markers were developed and evaluated in Hevea brasiliensis, an important crop species producing natural rubber of commercial utility. Of eight microsatellite markers, four were found to be highly informative, amplifying a total of 19 alleles when evaluated against 27 cultivated Hevea clones/genotypes. Power of discrimination of the microsatellite loci was in the range of 0.62-0.89, with a mean of 0.76 indicating these microsatellites could be valuable genetic markers for diversity characterization. A combination of four microsatellite markers was successfully used to discriminate uniquely all the 27 Hevea clones and some clone-specific allelic profiles were generated. Cross-species amplification of the markers developed in H. brasiliensis had also been demonstrated with two other Hevea species, H. benthamiana and H. spruceana, indicating a high degree of sequence homology at the flanking regions. Sequence analysis of the repeat region at the 3,-UTR of the hydroxymethylglutaryl-coenzyme A reductase gene, containing clusters of AG repeats in 15 clones, revealed the existence of two alleles based on the repeat length polymorphisms. Homozygosity as well as heterozygosity for both the alleles had also been detected among the clones. Frequency of homozygotes for the smaller allele (allele-1) was found to be lower than the larger allele (allele-2) among the primary clones of H. brasiliensis. [source] First report of Inonotus rickii causing canker and decay on Hevea brasiliensis in ChinaPLANT PATHOLOGY, Issue 4 2010Y. C. Dai No abstract is available for this article. [source] The active site of hydroxynitrile lyase from Prunus amygdalus: Modeling studies provide new insights into the mechanism of cyanogenesisPROTEIN SCIENCE, Issue 2 2002Ingrid Dreveny Abstract The FAD-dependent hydroxynitrile lyase from almond (Prunus amygdalus, PaHNL) catalyzes the cleavage of R -mandelonitrile into benzaldehyde and hydrocyanic acid. Catalysis of the reverse reaction,the enantiospecific formation of ,-hydroxynitriles,is now widely utilized in organic syntheses as one of the few industrially relevant examples of enzyme-mediated C,C bond formation. Starting from the recently determined X-ray crystal structure, systematic docking calculations with the natural substrate were used to locate the active site of the enzyme and to identify amino acid residues involved in substrate binding and catalysis. Analysis of the modeled substrate complexes supports an enzymatic mechanism that includes the flavin cofactor as a mere "spectator" of the reaction and relies on general acid/base catalysis by the conserved His-497. Stabilization of the negative charge of the cyanide ion is accomplished by a pronounced positive electrostatic potential at the binding site. PaHNL activity requires the FAD cofactor to be bound in its oxidized form, and calculations of the pKa of enzyme-bound HCN showed that the observed inactivation upon cofactor reduction is largely caused by the reversal of the electrostatic potential within the active site. The suggested mechanism closely resembles the one proposed for the FAD-independent, and structurally unrelated HNL from Hevea brasiliensis. Although the actual amino acid residues involved in the catalytic cycle are completely different in the two enzymes, a common motif for the mechanism of cyanogenesis (general acid/base catalysis plus electrostatic stabilization of the cyanide ion) becomes evident. [source] Quantitative analysis of immunoglobulin E reactivity profiles in patients allergic or sensitized to natural rubber latex (Hevea brasiliensis)CLINICAL & EXPERIMENTAL ALLERGY, Issue 11 2007M. Raulf-Heimsoth Summary Background Characterized native and recombinant Hevea brasiliensis (rHev b) natural rubber latex (NRL) allergens are available to assess patient allergen sensitization profiles. Objective Quantification of individual IgE responses to the spectrum of documented NRL allergens and evaluation of cross-reactive carbohydrate determinants (CCDs) for more definitive diagnosis. Methods Sera of 104 healthcare workers (HCW; 51 German, 21 Portuguese, 32 American), 31 spina bifida patients (SB; 11 German, 20 Portuguese) and 10 Portuguese with multiple surgeries (MS) were analysed for allergen-specific IgE antibody (sIgE) to NRL, single Hev b allergens and CCDs with ImmunoCAPÔ technology. Results In all patient groups rHev b 5-sIgE concentrations were the most pronounced. Hev b 2, 5, 6.01 and 13 were identified as the major allergens in HCW and combined with Hev b 1 and Hev b 3 in SB. In MS Hev b 1 displayed an intermediate relevance. Different sIgE antibody levels to native Hevea brasiliensis (nHev b) 2 and rHev b 6.01 allowed discrimination of SB with clinical relevant latex allergy vs. those with latex sensitization. Sensitization profiles of German, Portuguese and American patients were equivalent. rHev b 5, 6.01 and nHev b 13 combined detected 100% of the latex-allergic HCW and 80.1% of the SB. Only 8.3% of the sera showed sIgE response to CCDs. Conclusions Hev b 1, 2, 5, 6.01 and 13 were identified as the major Hev b allergens and they should be present in standardized latex extracts and in vitro allergosorbents. CCDs are only of minor relevance in patients with clinical relevant latex allergy. Component-resolved diagnostic analyses for latex allergy set the stage for an allergen-directed immunotherapy strategy. [source] Latex allergy: low prevalence of immunoglobulin E to highly purified proteins Hev b 2 and Hev b 13CLINICAL & EXPERIMENTAL ALLERGY, Issue 10 2007T. Palosuo Summary Background Hevea brasiliensis (Hev b) 2 and Hev b 13 have recently been identified as major latex allergens by detecting specific IgE antibodies in >50% of sera from Hev b latex-allergic individuals. Objective We assessed the prevalence rates for sensitization to extensively purified latex allergens in patients from three diverse geographical areas. Methods Native Hev b 2, Hev b 5, Hev b 6.01 and Hev b 13 were purified by non-denaturating chromatography and were used in ELISAs to assess sera from 215 latex-allergic patients and 172 atopic non-sensitized controls from Finland, Spain and the United States to detect allergen-specific IgE antibodies. Results Unexpectedly, even highly purified Hev b 13 contained epitope(s) to which Hev b 6-specific human IgE antibodies bound effectively. Further purification, however, reduced the prevalence of IgE antibody reactivity to low levels: 15%, 5% and 11% for Hev b 2, and 18%, 30% and 27% for Hev b 13 among latex-allergic Finnish, Spanish and American patients, respectively. Interestingly, Finnish patients had a lower prevalence of Hev b 5-specific IgE antibody (28%) as compared with Spanish (49%) and American (71%) patients. The prevalence of Hev b 6.01-specific IgE reactivity was uniformly >50% in all three populations. Conclusion Neither Hev b 2 nor Hev b 13 appear to be major latex allergens when evaluated in serological assays using highly purified allergens. The reason(s) for the observed differences in published sensitization rates in various geographic regions requires further study. The purity of the allergen preparations has a marked impact on the accuracy of latex-specific IgE antibody detection in epidemiological studies and in the serological diagnosis of latex allergy. [source] Enhanced solvent extraction of polar lipids associated with rubber particles from hevea brasiliensisPHYTOCHEMICAL ANALYSIS, Issue 2 2007Frederic Bonfils Abstract Biochemical studies of lipids bound to rubber particles have been complicated due to the solubility of polyisoprene chains in most extracting solvents and the rather delicate nature of polar lipids that are often denatured when traditional solvent extraction techniques are employed. In this paper, we describe a traditional technique and accompanying solvents that permit optimal extraction of rubber particle bound lipids. The technique, which is validated after characterizing the lipid extracts by elemental analysis, silica column adsorption and thin layer chromatography, appeared more suitable for extracting total lipids with optimal glycolipid and phospholipid contents. This technique is proposed as an alternative to traditional extraction methods used for solid natural rubber as it offers advantages with respect to ease of application, extract quality, extraction yields and reproducibility. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||