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Kuswanhadi,Indonesian Rubber Research Institute | Leclercq J.,CIRAD - Agricultural Research for Development | Rio M.,CIRAD - Agricultural Research for Development | Tregear J.,IRD Montpellier | And 2 more authors.
Journal of Rubber Research | Year: 2010

Ethylene is a major stimulating factor for natural rubber production in Hevea brasiliensis and is often applied in the form of Ethephon, an ethylene releaser. In a positive feedback type mechanism, the application of ethylene leads to the enhanced expression of genes involved in ethylene biosynthesis such as ACC oxidases, which are also responsive to wounding. We studied the regulation of ethylene biosynthesis in rubber trees through the characterisation of the ACC oxidase multigene family and the responses of individual genes to ethylene and wounding. Three full-length cDNAs, HbACOl, HbAC02 and HbAC03, were isolated. The HbACOs were 1115, 1174 and 1074 bp long, respectively, with open reading frames encoding polypeptides of 312, 318 and 318 amino acids, respectively. The genomic sequences of HbACOl andHbkC02 were also characterised, revealing divergent gene structures: HbACOl (1456 bp) possesses three introns andfour exons, while HbAC02 (1418 bp) consists of two introns and three exons. All of the HbACO genes were expressed at all stages of development studied, from in vitro callus to the exploited plant, but with different expression profiles. Nevertheless, no expression was detected in latex. In the bark of the shoot of the first flush of budded plants, HbACOl was expressed at a higher level than the other genes, and was down-regulated by ethylene and wounding in both leaf and bark tissues. In contrast, HbAC02 and HbAC03 were transiently induced in response to ethylene and wounding. Treatment with 1-MCP, an ethylene action inhibitor, abolished the ethylene induction ofHbAC02 gene, showing that this gene was under positive feedback regulation. The expression of HbAC03 gene was also induced by ethylene treatment and wounding, again with an antagonistic effect of 1-MCP. In conclusion, HbACOl appears to be responsible for basal levels of ethylene production while HbAC02 and HbAC03 are up-regulated in response to external factors. Source


Fathurrohman M.I.,Indonesian Rubber Research Institute | Soegijono B.,University of Indonesia | Budianto E.,University of Indonesia | Ramadhan A.,Indonesian Rubber Research Institute
Macromolecular Symposia | Year: 2015

Summary Rubber nanocomposites based on the natural rubber (NR) and organically modified montmorillonite (OMMT) were prepared by melt intercalation technique using a laboratory open mill followed by compression molding. Organically modified organoclays with different d-spacing were added to the natural rubber matrix to examine the influence of d-spacing of organoclay on morphology, curing characteristic and mechanical property of nanocomposite. The characterizations were carried out by means of X-ray diffraction, scanning electron, atomic force microscopy and moving die rheometer. The results show that melt mixing by an open mill is an effective method for dispersing OMMT throughout the natural rubber matrix especially for organoclay cloisite 15A whose d-spacing is high and well dispersed in natural rubber matrix. The hardness and stresses at low strain of NR/organoclay nanocomposites slightly increased with increasing d-spacing of organoclay, but elongation at break decreased. The swelling behavior of NR/organoclay nanocomposite improved with increasing d-spacing of organoclay. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Sari T.I.,University of Indonesia | Saputra A.H.,University of Indonesia | Bismo S.,University of Indonesia | Maspanger D.R.,Indonesian Rubber Research Institute | Cifriadi A.,Indonesian Rubber Research Institute
International Journal of Technology | Year: 2015

Graft copolymerization of an acrylonitrile monomer onto Deproteinized Natural Rubber (DPNR) is an important process in the modification of Natural Rubber (NR) to increase its oil resistance. However, coagulation at the beginning of the process was a problem causing a copolymerization foil to occur. The presence of a styrene monomer is therefore expected to improve the emulsion condition so that coagulation can be prevented in the early reaction step. For comparison purposes, the processes with and without styrene were investigated. The influence of the concentration of styrene as well as the ratio of the DPNR:monomer on the stabilization process were also observed. The results showed that the addition of styrene could improve the stabilization process as proven by Fourier Transform Infrared Spectroscopy (FTIR). The presence of the functional group of C≡N at FTIR proved the production of the polyacrylonitrile in the mixture. The investigation showed that the concentration of styrene monomer, which led to the emulsion stability, is up to 1.5 wt% concentration of styrene at the ratio of DPNR:monomer (M) of 70:30 wt%. © IJTech 2015. Source


Piyatrakul P.,CIRAD - Agricultural Research for Development | Piyatrakul P.,Rubber Research Institute | Yang M.,CAS Beijing Institute of Genomics | Putranto R.-A.,CIRAD - Agricultural Research for Development | And 9 more authors.
PLoS ONE | Year: 2014

The AP2/ERF superfamily encodes transcription factors that play a key role in plant development and responses to abiotic and biotic stress. In Hevea brasiliensis, ERF genes have been identified by RNA sequencing. This study set out to validate the number of HbERF genes, and identify ERF genes involved in the regulation of latex cell metabolism. A comprehensive Hevea transcriptome was improved using additional RNA reads from reproductive tissues. Newly assembled contigs were annotated in the Gene Ontology database and were assigned to 3 main categories. The AP2/ERF superfamily is the third most represented compared with other transcription factor families. A comparison with genomic scaffolds led to an estimation of 114 AP2/ERF genes and 1 soloist in Hevea brasiliensis. Based on a phylogenetic analysis, functions were predicted for 26 HbERF genes. A relative transcript abundance analysis was performed by real-time RT-PCR in various tissues. Transcripts of ERFs from group I and VIII were very abundant in all tissues while those of group VII were highly accumulated in latex cells. Seven of the thirty-five ERF expression marker genes were highly expressed in latex. Subcellular localization and transactivation analyses suggested that HbERF-VII candidate genes encoded functional transcription factors. Source


Kumoro A.C.,Diponegoro University | Nasution D.A.,Indonesian Center for Agricultural Engineering Research and Development | Cifriadi A.,Indonesian Rubber Research Institute | Purbasari A.,Diponegoro University | Falaah A.F.,Indonesian Rubber Research Institute
International Journal of Applied Engineering Research | Year: 2014

This work aimed to determine the minimum fluidization velocity of biomass and river sand particles mixtures at various biomass mass fractions in the range of 0 to 1. Mixtures of river sand and rice husk or corn cob particles were chosen to represent mixtures of particles with different size, density and shape. Based on the experimental data obtained from the present work and those found in the literatures, a new correlation was developed to predict the minimum fluidization velocity for biomass and sand mixtures in terms of sphericity, Reynolds and Archimedes numbers. Further, it was found that the minimum fluidization velocity based on Archimedes number of biomass and sand particles mixture depends on the average sphericity of particles mixturesand the corresponding Reynolds number. The sphericity of the biomass and sand particles mixture affects Archimedes number of the mixture significantly in the laminar region, but does not affect the Archimedes number in the intermediate region. The predictions agree fairly well with the reported experimental and literatures data in the range of 1˂Re˂50, which cover both laminar and intermediate flows regions. This newly developed correlation is also applicable for the prediction of minimum fluidization velocity of inert or biomass particles only by setting the mass fraction to be 0 or 1 accordingly. © Research India Publications. Source

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