Molecular biochemical characterization of rubber biosynthetic machinery in Hevea and Dandelion, and evaluation of Rabbitbrush as a potential domestic rubber crop
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Authors
Hathwaik, Upul I.
Issue Date
2012
Type
Dissertation
Language
Keywords
Biofuel , Dandelion , Hevea , Rabbitbrush , Rubber , Rubber transferase
Alternative Title
Abstract
Natural rubber is an irreplaceable material that is used in manufacturing over
40,000 products including tires and numerous medical devices. Hevea brasiliensis is the
sole producer of world natural rubber and more than 90% of the Hevea plantations are
located in less than five South Asian countries. In 2011, the US spent 4.4 billion dollars
to import natural rubber. When considering the unpredictability and high cost of NR
imports, the limited growing conditions of Hevea plants, the increasing allergic reactions
caused by Hevea rubber, and the irreplaceability by synthetics, it is clear that domestic
sources of natural rubber are needed. Furthermore, the rubber transferase that is
responsible for producing rubber is currently unknown, and understanding rubber
biosynthetic pathway will help to improve domestic rubber crops. In this study several
experiments were done to identify the rubber transferase. The rubber transferase is
responsible for the polymerization of isopentenyl pyrophosphate (IPP) monomers into
high molecular weight cis-1,4-polyisoprene polymer with the help of farnesyl
pyrophosphate (FPP) primer. In all rubber producing plants rubber is made in cytosolic
compartments know as rubber particles. The analyses of H. brasiliensis rubber particle
proteins with liquid chromatography mass spectrometry (LC/MS) and western blot
analysis using cis-prenyltransferase (CPT) antibodies confirmed the CPT localization in
washed rubber particles (WRPs). Direct evidence of CPT involvement in rubber
polymerization was established by in vitro cross-linking studies done with two different
FPP analogues. The in vivo role of CPT was identified by CPT under-expressing
transgenic Taraxacum kok-saghyz (Russian Dandelion) plants.
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Additionally, this research was focused in identifying a domestic rubber crop.
Ericameria nauseosa (Rabbitbrush) is one of the very few domestic rubber producers.
Wild Rabbitbrush populations were analyzed for their rubber amount and molecular
weight. Patterns of rubber accumulation and molecular weight in shoots with different
diameter tissue were established over time. Rabbitbrush collected from Austin, NV had
high quality rubber in high yield. The extracted rubber had several physical properties
that were analogous to existing commercial natural rubber producers. The resins and the
biomass of Rabbitbrush were also analyzed. Both resin and leftover biomass residue had
promising characteristics. Overall, Rabbitbrush collected from Austin, NV has the
potential of becoming a domestic natural rubber, resin, and biomass crop.
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In Copyright(All Rights Reserved)