Chemical Bioinduction of Rubber in Guayule Plant

mentioning

confidence: 99%

Stimulation of Isopentenyl Pyrophosphate Incorporation into Polyisoprene in Extracts from Guayule Plants (Parthenium argentatum Gray) by Low Temperature and 2-(3,4-Dichlorophenoxy) Triethylamine

Soundararajan¹,

Greenblatt²,

Foster³

et al. 1989

“…The effect of environmental conditions on this and growth generally are receiving attention (17), together with selection and breeding programs (18). A more recent approach however, is the use of bioregulators for chemical stimulation of rubber biosynthesis (11,24,29).…”

mentioning

confidence: 99%

Rubber Production in Guayule: Determination of Rubber Producing Potential

Macrae¹,

Gilliland²,

Staden³

1986

Optimum conditions for the rapid, efficient, nondestructive determination of rubber producing potential in guayule (Parthenium argentatum) were established. The rubber producing potential may be defined as the ability of the plant material to synthesize rubber from a precursor under specified conditions. To achieve this, stem slices taken from the first 5 centimeters of branches were incubated with I'4Clacetate as precursor in 0.1 molar phosphate buffer (pH 6.5) at 26°C for 16 hours in the light. The 14C from labeled acetate and acetyl coenzymeA were efficiently incorporated into rubber whereas the "C from both mevalonic acid (MVA) and isopentenylpyrophosphate (IPP) were poorly incorporated. Incorporation of 68.6% of the "C from labeled IPP into the acetone extractable material suggests that most of the IPP was channeled down the lower terpenoid branch of the polyisoprene biosynthetic pathway. The incorporation of "C from labeled acetate into rubber was most efficient at temperatures between 20 and 25°C. The rubber producing potential was also found to be dependent on light intensity. The roots which represent about one-third of the plant biomass not only had the highest rubber producing potential but also contained the highest amount of rubber (7.6%), indicating that the root system could be a major source of rubber. The mature stem bark also had a high rubber content and rubber producing potential, whereas the young stem had a low rubber content and a lower potential for producing rubber. The leaves showed little potential to incorporate labeled acetate into rubber and no more than 0.5% rubber was found in guayule leaves.

“…Recent investigations (8,20,22) on the chemical regulation of rubber biosynthesis in guayule (Parthenium argentatum Gray) suggest that rubber productivity can be improved by the use of substituted tertiary amines and could make this North American desert shrub an alternative to tropically grown Hevea brasiliensis as a source of natural rubber.…”

mentioning

confidence: 99%

“…induce rubber formation leads to an increase in MVA kinase, IPP isomerase, geranyl transferase, and rubber transferase (8). Gene derepression is involved in the induction of terpenoids by bioregulators (13,21).…”

mentioning

confidence: 99%

“…The addition of 0.4 millimolar dimethylallyl pyrophosphate to the rubber transferase reaction resulted in a 2-fold increase in the incorporation of IPP into rubber. A comparison was made of the relative activities of rubber transferase in different species of Parthenimm, Ficus, and Euphorbia.Recent investigations (8,20,22) Plant. Guayule seed (Parthenium argentatum A.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Isopentenyl Pyrophosphate cis-1,4-Polyisoprenyl Transferase from Guayule (Parthenium argentatum Gray)

Soundararajan¹,

Benedict²

1984

Electron micrographs of the mesophyll cells of guayule Parthenium argentatum Gry leaves show deposits of cis-polyisoprene (rubber) in the cytoplasm in the vicinity of mitochondria and chloroplasts and demonstrate that the rubber-synthesizing enzymes are present in guayule leaves. The terminal step in the synthesis of cis-polyisoprene from isopentenyl pyrophosphate (IPP) catalyzed by isopentenyl pyrophosphate cis-1,4-polyisoprenyl transferase has been demonstrated in crude leaf extracts by the enzymic incorporation of ['4Cjisopentenyl pyrophosphate into the polymer and the recovery of j'4Cjlevulinic acid following ozonolysis. The rubber transferase activity in the crude extracts of guayule leaves was 5.8 nanomoles isopentenyl pyrophosphate incorporated per milligram protein per hour. This is the first description of the rubber transferase from a nonlaticiferous plant.The specific activity (in units of nanomoles IPP converted per milligram protein per hour) of the partially purified enzyme following chromatography on diethylaminoethyl-cellulose columns was 41.7 units and contained 0.29 units of IPP isomerase activity and 0.08 units of farnesyl pyrophosphate synthetase activity. The rubber transferase requires reduced glutathione and Mg2" for maximal activity. There was no incorporation of IPP into cis-1,4-polyisoprene in the absence of rubber particles as primer, and Langmuir isotherm plots showed that the specific activity of the enzyme was proportional to the concentration ofthe enzyme on the surface of the rubber particles. For a given rubber particle distribution, enzyme activity was proportional to time, IPP concentration, and rubber concentration. The addition of 0.4 millimolar dimethylallyl pyrophosphate to the rubber transferase reaction resulted in a 2-fold increase in the incorporation of IPP into rubber. A comparison was made of the relative activities of rubber transferase in different species of Parthenimm, Ficus, and Euphorbia.Recent investigations (8,20,22) Plant. Guayule seed (Parthenium argentatum A. Gray) var 593 were soaked overnight in aerated H20. The seeds were germinated in small pots containing 2:1:1 (v/v/v) mixture of peat:perlite:vermiculite under fluorescent lamps at 25°C. Two weeks after germination, the seedlings were transplanted to large pots containing a 8:3:2 mixture of peat:perlite:vermiculite and grown in the greenhouse. The plants were kept well watered with distilled H20 and fertilized every 10 d with Peters 20-20-20 H20 soluble fertilizer and Peters S.T.E.M. Plants were sprayed with Isotox, Cygon, Plictran, and Diazanon for insect control.Electron Microscopy. Tissue from fully expanded leaves was placed in a paraformaldehyde-glutaraldehyde fixative in a sodium cacodylate buffer pH 7.2 and sliced into 1-mm segments. After 2 h, the tissue was washed in four 15-min changes of 0.05 M cacodylate buffer pH 7.2. The tissue was then postfixed in 2% OS04 in a cacodylate buffer pH 7.2 for 60 min. The leafsegments were once again rinsed in four 15-min changes of 0.05 M cacodylat...