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

Abstract

Rubber particles isolated from guayule (Parthenium argentatum Gray) stem homogenates contain a polyprenyl transferase which catalyzes the polymerization of isopentenyl pyrophosphate into polyisoprene. The polymerization reaction is stimulated with the addition of an allylic pyrophosphate initiator and forms a polymer of polyisoprene with a molecular weight distribution from 103 to 107. The

Seasonal Variations in Rubber Biosynthesis, 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase, and Rubber Transferase Activities in Parthenium argentatum in the Chihuahuan Desert

“…Rubber transferase activity has been characterized in crude homogenates of guayule stems and is stimulated 12-fold by the low temperatures of the fall and winter in the Chihuahuan Desert (Madhavan et al, 1988). HMGR activity has been studied in the membrane fraction of the latex of H. brasiliensis (Sipat, 1985) but has not been characterized in stem tissues from guayule plants.…”

“…IPP isomerase activity in the homogenates of the bark from the lower stem was determined by the procedures of Scatterwhite (1985) and Madhavan et al (1988). The reaction mixtures contained 1.2 pmol of MgC12, 1.8 pmol of potassium fluoride, 0.75 pmol of GSH, pH 8.0, 27 nmol of [l-'*C]IPP containing 30.5 X 106 cpm of radioactivity, and 90 WL of the crude homogenate to a final volume of 150 pL.…”

“…chains catalyzed by a rubber transferase bound to rubber particles is the same in both species (Archer and Audley, 1987;Madhavan et al, 1988), but an outstanding feature of rubber formation in guayule is the stimulation of rubber biosynthesis by the exposure of the plants to low temperatures, similar to those existing in the fall and winter in the Chihuahuan Desert (Bonner, 1943;Downes and Tonnet, 1985;van Staden et al, 1986). Bonner (1943) demonstrated that the exposure of guayule plants to 27OC during the day and 7OC at night with an 8-h photoperiod for 4 months in a controlled-temperature greenhouse induced a 4-fold increase in rubber formation compared with plants grown at 27OC during the day and 27OC at night with an 8-h photoperiod.…”

“…There also was a severalfold increase in the incorporation of [14C]acetate and [14C]mevalonate into rubber in the stems of the cold-treated plants, which suggests that a faster rate of reactions in the polyisoprenoid pathway accounted for the increase in rubber biosynthesis. Rubber transferase activity in homogenates of the bark from lower stems of guayule plants exposed to the low fall and winter temperatures in the Chihuahuan Desert showed a 12-fold increase over the activity in plants during the summer months (Madhavan et al, 1988). The low temperatures may induce the expression of genes coding for the synthesis of enzymes involved in rubber biosynthesis in guayule plants (Bonner, 1975).…”

Isolation, Characterization, and Functional Analysis of a Novel cDNA Clone Encoding a Small Rubber Particle Protein from Hevea brasiliensis

“…Rubber transferase (cis-prenyltransferase) activity has been reported from the rubber particle-bound proteins of three rubber-producing plants, H. brasiliensis (17,29), Parthenium argentatum (23,30), and Ficus elastica (24). Although at least two rubber particle-associated proteins, a REF and a rubber transferase, have been suggested to be involved in rubber biosynthesis in H. brasiliensis (3,31,32), the detailed mechanism of rubber biosynthesis has not been investigated.…”