Biochemical regulation of rubber biosynthesis in guayule (Parthenium argentatum Gray)

Natural rubber is an irreplaceable raw material vital to industry, transportation, medicine and defense. It is largely produced from clonal plantations of Hevea brasiliensis in southeastern Asia. Temperate-zone rubber-producing crops are greatly desired to increase biodiversity, protect supplies, and provide a safe natural-rubber alternative for the large numbers of people suffering from Type I latex allergy to proteins in latex products. Parthenium argentatum (guayule) is currently under development in the United States as a suitable source of hypoallergenic latex. Improved P. argentatum lines are still desired with higher latex yields, improved agronomic characteristics, and broader growth range. Understanding the biochemical regulation of rubber yield (principally rate of synthesis) and quality (principally molecular weight distribution) in P. argentatum is an essential preliminary to the identification and manipulation of key regulatory steps. In this paper, the biochemical regulation of rubber biosynthesis in P. argentatum will be discussed and unique features highlighted. We find that the P. argentatum rubber transferase has kinetic features, such as high KmIPP, similar to other rubber producing species. However, P. argentatum also has some unique rubber transferase features, including very low KmFPP and negative cooperativity for C15 farnesyl pyrophosphate (FPP), which affect the way guayule regulates rubber biosynthesis.