Molecular Studies of the Protein Complexes Involving -Prenyltransferase in Guayule (), an Alternative Rubber-Producing Plant

Guayule () is a perennial shrub in the Asteraceae family and synthesizes a high quality, hypoallergenic -1,4-polyisoprene (or natural rubber; NR). Despite its potential to be an alternative NR supplier, the enzymes for -polyisoprene biosynthesis have not been comprehensively studied in guayule. Recently, implications of the protein complex involving -prenyltransferases (CPTs) and CPT-Binding Proteins (CBPs) in NR biosynthesis were shown in lettuce and dandelion, but such protein complexes have yet to be examined in guayule. Here, we identified four guayule genes - three () and one , whose protein products organize PaCPT/PaCBP complexes. Co-expression of both and each of the could complemented the dolichol (a short -polyisoprene)-deficient yeast, whereas the individual expressions could not. Microsomes from the -expressing yeast efficiently incorporated C-isopentenyl diphosphate into dehydrodolichyl diphosphates; however, NR with high molecular weight could not be synthesized in assays. Furthermore, co-immunoprecipitation and split-ubiquitin yeast 2-hybrid assays using PaCPTs and PaCBP confirmed the formation of protein complexes. Of the three s, guayule transcriptomics analysis indicated that the is predominantly expressed in stem and induced by cold-stress, suggesting its involvement in NR biosynthesis. The comprehensive analyses of these PaCPTs and PaCBP here provide the foundational knowledge to generate a high NR-yielding guayule.