AUTHOR=Lakusta Adam M. , Kwon Moonhyuk , Kwon Eun-Joo G. , Stonebloom Solomon , Scheller Henrik V. , Ro Dae-Kyun 

TITLE=Molecular Studies of the Protein Complexes Involving Cis-Prenyltransferase in Guayule (Parthenium argentatum), an Alternative Rubber-Producing Plant

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00165

DOI=10.3389/fpls.2019.00165

ISSN=1664-462X

ABSTRACT=<p>Guayule (<italic>Parthenium argentatum</italic>) is a perennial shrub in the Asteraceae family and synthesizes a high quality, hypoallergenic <italic>cis</italic>-1,4-polyisoprene (or natural rubber; NR). Despite its potential to be an alternative NR supplier, the enzymes for <italic>cis</italic>-polyisoprene biosynthesis have not been comprehensively studied in guayule. Recently, implications of the protein complex involving <italic>cis</italic>-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 <italic>PaCPTs</italic> (<italic>PaCPT1-3</italic>) and one <italic>PaCBP</italic>, whose protein products organize PaCPT/PaCBP complexes. Co-expression of both <italic>PaCBP</italic> and each of the <italic>PaCPTs</italic> could complemented the dolichol (a short <italic>cis</italic>-polyisoprene)-deficient yeast, whereas the individual expressions could not. Microsomes from the <italic>PaCPT/PaCBP</italic>-expressing yeast efficiently incorporated <sup>14</sup>C-isopentenyl diphosphate into dehydrodolichyl diphosphates; however, NR with high molecular weight could not be synthesized in <italic>in vitro</italic> assays. Furthermore, co-immunoprecipitation and split-ubiquitin yeast 2-hybrid assays using PaCPTs and PaCBP confirmed the formation of protein complexes. Of the three <italic>PaCPT</italic>s, guayule transcriptomics analysis indicated that the <italic>PaCPT3</italic> 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.</p>