12 research outputs found
Uncovering mechanisms of rubber biosynthesis in Taraxacum koksaghyz - role of cis-prenyltransferase-like 1 protein
The Russian dandelion Taraxacum koksaghyz synthesizes considerable amounts of highâmolecularâweight rubber in its roots. The characterization of factors that participate in natural rubber biosynthesis is fundamental for the establishment of T. koksaghyz as a rubber crop. The cisâ1,4âisoprene polymers are stored in rubber particles. Located at the particle surface, the rubber transferase complex, member of the cisâprenyltransferase (cisPT) enzyme family, catalyzes the elongation of the rubber chains. An active rubber transferase heteromer requires a cisPT subunit (CPT) as well as a CPTâlike subunit (CPTL), of which T. koksaghyz has two homologous forms: TkCPTL1 and TkCPTL2, which potentially associate with the rubber transferase complex. Knockdown of TkCPTL1, which is predominantly expressed in latex, led to abolished poly(cisâ1,4âisoprene) synthesis but unaffected dolichol content, whereas levels of triterpenes and inulin were elevated in roots. Analyses of latex from these TkCPTL1âRNAi plants revealed particles that were similar to native rubber particles regarding their particle size, phospholipid composition, and presence of small rubber particle proteins (SRPPs). We found that the particles encapsulated triterpenes in a phospholipid shell stabilized by SRPPs. Conversely, downregulating the lowâexpressed TkCPTL2 showed no altered phenotype, suggesting its protein function is redundant in T. koksaghyz. MSâbased comparison of latex proteomes from TkCPTL1âRNAi plants and T. koksaghyz wildâtypes discovered putative factors that convert metabolites in biosynthetic pathways connected to isoprenoids or that synthesize components of the rubber particle shell