Uncovering metabolic regulatory mechanisms connected to rubber biosynthesis by the down-regulation of CPTL1 in Taraxacum koksaghyz

ABSTRACT: The Russian dandelion Taraxacum koksaghyz synthesizes considerable amounts of high molecular weight rubber in its roots. The cis-1,4-isoprene polymers are stored as rubber particle in the latex, the cytosol of specialized cells, called laticifers. The rubber transferase complex localizes at the particle surface and catalyzes the elongation of the cis-1,4-isoprene chains. The heteromeric complex is composed of an NgBR-like protein and a cis-prenyltransferase. In T. koksaghyz two NgBR homologous proteins, TkCPTL1 and TkCPTL2 were identified. Spatial expression analysis showed that TkCPTL1 is predominantly expressed at a high rate in latex, whereas TkCPTL2 exhibits low mRNA levels in all tissues. We investigated the functions of TkCPTL1&2 in two RNAi approaches. The down-regulation of TkCPTL2 showed no altered phenotype indicating a redundant function of the protein in dandelion. Knockdown of TkCPTL1 led to abolished poly(cis-1,4-isoprene) synthesis indicating that TkCPTL1 is essentially contributing to the formation of the rubber polymer. Simultaneously, levels of triterpenes and inulin in roots were significantly elevated. Analyses of latex from TkCPTL1-RNAi plants yielded a newly appearing latex fraction still containing particles, which seemed to be unaffected in structure compared to native rubber particles. Particle size, phospholipid composition and presence of small rubber particle proteins were determined for this purpose. We could show that the particles encapsulate triterpenes in a phospholipid shell that is stabilized by SRPPs. MS-based comparison of latex proteomes from TkCPTL1-RNAi plants and T. koksaghyz wildtypes enabled evidences for regulation mechanisms in several metabolic pathways associated to rubber biosynthesis.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Taraxacum Sp.

TISSUE(S): Latex

SUBMITTER: Ines Lassowskat  

LAB HEAD: Iris Finkemeier

PROVIDER: PXD010953 | Pride | 2022-03-02

REPOSITORIES: Pride