Rehmannia glutinosa, one of the most widely used herbal medicines in the Orient, is rich in biologically active iridoids. Despite their medicinal importance, no molecular information about the iridoid biosynthesis in this plant is presently available. To explore the transcriptome of R. glutinosa and investigate genes involved in iridoid biosynthesis, we used massively parallel pyrosequencing on the 454 GS FLX Titanium platform to generate a substantial EST dataset. Based on sequence similarity searches against the public sequence databases, the sequences were first annotated and then subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) based analysis. Bioinformatic analysis indicated that the 454 assembly contained a set of genes putatively involved in iridoid biosynthesis. Significantly, homologues of the secoiridoid pathway genes that were only identified in terpenoid indole alkaloid producing plants were also identified, whose presence implied that route II iridoids and route I iridoids share common enzyme steps in the early stage of biosynthesis. The gene expression patterns of four prenyltransferase transcripts were analyzed using qRT-PCR, which shed light on their putative functions in tissues of R. glutinosa. The data explored in this study will provide valuable information for further studies concerning iridoid biosynthesis.
Cai, Q.Y.; Chen, X.S.; Zhan, X.L.; Yao, Z.X. Protective effects of catalpol on oligodendrocyte death and myelin breakdown in a rat model of chronic cerebral hypoperfusion. Neurosci. Lett 2011, 497, 22–26.
Jensen, S.R. Plant iridoids, Their Biosynthesis and Distribution in Angiosperms. In Ecological Chemistry and Biochemistry of Plant Terpenoids; Harborne, J.B., Tomas-Barberan, F.A., Eds.; Clarendon Press: Oxford, UK, 1991; pp. 133–158.
Veau, B.; Courtois, M.; Oudin, A.; Chenieux, J.C.; Rideau, M.; Clastre, M. Cloning and expression of cDNAs encoding two enzymes of the MEP pathway in Catharanthus roseus. Biochem. Biophys. Acta 2000, 1517, 159–163.
Burlat, V.; Oudin, A.; Courtois, M.; Rideau, M.; St-Pierre, B. Co-expression of three MEP pathway genes and geraniol 10-hydroxylase in internal phloem parenchyma of Catharanthus roseus implicates multicellular translocation of intermediates during the biosynthesis of monoterpene indole alkaloids and isoprenoid-derived primary metabolites. Plant J 2004, 38, 131–141.
Wang, Z.; Fang, B.; Chen, J.; Zhang, X.; Luo, Z.; Huang, L.; Chen, X.; Li, Y. De novo assembly and characterization of root transcriptome using Illumina paired-end sequencing and development of cSSR markers in sweet potato (Ipomoea batatas). BMC Genomics 2010, 11, 726–739.
Wu, S.; Schalk, M.; Clark, A.; Miles, R.B.; Coates, R.; Chappell, J. Redirection of cytosolic or plastidic isoprenoid precursors elevates terpene production in plants. Nature Biotech 2006, 24, 1441–1447.
Contin, A.; van der Heijden, R.; Lefeber, A.W.; Verpoorte, R. The iridoid glucoside secologanin is derived from the novel triose phosphate/pyruvate pathway in a Catharanthus roseus cell culture. FEBS Lett 1998, 434, 413–416.
Yamazaki, Y.; Kitajima, M.; Arita, M.; Takayama, H.; Sudo, H.; Yamazaki, M.; Aimi, N.; Saito, K. Biosynthesis of camptothecin. In silico and in vivo tracer study from [1–13C]glucose. Plant Physiol 2004, 134, 161–170.
Courdavault, V.; Thiersault, M.; Courtois, M.; Gantet, P.; Oudin, A.; Doireau, P.; St-Pierre, B.; Giglioli-Guivarc’h, N. CaaX-prenyltransferases are essential for expression of genes involved in the early stages of monoterpenoid biosynthetic pathway in Catharanthus roseus cells. Plant Mol. Biol 2005, 57, 855–870.
Welsch, R.; Wüst, F.; B？r, C.; Al-Babili, S.; Beyer, P. A third phytoene synthase is devoted to abiotic stress-induced abscisic acid formation in rice and defines functional diversification of phytoene synthase genes. Plant Physiol 2008, 147, 367–380.
Keller, Y.; Bouvier, F.; d’Harlingue, A.; Camara, B. Metabolic compartmentation of plastid prenyllipid biosynthesis-evidence for the involvement of a multifunctional geranylgeranyl reductase. Eur. J. Biochem 1998, 251, 413–417.
Tanaka, R.; Oster, U.; Kruse, E.; Rudiger, W.; Grimm, B. Reduced activity of geranylgeranyl reductase leads to loss of chlorophyll and tocopherol and to partially geranylgeranylated chlorophyll in transgenic tobacco plants expressing antisense RNA for geranylgeranyl reductase. Plant Physiol 1999, 120, 695–704.
Burke, C.C.; Croteau, R. Interactions with the small subunit of geranyl diphosphate synthase modifies the chain length specificity of geranylgeranyl diphosphate synthase to produce geranyl diphosphate. J. Biol. Chem 2002, 277, 3141–3149.
Vandermoten, S.; Haubruge, E.; Cusson, M. New insights into short-chain prenyltransferases: structural features, evolutionary history and potential for selective inhibition. Cell. Mol. Life Sci 2009, 66, 3685–3695.