The Key Role of Phloroglucinol O-Methyltransferase in the Biosynthesis of Rosa chinensis Volatile 1,

The Key Role of Phloroglucinol O-Methyltransferase in the Biosynthesis of Rosa chinensis Volatile 1,

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The Key Role of Phloroglucinol O -Methyltransferase in the Biosynthesis of Rosa chinensis Volatile 1,3,5-Trimethoxybenzene 1 Shuiqin Wu, Naoharu Watanabe*, Satoru Mita, Hideo Dohra, Yoshihiro Ueda, Masaaki Shibuya, and Yutaka Ebizuka Department of Applied Biological Chemistry, Faculty of Agriculture (S.W., N.W.), and Institute for Genetic Research and Biotechnology (S.M., H.D.), Shizuoka University, Shizuoka 422–8529, Japan; Center for Environment, Health and Field Science, Chiba University, Kashiwa, Chiba 277–0882, Japan (Y.U.); and Department of Natural Product Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyoku, Tokyo 113–0033, Japan (M.S., Y.E.) 1,3,5-Trimethoxybenzene is a key component of the Chinese rose odor. This compound is synthesized in three successive methylation steps from phloroglucinol, the initial precursor. A novel, to our knowledge, phloroglucinol O -methyltransferase (POMT) characterized here methylates the ±rst step to produce the intermediate 3,5-dihydroxyanisole, while two previously described orcinol O -methyltransferases catalyze the subsequent steps. We isolated POMT from rose petals and determined partial amino acid sequences of the puri±ed enzyme. The full-length POMT cDNA was isolated and expressed in Escherichia coli . Both the native and recombinant POMT exhibited substrate speci±city for phloroglucinol. POMT was expressed speci±cally in ²oral organs, in accordance with its role as a key enzyme in the synthesis of rose ²oral scent compounds. Roses have been called the queen of ²owers and are one of the economically most important groups of ornamental plants (Krussmann, 1981). More than 150 rose species and 20,000 cultivars have been registered (Cairns, 2000), most of which belong to the lineage of Chinese roses. These lines originated around 1752, when Chinese roses were ±rst introduced to Europe and were bred for traits such as ²ower shape, recurrent ²owering, and scent (Wylie, 1954). However, most modern roses losttheirfragrancewhen breedingefforts focused on ²oral color and shape (Zuker et al., 1998). Studies on rose ²oral scent have concentrated on its chemical composition (Watanabe et al., 1998). Roses emit three main classes of compounds: phenolic derivatives, terpenoids, and fatty acid derivatives (Flament et al., 1993). However, little is known about enzymes and genes responsible for the biosynthesis of these substances. Only recently, the rose has attracted the attention of molecular biologists because of its commercial value (Channeliere et al., 2002; Guterman et al., 2002; Lavid et al., 2002; Shalit et al., 2003). Roses have a relatively small genome (Yokoya et al., 2000) and thus are regarded good model species for genetic studies of scent production. Rosa chinensis , the ancestor of modern roses (Rougetel, 1988), emits many scent compounds that are not present any more in most modern roses. In particular, 1,3,5-trimethoxybenzene (TMB) has been identi±ed as a key component of the speci±c Chinese rose odor (Yomogida, 1992). This volatile is an effective sedative and has been used as a cosmetic additive (Shoji et al., 2000).
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The Key Role of Phloroglucinol O-Methyltransferase in the Biosynthesis of Rosa chinensis Volatile 1,

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