Volatile components of tea and china roses and analysis of genetic resources by their biosynthetic genes

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(1)The volatile components from the flowers of 64 species and 239 cultivars including Chinese taxon were analysed by using GC-MS in the head-space GC analysis. Rosa chinensis var. spontanea, native to south-western China, emitted the greatest amount of 1,3,5-trimethoxybenzene as a key component of Chinese rose odor. Many of tea and china roses had genealogical relationship to ancestral species, R.chinensis var. spontanea and R.gigantea, through 1,3,5-trimethoxybenzene(TMB) and 1,3-dimethoxy-5-methylbenzene(DMMB) as the key components. However, among Chinese roses, there were some cultivars without these key components and it remains to be uncertain about the origin of those cultivars.(2)Among analysed ancient Chinese roses, we found that there were some cultivars emitted composition of volatile components different from existing Chinese roses. These are cultivars emitted well-balanced of TMB and DMMB, large quantity of TMB or DMMB and large quantity of dihydro-β-ionone. These cultivars will be valuable gene resources to breed new type fragrant roses.(3)Three O-methyltransferases were isolated from flower petals of Rosa chinensis var. spontanea and assayed to determine their substrate preferences. One of them workes well with 3,5-dihydroxyanisole, a putative precursor of TMB.(4)Phloroglucinol O-methyltransferase(POMT), which methylates the first step to produce the intermediate 3,5-dihydroxyanisole, was isolated from flower petals of R.chinensis var. spontanea and purified. The full-length POMT cDNA was isolated and expressed in Escherichia coli. POMT was expressed specifically in floral organs in accordance with its role as a key enzyme in the synthesis of rose floral scent compounds.