(E)-β-ocimene and myrcene synthase genes of floral scent biosynthesis in snapdragon:: Function and expression of three terpene synthase genes of a new terpene synthase subfamily
(E)-β-ocimene and myrcene synthase genes of floral scent biosynthesis in snapdragon:: Function and expression of three terpene synthase genes of a new terpene synthase subfamily
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DOI：
10.1105/tpc.011015
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发表时间：
2003-05-01
期刊：
影响因子：
11.6
通讯作者：
Bohlmann, J
中科院分区：
文献类型：
--
作者：
Dudareva, N;Martin, D;Bohlmann, J
金鱼草的花除了主要的苯丙素类花香成分苯甲酸甲酯外，还散发出两种单萜烯烃，月桂烯和（E）-β-罗勒烯，它们来自于香叶基二磷酸。这些单萜的排放是受发育调节的，并遵循昼夜节律控制的生物钟。使用功能基因组学方法，我们已经分离和表征了三个密切相关的cDNA从金鱼草花瓣特异性库，编码两个月桂烯脱氢酶（ama 1 e20和ama 0 c15）和（E）-β-罗勒烯合酶（ama 0a 23）。虽然这两个月桂烯脱氢酶几乎相同（98%），除了N-末端13个氨基酸，并具有催化活性，产生一个单一的单萜产品，月桂烯，只有ama 0 c15是在花中高水平表达，并有助于花月桂烯排放。（E）-β-罗勒烯合酶与金鱼草月桂烯脱氢酶高度相似（92%氨基酸同一性），并且主要产生（E）-β-罗勒烯（总单萜烯烃产物的97%）以及少量的（Z）-β-罗勒烯和月桂烯。这些新分离的金鱼草单萜脱氢酶与拟南芥AtTPS 14（At 1g 61680）一起定义了一个新的萜合酶（TPS）家族亚家族，命名为Tps-g组。这个新的Tps-g组的成员缺乏RRX 8 W基序，这是Tps-d和Tps-b单萜脱氢酶的特征，表明Tps-g单萜合酶产物形成的反应机制不通过香叶基二磷酸到3S-芳樟基二磷酸的RR依赖性异构化进行，如先前对于柠檬烯环化酶所示。金鱼草花中这些单萜合酶基因的组织特异性、发育和节律性表达的分析揭示了类苯丙素和类异戊二烯气味产生的协调调节。
Snapdragon flowers emit two monoterpene olefins, myrcene and (E)-beta-ocimene, derived from geranyl diphosphate, in addition to a major phenylpropanoid floral scent component, methylbenzoate. Emission of these monoterpenes is regulated developmentally and follows diurnal rhythms controlled by a circadian clock. Using a functional genomics approach, we have isolated and characterized three closely related cDNAs from a snapdragon petal-specific library that encode two myrcene synthases (ama1e20 and ama0c15) and an (E)-beta-ocimene synthase (ama0a23). Although the two myrcene synthases are almost identical (98%), except for the N-terminal 13 amino acids, and are catalytically active, yielding a single monoterpene product, myrcene, only ama0c15 is expressed at a high level in flowers and contributes to floral myrcene emission. (E)-beta-Ocimene synthase is highly similar to snapdragon myrcene synthases (92% amino acid identity) and produces predominantly (E)-beta-ocimene (97% of total monoterpene olefin product) with small amounts of (Z)-beta-ocimene and myrcene. These newly isolated snapdragon monoterpene synthases, together with Arabidopsis AtTPS14 (At1g61680), define a new subfamily of the terpene synthase (TPS) family designated the Tps-g group. Members of this new Tps-g group lack the RRX8W motif, which is a characteristic feature of the Tps-d and Tps-b monoterpene synthases, suggesting that the reaction mechanism of Tps-g monoterpene synthase product formation does not proceed via an RR-dependent isomerization of geranyl diphosphate to 3S-linalyl diphosphate, as shown previously for limonene cyclase. Analyses of tissue-specific, developmental, and rhythmic expression of these monoterpene synthase genes in snapdragon flowers revealed coordinated regulation of phenylpropanoid and isoprenoid scent production.