Irmisch Sandra, Krause Sandra T, Kunert Grit, Gershenzon Jonathan, Degenhardt Jörg, Köllner Tobias G
Institute of Pharmacy, Martin Luther University, Halle 06120, Germany.
BMC Plant Biol. 2012 Jun 8;12:84. doi: 10.1186/1471-2229-12-84.
The essential oil of chamomile, one of the oldest and agronomically most important medicinal plant species in Europe, has significant antiphlogistic, spasmolytic and antimicrobial activities. It is rich in chamazulene, a pharmaceutically active compound spontaneously formed during steam distillation from the sesquiterpene lactone matricine. Chamomile oil also contains sesquiterpene alcohols and hydrocarbons which are produced by the action of terpene synthases (TPS), the key enzymes in constructing terpene carbon skeletons.
Here, we present the identification and characterization of five TPS enzymes contributing to terpene biosynthesis in chamomile (Matricaria recutita). Four of these enzymes were exclusively expressed in above-ground organs and produced the common terpene hydrocarbons (-)-(E)-β-caryophyllene (MrTPS1), (+)-germacrene A (MrTPS3), (E)-β-ocimene (MrTPS4) and (-)-germacrene D (MrTPS5). A fifth TPS, the multiproduct enzyme MrTPS2, was mainly expressed in roots and formed several Asteraceae-specific tricyclic sesquiterpenes with (-)-α-isocomene being the major product. The TPS transcript accumulation patterns in different organs of chamomile were consistent with the abundance of the corresponding TPS products isolated from these organs suggesting that the spatial regulation of TPS gene expression qualitatively contribute to terpene composition.
The terpene synthases characterized in this study are involved in the organ-specific formation of essential oils in chamomile. While the products of MrTPS1, MrTPS2, MrTPS4 and MrTPS5 accumulate in the oils without further chemical alterations, (+)-germacrene A produced by MrTPS3 accumulates only in trace amounts, indicating that it is converted into another compound like matricine. Thus, MrTPS3, but also the other TPS genes, are good markers for further breeding of chamomile cultivars rich in pharmaceutically active essential oils.
洋甘菊是欧洲最古老且在农业上最重要的药用植物之一，其精油具有显著的抗炎、解痉和抗菌活性。它富含薁类化合物，这是一种在蒸汽蒸馏过程中由倍半萜内酯母菊天蓝烃自发形成的具有药理活性的化合物。洋甘菊油还含有倍半萜醇和碳氢化合物，这些物质是由萜类合酶（TPS）作用产生的，TPS是构建萜类碳骨架的关键酶。
在此，我们展示了对五种参与洋甘菊（母菊）萜类生物合成的TPS酶的鉴定和表征。其中四种酶仅在地上器官中表达，并产生常见的萜类碳氢化合物（-）-（E）-β-石竹烯（MrTPS1）、（+）-吉马烯A（MrTPS3）、（E）-β-罗勒烯（MrTPS4）和（-）-吉马烯D（MrTPS5）。第五种TPS，即多产物酶MrTPS2，主要在根部表达，并形成几种菊科特有的三环倍半萜，其中（-）-α-异伊索堇叶烯是主要产物。洋甘菊不同器官中TPS转录本的积累模式与从这些器官中分离出的相应TPS产物的丰度一致，这表明TPS基因表达的空间调控在质量上有助于萜类成分的形成。
本研究中表征的萜类合酶参与了洋甘菊精油的器官特异性形成。虽然MrTPS1、MrTPS2、MrTPS4和MrTPS5的产物在精油中积累而无需进一步的化学改变，但MrTPS3产生的（+）-吉马烯A仅微量积累，这表明它会转化为另一种化合物，如母菊天蓝烃。因此，MrTPS3以及其他TPS基因，是进一步培育富含具有药理活性精油的洋甘菊品种的良好标记。
