Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase
Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase
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DOI：
10.1073/pnas.2436325100
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发表时间：
2003-11-25
影响因子：
11.1
通讯作者：
Croteau, RB
中科院分区：
文献类型：
--
作者：
Mahmoud, SS;Croteau, RB
（+）-胡薄荷酮是（-）-薄荷醇生物合成的中心中间体，薄荷醇是薄荷精油的最重要组分。取决于环境条件，该分支点代谢物可通过胡薄荷酮还原酶（PR）还原为（-）-薄荷酮，或通过薄荷呋喃合酶（MFS）氧化为（+）-薄荷呋喃。为了阐明胡薄荷酮代谢的调节，我们修改了在转化的薄荷植物中CaMV 35 S启动子控制下的MFS的表达。MFS的过表达和共抑制分别导致薄荷呋喃产量的增加或减少，表明MFS的控制主要存在于转录水平。显著地，在WT薄荷以及所有转化的植物中，（+）-胡薄荷酮通过PR的通量与薄荷呋喃的精油含量负相关，使得薄荷呋喃和胡薄荷酮一致地增加或减少。这些结果表明，薄荷呋喃本身可能会影响胡薄荷酮的还原。虽然（+）-薄荷呋喃没有抑制（+）-PR活性，但用薄荷呋喃喂茎选择性地降低未成熟叶片中的PR转录水平，从而解释还原酶活性降低和胡薄荷酮含量增加。这些数据表明，（+）胡薄荷酮的代谢命运是通过mfs的转录调控来控制的，而薄荷呋喃通过下调pr的转录和/或降低pr信息的稳定性来直接或间接地影响这一过程。降低薄荷呋喃和胡薄荷酮水平的能力在改善精油质量方面具有商业意义;然而，这种复杂调节的生理学原理目前尚不清楚。
(+)-Pulegone is a central intermediate in the biosynthesis of (-)-menthol, the most significant component of peppermint essential oil. Depending on environmental conditions, this branch point metabolite may be reduced to (-)-menthone en route to menthol, by pulegone reductase (PR), or oxidized to (+)-menthofuran, by menthofuran synthase (MFS). To elucidate regulation of pulegone metabolism, we modified the expression of mfs under control of the CaMV 35S promoter in transformed peppermint plants. Overexpression and cosuppression of mfs resulted in the respective increase or decrease in the production of menthofuran, indicating that the control of MFS resides primarily at the level of transcription. Significantly, in both WT peppermint as well as in all transformed plants, the flux of (+)-pulegone through PR correlated negatively with the essential oil content of menthofuran, such that menthofuran, and pulegone increased, or decreased, in concert. These results suggested that menthofuran itself might influence the reduction of pulegone. Although (+)-menthofuran did not inhibit (+)-PR activity, stem feeding with menthofuran selectively decreased pr transcript levels in immature leaves, thereby accounting for decreased reductase activity and increased pulegone content. These data demonstrate that the metabolic fate of (+)pulegone is controlled through transcriptional regulation of mfs and that menthofuran, either directly or indirectly, influences this process by down-regulating transcription from pr and/or decreasing pr message stability. The ability to reduce both menthofuran and pulegone levels is of commercial significance in improving essential oil quality; however, the physiological rationale for such complex regulation is presently unclear.