School of Life Sciences and State Key Laboratory for Agrobiotechnology, The Chinese University of Hong Kong, HKSAR, China.
Planta Med. 2011 Jul;77(10):1048-53. doi: 10.1055/s-0030-1250744. Epub 2011 Jan 25.
Considerable difference in artemisinin and its direct precursors, artemisinic acid and dihydroartemisinic acid, was detected between two chemotypes within the species Artemisia annua (A. annua). These two chemotypes showed differential metabolic response to methyl jasmonate (MeJA) elicitation. Exogenous application of MeJA resulted in an accumulation of dihydroartemisinic acid and artemisinin in Type I plants. In Type II plants, however, artemisinic acid and artemisinin level decreased dramatically under MeJA elicitation. Squalene and other sesquiterpenes, (e.g., caryophyllene, germacrene D), were stimulated by MeJA in both chemotypes. The effect of MeJA elicitation was also studied at the transcription level. Real time RT-PCR analysis showed a coordinated activation of most artemisinin pathway genes by MeJA in Type I plants. The lack of change in cytochrome P450 reductase (CPR) transcript in Type I plants indicates that the rate-limiting enzymes in artemisinin biosynthesis have yet to be identified. Other chemotype-specific electron donor proteins likely exist in A. annua to meet the demand for P450-mediated reactions in MeJA-mediated cellular processes. In Type II plants, mRNA expression patterns of most pathway genes were consistent with the reduced artemisinin level. Intriguingly, the mRNA transcript of aldehyde dehydrogenase1 (ADHL1), an enzyme which catalyzes the oxidation of artemisinic and dihydroartemisinic aldehydes, was upregulated by MeJA. The differential metabolic response to MeJA suggests a chemotype-dependent metabolic flux control towards artemisinin and sterol production in the species A. annua.
在青蒿（Artemisia annua）种内的两个化学型之间，检测到青蒿素及其直接前体青蒿酸和二氢青蒿酸存在相当大的差异。这两种化学型对茉莉酸甲酯（MeJA）激发表现出不同的代谢反应。MeJA 的外源应用导致 I 型植物中二氢青蒿酸和青蒿素的积累。然而，在 II 型植物中，MeJA 激发下青蒿酸和青蒿素的水平显著下降。角鲨烯和其他倍半萜烯（例如，石竹烯、大根香叶烯 D）在两种化学型中均被 MeJA 刺激。还在转录水平上研究了 MeJA 激发的效果。实时 RT-PCR 分析表明，I 型植物中大多数青蒿素途径基因被 MeJA 协调激活。I 型植物细胞色素 P450 还原酶（CPR）转录物没有变化表明青蒿素生物合成的限速酶尚未确定。其他化学型特异性电子供体蛋白可能存在于青蒿中，以满足 P450 介导的反应在 MeJA 介导的细胞过程中的需求。在 II 型植物中，大多数途径基因的 mRNA 表达模式与青蒿素水平降低一致。有趣的是，醛脱氢酶 1（ADHL1）的 mRNA 转录物，一种催化青蒿酸和二氢青蒿酸醛氧化的酶，被 MeJA 上调。对 MeJA 的不同代谢反应表明，青蒿种内的代谢通量控制依赖于化学型，朝向青蒿素和固醇的生产。
