Department of Biology and Biotechnology, Worcester Polytechnic Institute, WPI, Worcester, MA 01609, USA.
Molecules. 2010 Mar 30;15(4):2302-18. doi: 10.3390/molecules15042302.
The biosynthesis of the valuable sesquiterpene anti-malarial, artemisinin, is known to respond to exogenous sugar concentrations. Here young Artemisia annua L. seedlings (strain YU) were used to measure the transcripts of six key genes in artemisinin biosynthesis in response to growth on sucrose, glucose, or fructose. The measured genes are: from the cytosolic arm of terpene biosynthesis, 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), farnesyl disphosphate (FPS); from the plastid arm of terpene biosynthesis, 1-deoxyxylulose-5-phosphate synthase (DXS), 1-deoxyxylulouse 5-phosphate reductoisomerase (DXR); from the dedicated artemisinin pathway amorpha-4,11-diene synthase (ADS), and the P450, CYP71AV1 (CYP). Changes in intracellular concentrations of artemisinin (AN) and its precursors, dihydroartemisinic acid (DHAA), artemisinic acid (AA), and arteannuin B (AB) were also measured in response to these three sugars. FPS, DXS, DXR, ADS and CYP transcript levels increased after growth in glucose, but not fructose. However, the kinetics of these transcripts over 14 days was very different. AN levels were significantly increased in glucose-fed seedlings, while levels in fructose-fed seedlings were inhibited; in both conditions this response was only observed for 2 days after which AN was undetectable until day 14. In contrast to AN, on day 1 AB levels doubled in seedlings grown in fructose compared to those grown in glucose. Results showed that transcript level was often negatively correlated with the observed metabolite concentrations. When seedlings were gown in increasing levels of AN, some evidence of a feedback mechanism emerged, but mainly in the inhibition of AA production. Together these results show the complex interplay of exogenous sugars on the biosynthesis of artemisinin in young A. annua seedlings.
青蒿素是一种具有重要价值的倍半萜抗疟药物，其生物合成被认为对外源糖浓度有响应。本研究以青蒿（YU 株系）幼苗为材料，测量了在蔗糖、葡萄糖或果糖生长条件下，青蒿素生物合成中 6 个关键基因的转录水平。所测基因包括：细胞质萜类生物合成途径中的 3-羟基-3-甲基戊二酰辅酶 A 还原酶（HMGR）、法呢基二磷酸（FPS）；质体萜类生物合成途径中的 1-脱氧木酮糖-5-磷酸合酶（DXS）、1-脱氧木酮糖-5-磷酸还原异构酶（DXR）；专门的青蒿素途径中的 4,11-二烯合酶（ADS）和 P450，CYP71AV1（CYP）。还测量了青蒿素（AN）及其前体二氢青蒿酸（DHAA）、青蒿酸（AA）和青蒿素 B（AB）在细胞内的浓度变化，以响应这三种糖。葡萄糖生长后，FPS、DXS、DXR、ADS 和 CYP 的转录水平增加，但果糖生长后没有增加。然而，这些转录物在 14 天内的动力学非常不同。葡萄糖喂养的幼苗中 AN 水平显著增加，而果糖喂养的幼苗中 AN 水平受到抑制；在这两种情况下，这种反应仅在 2 天后观察到，此后 AN 直到第 14 天都无法检测到。与 AN 相反，在以果糖生长的幼苗中，AB 水平在第 1 天是葡萄糖生长幼苗的两倍。结果表明，转录水平通常与观察到的代谢物浓度呈负相关。当幼苗生长在不断增加的 AN 水平时，出现了一些反馈机制的证据，但主要是 AA 产量的抑制。这些结果表明，外源糖对青蒿幼苗中青蒿素生物合成的复杂相互作用。
