Guangxi Key Laboratory of Medicinal Resource Protection and Genetic Improvement, Guangxi Botanical Garden of Medicinal Plants, Nanning, 530023, China; Guangxi Engineering Research Centre of TCM Intelligent Creation, Guangxi Botanical Garden of Medicinal Plants, Nanning, 530023, China.
Guangxi Key Laboratory of Medicinal Resource Protection and Genetic Improvement, Guangxi Botanical Garden of Medicinal Plants, Nanning, 530023, China; Guangxi Engineering Research Centre of TCM Intelligent Creation, Guangxi Botanical Garden of Medicinal Plants, Nanning, 530023, China.
Plant Physiol Biochem. 2021 Jul;164:82-91. doi: 10.1016/j.plaphy.2021.04.016. Epub 2021 May 5.
Nitrogen (N) form affects secondary metabolites of medicinal plants, but the physiological and molecular mechanisms remain largely unknown. To fully understand the response of andrographolide biosynthesis to different N forms in Andrographis paniculata, the plants were fed with nutritional solution containing sole N source of nitrate (NO), ammonium (NH), urea or glycine (Gly), and the growth, carbon (C) and N metabolisms and andrographolide biosynthesis were analyzed. We found that plants grown in urea and Gly performed greater photosynthetic rate and photosynthetic N use efficiency (PNUE) than those grown in NO and NH. Organic N sources reduced the activities of enzymes involving in C and N metabolisms such as glutamine synthase (GS), glutamate synthase (GOGAT) and NADH-dependent glutamate dehydrogenase (NADH-GDH), invertase (INV), isocitrate dehydrogenase (ICDH) and glycolate oxidase (GO), resulting in reduced depletion of carbohydrates and increased starch accumulation. However, they enhanced andrographolide content by up-regulating the key genes in its biosynthetic pathway including HMGR, DXS, GGPS and ApCPS. Besides, NH decreased leaf SPAD value, contents of soluble protein and amino acids and GO activity, but increased photosynthetic rate and contents of soluble sugar and starch in comparison to NO. Andrographolide biosynthesis was also up-regulated. The results revealed that increasing accumulation of carbohydrates, especially starch, was beneficial to the biosynthesis of andrographolide; organic N sources decreased carbohydrate depletion by reducing N metabolism, and promoted plant growth and andrographolide biosynthesis synergistically.
氮（N）形态会影响药用植物的次生代谢物，但生理和分子机制在很大程度上仍不清楚。为了全面了解穿心莲内酯生物合成对穿心莲不同 N 形态的响应，本研究用含有硝酸盐（NO）、铵（NH）、尿素或甘氨酸（Gly）单一 N 源的营养液来喂养植物，并分析了植物的生长、碳（C）和 N 代谢以及穿心莲内酯生物合成。结果发现，与在 NO 和 NH 中生长的植物相比，在尿素和 Gly 中生长的植物具有更高的光合速率和光合 N 利用效率（PNUE）。有机 N 源降低了参与 C 和 N 代谢的酶的活性，如谷氨酰胺合成酶（GS）、谷氨酸合酶（GOGAT）和 NADH 依赖的谷氨酸脱氢酶（NADH-GDH）、转化酶（INV）、异柠檬酸脱氢酶（ICDH）和乙醛酸氧化酶（GO），导致碳水化合物的消耗减少和淀粉积累增加。然而，它们通过上调其生物合成途径中的关键基因，如 HMGR、DXS、GGPS 和 ApCPS，来提高穿心莲内酯的含量。此外，与 NO 相比，NH 降低了叶片 SPAD 值、可溶性蛋白和氨基酸含量以及 GO 活性，但提高了光合速率、可溶性糖和淀粉含量。同时，穿心莲内酯的生物合成也被上调。研究结果表明，增加碳水化合物，尤其是淀粉的积累，有利于穿心莲内酯的生物合成；有机 N 源通过降低 N 代谢减少碳水化合物的消耗，并协同促进植物生长和穿心莲内酯的生物合成。
