Cultivation Base of State Key Laboratory for Ecological Restoration and Ecosystem Management of Jilin Province and Ministry of Science and Technology, College of Chinese Medicinal Materials, Jilin Agricultural University, 130118, Changchun, Jilin, PR China.
National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, 130118, Changchun, Jilin, PR China.
Phytochemistry. 2020 Sep;177:112434. doi: 10.1016/j.phytochem.2020.112434. Epub 2020 Jun 13.
Drought stress affects vegetative and reproductive growth processes and synthesis of secondary metabolites in plants. We assessed relevant indicators of vegetative and reproductive growth in Bupleurum chinense DC. during drought stress. Samples were collected on days 4, 8, 12, 20, and 24 of a drought treatment according to drought stress severity in order to elucidate potential effects on synthesis of flavonoids in leaves and saikosaponins in roots of B. chinense. The results showed that B. chinense can adapt to drought stress mainly by increasing concentrations of osmoregulatory substances (soluble protein and proline) and increasing activity of protective enzymes (superoxide dismutase and catalase), as observed on days 12 and 20 of the treatment. Secondary metabolite concentrations in B. chinense roots and leaves showed significant differences-drought stress increased saikosaponin concentrations in roots by 9.85% and 6.41% during vegetative and reproductive growth, respectively, on day 20, and saikosaponin concentrations in roots were higher during vegetative growth than during reproductive growth. In leaves, large amounts of antioxidants were consumed owing to drought stress, which decreased leaf rutin concentrations by 38.79% and 30.11% during vegetative and reproductive growth, respectively, as observed on day 20; overall, leaf rutin concentrations were lower during vegetative growth than during reproductive growth. Changes in soil water content are known to affect synthesis of secondary metabolites in medicinal plants by altering gene transcription, and affected genes may synergistically respond to soil water changes and alter concentrations of flavonoid in leaves and of saikosaponin in roots. The gene F3H down-regulates flavonoid production in leaves. Squalene epoxidase and β-amyrin synthase genes may be key genes regulating saikosaponin accumulation, and changes in their expression corresponded to accumulation of saikosaponins. Our results provide insights in B. chinense adaptation to drought stress through physiological changes and regulation of secondary metabolite production in different plant tissues.
干旱胁迫影响植物的营养生长和生殖生长过程以及次生代谢产物的合成。我们评估了柴胡在干旱胁迫下营养生长和生殖生长的相关指标。根据干旱胁迫的严重程度，在干旱处理的第 4、8、12、20 和 24 天采集样品，以阐明其对柴胡叶片中类黄酮和根中柴胡皂苷合成的潜在影响。结果表明，柴胡主要通过增加渗透调节物质（可溶性蛋白和脯氨酸）的浓度和增加保护酶（超氧化物歧化酶和过氧化氢酶）的活性来适应干旱胁迫，这在处理的第 12 和 20 天观察到。柴胡根和叶中的次生代谢产物浓度存在显著差异-在营养生长和生殖生长过程中，干旱胁迫分别使根中柴胡皂苷的浓度增加了 9.85%和 6.41%，在第 20 天，根中的柴胡皂苷浓度在营养生长过程中高于生殖生长过程。在叶片中，由于干旱胁迫，大量抗氧化剂被消耗，导致叶片芦丁的浓度分别在营养生长和生殖生长过程中降低了 38.79%和 30.11%，在第 20 天观察到；总体而言，叶片芦丁的浓度在营养生长过程中低于生殖生长过程。土壤水分的变化被认为通过改变基因转录来影响药用植物次生代谢产物的合成，受影响的基因可能协同响应土壤水分的变化并改变叶片中类黄酮和根中柴胡皂苷的浓度。F3H 基因下调叶片中类黄酮的产生。鲨烯环氧化酶和β-香树脂醇合酶基因可能是调节柴胡皂苷积累的关键基因，其表达的变化与柴胡皂苷的积累相对应。我们的研究结果为柴胡通过不同植物组织中次生代谢产物的生理变化和调节来适应干旱胁迫提供了新的见解。
