UV-B胁迫下Ca 2+对颠茄生理特性与次生代谢产物的调控研究

有害中波紫外线(Ultraviolet B, UV-B; 280~320 nm)辐射影响植物的生长和发育, Ca ²⁺是植物生长发育所必须的大量元素之一, 外源Ca ²⁺不但可以提高植物抗胁迫能力, 还对次生代谢具有调控作用。以颠茄(Atropa belladonna L.)实生苗为材料, 在UV-B辐射(10 μW cm ^-2)背景下, 研究不同浓度外源Ca ²⁺、不同处理时间对颠茄生理特性、氮代谢、次生代谢产物含量以及托品烷类生物碱代谢途径中3个关键酶基因表达量的影响。结果表明, 随着UV-B辐射时间的延长(4 ~12 d), 对颠茄的光合作用、氮代谢以及生物碱的积累产生抑制作用, 加剧了膜脂氧化程度; 经外源Ca ²⁺处理, 叶片初始荧光(F_o)、丙二醛(malondialdehyde, MDA)含量呈下降趋势, 叶片最大光化学效率(F_v/F_m)、光合色素(总叶绿素、类胡萝卜素)含量、抗氧化酶(SOD、POD、CAT)活性均呈上升趋势, 说明Ca ²⁺有利于缓解UV-B辐射的抑制, 加强对UV-B胁迫的抗性; 在Ca ²⁺处理下, 叶片中硝态氮含量显著降低, 游离氨基酸、可溶性蛋白含量和氮代谢关键酶(NR、GS、GDH)的活性显著提高, 叶片中莨菪碱含量和东莨菪碱含量显著提高; qRT-PCR分析显示, 在外源Ca ²⁺的诱导下, 托品烷类生物碱合成途径中3个关键酶基因(PMT、TR I、H6H)表达量均有不同程度上调趋势。本研究结果可为田间种植提供理论参考。

Effect of Exogenous Ca 2+ on Physiological Characteristics and Secondary Metabolites accumulation of Atropa belladonna L. Seedlings under UV-B Stress

Ultraviolet B (UV-B) radiation does harm to plant, for which growth and development. Ca ²⁺is one of the most necessary elements. Exogenous Ca ²⁺ can enhance plant abilities to resist stress and regulate secondary metabolism. In this research, we used Atropa belladonna L. seedlings to investigate the effects of different concentrations of exogenous Ca ²⁺ and different treatment days on the physiological characteristics, nitrogen metabolism, secondary metabolites content and relative genes expression levels of three key enzymes in secondary metabolism under the background of UV-B radiation. The UV-B radiation not only caused inhibitory effect on the Atropa belladonna L. photosynthesis, nitrogen metabolism, alkaloid content, but also increased peroxidation of membrane lipid. The F_o, MDA content gradually decreased, but the F_v/F_m, photosynthetic pigment content, antioxidant enzyme activity gradually increased under Ca ²⁺ treatment, showing that Ca ²⁺ is propitious to relieve inhibitory effect on photosynthesis and enhance resistance to UV-B stress. Moreover, Ca ²⁺ reduced the content of nitrate nitrogen significantly, promoted the contents of free amino acids, soluble proteins, atropine alkaloids, and raised the activities of key enzymes in nitrogen metabolism. Using real-time fluorescence quantitative PCR, we found that exogenous Ca ²⁺ increased the relative gene expression levels of three key enzymes in secondary metabolism in different degrees. This research could provide a theoretical references for plantation in the field.