红砂(Reaumuria soongorica)黄酮类物质代谢及其抗氧化活性对UV-B辐射的响应

对荒漠植物红砂(Reaumuria soongorica)在UV-B辐射胁迫下不同时间内(0、2、4、6、8、10d)脂质过氧化、叶绿素和类胡萝卜素含量的变化以及黄酮类代谢途径关键酶活性、代谢产物及代谢产物的抗氧化活性进行了分析,探讨黄酮类代谢响应UV-B辐射胁迫的变化以及与脂质过氧化和光合色素系统的相关性。结果表明:随着UV-B辐射处理时间的延长,叶绿素含量有所降低;类胡萝卜素含量升高;膜脂过氧化程度(以丙二醛(MDA)含量表示)增加;黄酮类代谢途径关键酶黄烷酮3-羟化酶(F3H)活性呈现先增加后降低的趋势,但仍高于处理前水平,二氢黄酮醇4-还原酶(DFR)活性增强,代谢终产物总黄酮含量先降低后恢复至处理前水平,花色素苷(ANS)含量上升;DFR活性、黄酮类代谢产物ANS及总黄酮对DPPH清除率和对MDA形成的抑制率均与MDA以及光合色素系统之间存在显著或极显著的相关性。这表明次生物质黄酮类代谢途径在UV-B胁迫下发挥了抗氧化功能,提高红砂对在UV-B辐射下的自我保护能力。

Responses of the Flavonoid Pathway and Antioxidant Ability to UV-B Radiation Stress in Reaumuria soongorica

Reaumuria soongorica is a dwarf shrub mainly found in desert areas of North-west China, and can survive severe environmental stress. Due to the depletion of ozone layer, enhanced UV-B radiation is becoming one most important component of terrestrial radiation that plants are exposed to. This study aimed to assess the responses of the flavonoid pathway and its antioxidant activity to UV-B radiation treatments and its correlation to the lipid peroxide and photosynthetic pigments in R. soongorica leaves. For UV-B treatment, the plants were planted under enhanced UV-B radiation with an intensity of 0.3 mW·cm^-2 (20% higher than average natural UV-B radiation dose) at middy by hanging UV-B lamps above the plants. Contents of chlorophyll and carotenoid, levels of lipid peroxidation, activities of flavanone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR), accumulations of total flavonoids and anthocyanins (ANS) and the scavenging 1,1-Diphenyl-2-picrylhydrazyl radical 2,2 diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) ability and malondialdehyde (MDA) inhibition rate of total flavonoids under different UV-B radiation treatments were investigated. The correlations between key enzymes, products and antioxidant ability of flavonoids in the flavonoid pathway and the lipid peroxide and photosynthetic pigments were also analyzed. The results showed that: The chlorophyll contents decreased and carotenoid content significantly increased with the treatment time increased. The level of MDA increased. The contents of total flavonoids decreased within 4 days and then recovered to the same level as untreatmented. The contents of ANS, DFR activity and ability of scavenging DPPH increased under UV-B stress. The activities of F3H increased within 6 days and then decreased. The flavonoid products ANS, DFR activity and ability of scavenging DPPH and MDA inhibition had significant correlations with MDA level, as well as the photosynthetic pigments contents. Thus, we speculate that under enhanced UV-B radiation, the the flavonoid pathway played important role as antioxidant, and protected the R. soongorica from damaging by UV-B radiation stress.