城市臭氧污染对月季花瓣花青素合成的影响机制

With the accelaration of the urbanization and industrialization, increased ground-level ozone (O3) pollution has caused significant injuries to many plants. Anthocyanins represent the major red, purple, violet and blue pigments in many flowers. They attract pollinators and seed dispersers and defend plants against abiotic and biotic stresses. Considerable researches has been conducted on O3 effects on photosynthetic physiology and antioxidant systems, only a few studies have been made on O3 effects on metabolism and its molecular basis. It still remains unknown how urban O3 pollution affect anthocyanin biosynthesis in the petals, induce the flower color changes. To assess O3 effect on anthocyanin biosynthesis and explore possible underlying mechanisms, three major cultivars of Rosa hybrida for urban greening will be exposed to in site O3, charcoal-filtered air or elevated O3 at Beijing Urban Ecosystem Research Station in Beijing. This research will focuse on (1) identifying the content and component changes of anthocyanin, flavonoids, and proanthocyanidins in petals to O3 among the tested R.hybrida cultivars; (2) clarifying the possible physiological and biochemical aspects on differential responses to O3 among the cultivars in terms of ultramicrostructure of petals, stomatal uptake, endogenous plant hormones and antioxidant capacity; (3) clarifying the possible molecular basis on differential responses to O3 among the cultivars in terms of anthocynin biosysthesis related transcription factors RhMYBs and structure genes expressions; (4) deriving the relationship between stomatal O3 flux and athocynin biosysthesis with the stomatal conductance model, as well as analysing the relationships between physiological , biochemical, molecular aspects and athocynin biosysthesis. The objectives of the research will be to provide (1) materials and theoretical basis for revealing the mechanisms underlying the O3 effects on plant physiplogy; (2) data supporting for prevent and mitigate the negative effects of O3 pollution.

随着城市化与工业化，臭氧(O3)污染对很多植物造成明显的胁迫伤害。花青素是花瓣的主要呈色物质，具有抗氧化等功能，对植物的生长繁殖及对环境的适应有重要意义。但目前有关O3污染对花青素合成的影响及作用机理的研究还不够深入。本项目拟以北京市三个月季主栽品种为研究对象，采用定点取样、开顶式气室模拟城市O3浓度升高实验和室内分析测定相结合的方法，分析不同O3浓度下月季花瓣花青苷、类黄酮苷和原花青素的种类和含量，推定花青素合成途径的变化；明确内源激素和抗氧化指标的变化，揭示花青素合成与抗O3胁迫相关信号之间的关系；并结合花青素合成的转录因子(RhMYBs)和结构基因表达的差异，探讨O3污染诱导花瓣花青素合成基因的变化，揭示O3污染对花瓣花青素合成的影响机制；同时，建立气孔O3吸收通量与花青素含量的响应关系，评估与预测未来O3浓度升高对月季花色的潜在影响，为指导预防和减轻O3污染带来的负效应提供参考。

随着城市化与工业化，臭氧污染已对很多植物造成明显的胁迫伤害。月季是世界上重要观赏植物，也是城市绿化的重要组成部分。花青素是花瓣的主要呈色物质，具有抗氧化等功能，对植物生长有重要意义。但目前有关O3污染对花青素合成的影响及作用机理的研究还不够深入。本研究利用开顶式气室进行O3浓度升高野外模拟试验，结合室内分析测定，探讨近地层O3浓度升高对月季品种生长、生理、超微结构的影响，着重讨论了MYB转录因子在月季O3响应中的作用。整株水平上，月季品种曼海姆宫殿叶片均出现严重可见伤害症状，冰山少数叶片出现轻微的伤害症状，绿野和光谱叶片没有出现。同时，O3处理下，曼海姆宫殿和冰山花朵数和花径均显著降低，表明曼海姆宫殿为O3敏感型月季品种。生理水平上，O3浓度升高显著降低曼海姆宫殿叶片光合色素含量，羧化效率与电子传递效率受到抑制等非气孔因素导致叶片净光合速率显著降低，水分利用效率也显著降低。此外，O3浓度升高显著增加曼海姆宫殿花瓣花青素含量。超微结构上，O3浓度升高下，曼海姆宫殿成熟叶的气孔开度明显降低，叶片表皮蜡质明显增加；花瓣表面的沟回结构呈现一定程度的拉直，凹陷孔变大，蜡质明显增多。分子水平上，一方面，O3作为信号，通过调控转录因子MYB10的表达，激活花青素合成途径关键基因的表达，进而显著提高了曼海姆宫殿花瓣花青素的含量；另一方面，随着O3浓度升高，转录因子MYB17、MYB11、MYB15、DREB1B基因，以及ABA合成相关基因的表达显著上调，说明MYB转录因子在调控月季O3响应中发挥重要作用。此外，曼海姆宫殿吸收O3速率的日变化呈单峰曲线，夏季吸收O3速率高于秋季；吸收O3的时间变化规律取决于大气O3浓度和冠层对O3的导度。上述研究结果，为观赏植物重要经济性状分子生物学研究和分子育种提供参考，也可为指导预防和减轻O3污染带来的负效应提供参考。