外生菌根真菌增强旱柳Cd耐性的调控机制研究

Ectomycorrhizal fungi could be associated with many plant species. They play the important roles in the establishment and growth of the associated with trees. Salix matsudana may enhance the metal tolerance to Cd and accumulate the Cd after the symbiosis of the ectomycorrhizal fungi. As one of the typical tree species among the vegetation of Northern China, Salix matsudana which could be associated with many ectomycorrhizal fungi will be selected to study in this proposal. Two ectomycorrhizal fungi with different characteristics are used to inoculate Salix matsudana and Salix matsudana var. “luliu7”. The pot experiments of Salix matsudana and Salix matsudana var. “luliu7” are conducted under the treatments of three Cd levels and inoculation. The regulation effects of ectomycorrhizal fungi on the transport and accumulation of Cd, the distribution and compartment of Cd, the photosynthetic capacity of leaf, the antioxidative system of organ and the secreted organic acid from root system will be measured by chemical analysis and physiological ecology method. Meanwhile, the responses of transcript levels of functional genes about transport and detoxification in root/ectomycorrhiza to different ectomycorrhizal fungi association will be explored by molecular biological technique. The correlation between ectomycorrhizal fungus species and the Cd resistance will be clarified. The regulation pattern and mechanism of ectomycorrhizal fungi on Salix matsudana Cd resistance will be explored. The results could not only develop and enrich plant heavy metal resistance theory, but also provide important theoretical base for the selection of excellent Cd resistance ectomycorrhizal fungi and tree species which could be applied in the Cd contaminated soil.

外生菌根真菌是菌根树种定殖和生长必不可少的重要菌群，其与旱柳共生可增强旱柳耐受和富集Cd的能力，但对其调控机制尚不清楚。本研究以华北区域植被中可与多种外生菌根真菌共生的代表树种旱柳为主要研究对象，通过两种不同特性的耐Cd外生菌根真菌接种，开展三个Cd浓度下两种旱柳盆栽实验。采用化学分析、分子生物学技术和生理生态学方法，系统研究外生菌根真菌增强旱柳Cd耐性的作用：Cd的分布及微区化、旱柳叶光合能力、组织器官中抗氧化酶活性与抗氧化物含量、根系分泌有机酸的种类与数量等生理生态学特性及旱柳根/菌根系统Cd转运解毒相关功能蛋白基因转录水平对外生菌根真菌共生的响应，明确外生菌根真菌对旱柳Cd耐性的增强作用，揭示不同特性外生菌根真菌对旱柳Cd耐性的调控规律，阐明其调控机制，丰富与发展植物耐受重金属胁迫理论，为耐Cd优良外生菌根真菌的筛选和Cd污染场地植被恢复中抗性树种的选择提供重要基础理论依据。

外生菌根真菌是菌根树种定殖和生长必不可少的重要菌群，其与旱柳共生可增强旱柳耐受和富集Cd的能力，但对其调控机制尚不清楚。本研究以旱柳为主要研究对象，进行两种不同特性的耐Cd外生菌根真菌接种，开展不同Cd浓度下旱柳接种外生菌根真菌后，旱柳耐Cd能力变化及其机制。获得的主要研究结果与结论如下：（1）筛选出了耐Cd外生菌根真菌。明确了土生空团菌和乳牛肝菌耐Cd性强于彩色豆马勃和褐环乳牛肝菌，但Cd富集能力恰恰相反。外生菌根真菌对低浓度Cd与高浓度Cd胁迫的耐性机理较为不同，有机酸和铁载体共同作为菌丝细胞分泌的小分子螯合物质在应对Cd胁迫时表现出相反的应激模式；（2）Cd胁迫对四种柳树幼苗叶片的生长抑制明显高于Pb胁迫，而 Pb 胁迫对根系的生长抑制明显高于Cd胁迫，在A7和A42 中这种抑制作用尤为明显。随着Cd浓度的升高，A42、A64和A94的气孔导度和叶蒸腾速率呈现出相似的趋势，即gs升高，E也随之升高。Pb浓度显著影响了A7、A42和A94对Cd在地下部的积累以及Pb在地上部的积累;（3）褐环乳牛肝菌和土生空团菌增强旱柳Cd耐性的机理研究表明，外生菌根真菌对旱柳根/菌根功能蛋白基因转录水平的调控为通过代谢通路中关键代谢途径和相关功能基因的上调来实现。（4）研究外生菌根真菌与麻栎幼苗共生后，麻栎幼苗对Cd的耐受性增强，不同的抗氧化酶和非酶抗氧化剂之间存在复杂的相互作用，这些抗氧化成分共同形成了巨大的抗氧化体系，抵抗重金属造成的氧化损伤，尤其是幼苗体内GR、CAT、POD和APX的活性明显下降，证明这些酶活性改变可能是由于外生菌根的屏障效应减少植物对重金属的吸收，从而缓解植物细胞的过氧化应激行为。本项目完成了预期的研究目标，研究结果为外生菌根真菌与植物协同修复重金属污染环境提供重要科学依据。发表SCI索引论文11篇，中文核心期刊文章1篇。参加国内外召开的学术会议12次。培养硕士研究生11名，已毕业硕士研究生9名。