多环芳烃从作物根表向地上部的转运机制研究

Polycyclic aromatic hydrocarbons (PAHs) are an important group of widespread environmental pollutants. These compounds have been of major health concern due to their well-documented carcinogenicity, mutagenicity and toxicity to both humans and non-human organisms. Dietary intake of plant-based foods is a major contribution to the total exposure of PAHs. Thereby, it is essential to understand the exact process of PAH transport from root surface to shoot for governing the crop contamination by PAHs and improving the phytoremediation of PAH-contaminated soil or water. However, the mechanism underlying acropetal translocation of PAHs from crop root surface remains unclear. .Our hypothesis is that apoplast and symplast are involved in root short-distance transport of PAHs, and the long-distance acropetal transport of PAHs is mainly via phloem. The objectives of this project are to reveal the short-distance and long-distance transport of PAHs from crop root surface to shoot, and to evaluate the contributions of apoplast/symplast and xylem/phloem to total root PAH uptake and to long-distance transport, respectively. Batches of hydroponic experiment will be employed. The apoplastic and symplastic uptake of PAHs will be investigated by the vacuum-infiltration-centrifugation method. Computation combined quantum mechanics with molecular mechanics (QM/MM), confocal fluorescence microscopy and proteomic analysis will be used to study the xylem loading of PAHs, the identification of special protein and the binding mechanism of PAHs and special protein, respectively. The phloem pathway for PAH acropetal translocation in crops will also be confirmed in the project. .The expected results of the project will provide not only novel insights into the mechanisms on the uptake and acropetal translocation of PAHs in plants, but also the help to optimize strategies for crop safety and phytoremediation of PAH-contaminated soil/water.

多环芳烃（PAHs）具有强致癌、致畸和致突变效应，农产品是人类PAHs暴露的主要途径。然而，PAHs如何从作物根表转运至地上部迄今尚未明晰。本项目拟采用近年来发展的并已在生态学、环境学、化学、生物学和土壤学领域成功运用的新方法和新技术（如量子化学计算模拟技术、激光共聚焦显微技术、蛋白质组学技术和本课题组建立的真空渗透离心法等），通过作物水培试验研究根系质外体/共质体吸收PAHs的特征与贡献、木质部装卸过程、伤流液中特异蛋白的鉴别及其在运输过程中的作用和验证韧皮部长距离向上运输的假设，并进行土培试验佐证，拟从分子水平揭示PAHs从作物根表向地上部传输的机制，为阻控PAHs进入农产品尤其是作物的可食部位和PAHs污染环境植物修复的强化提供策略。

多环芳烃（PAHs）具有强的“三致”作用（致癌、致畸、致突变），农产品的摄入是人类PAHs暴露的主要途径。然而，PAHs如何从作物根表向地上部转运至今未明。本项目主要采用双光子荧光激发显微、纳米磁珠免疫分析、蛋白质组学和分子拼接等技术，通过水培和土培试验主要研究了PAHs在作物体内的运输与分布、根系PAHs质外体和共质体的吸收特征、木质部PAHs的装载及其向上运输的机制，同时验证了PAHs韧皮部向上长距离运输的假设。研究发现苗期与灌浆期是小麦根系PAHs吸收和转运的关键期，低环PAHs根系向籽粒的迁移作用大于叶片向籽粒的迁移作用。根系质外体和共质体PAHs的吸收动力学遵循Elovich方程，质外体和共质体吸收的浓度依赖性则分别符合Langmuir和Michaelis-Menten方程，共质体吸收（>55%）贡献大于质外体（<45%）。H+-ATPase参与了PAHs自根系木质部薄壁细胞到导管的主动装载过程，PAHs可通过韧皮部向地上部运输。过氧化物酶（A0A3B5XXD0）和非典型蛋白（A0A3B6LUC6）是小麦木质部汁液中菲的转运蛋白，过氧化物酶-菲复合物是通过疏水作用与ALA71、ILE74、ARG75、ALA205、PHE208和LEU257残基及π-堆叠作用与HIS206残基结合而成，非典型蛋白-菲复合物则是通过疏水作用与THR241、PHE245、ASP309和TYR381残基结合形成，其结合能分别为-6.42和-6.16 kcal mol-1。叶缘PAHs含量高于叶中，叶脉大于叶肉。菲抑制类囊体基因表达造成叶绿体结构破坏，进而加速了叶绿素的降解，导致小麦叶片黄化，施用外源类胡萝卜素可以缓解菲对小麦生长发育的影响。菲暴露下，miR398靶向CSD1/CSD2调控小麦根系的抗氧化过程，miR164靶向NAC转录因子调节小麦根系生长和不定根的产生。项目研究结果在理论上揭示了PAHs从作物根表至地上部的转运机理，在实践上为农产品安全生产的保障和PAHs污染环境植物修复的强化提供了依据和技术策略，具有非常广阔的应用前景。