土壤中十溴二苯乙烷(DBDPE)的植物吸收传输特征及微观机制研究

采用温室土培实验，研究了土壤中新型溴代阻燃剂十溴二苯乙烷（DBDPE）在不同种属植物中的吸收和传输特征，以及植物脂的影响作用；进一步应用计算模拟的手段解析了植物载脂蛋白与DBDPE的分子间相互作用，以阐明DBDPE的植物吸收传输的微观机制.结果表明，在玉米、小麦和黄瓜3种植物的根和地上部均检测到了DBDPE，根中DBDPE的含量高出地上部1~2个数量级.植物中累积的DBDPE量随时间的变化存在明显的生长稀释效应（p<0.05）.DBDPE的根吸收和茎向传输表现出植物种属间的显著差异（p<0.05），根富集因子（RCF）顺序为黄瓜（0.30~0.57） > 小麦（0.10~0.39） > 玉米（0.03~0.26），而传输系数（TF）为小麦（0.17~0.20） > 玉米（0.16~0.19） > 黄瓜（0.04~0.07）.DBDPE的根吸收量及RCF值与植物根脂含量成显著正相关关系（r=0.94，p<0.01；r=0.98，p<0.01）；其地上部累积量及TF值与植物地上部脂含量显著正相关（r=0.77，p<0.05；r=0.94，p<0.05），但与植物根脂含量呈显著负相关关系（r=-0.74，p<0.05；r=-0.76，p<0.05），说明脂是控制植物吸收和传输DBDPE的重要组分.分子对接的结果显示，DBDPE能键合进入3种植物载脂蛋白的活性区域并与载脂蛋白特异性的活性位点作用，且DBDPE与载脂蛋白的结合方式及结合能力存在植物种属的显著差异，两者的结合强弱与根吸收DBDPE能力的顺序一致，印证了实验结果.本研究有助于理解植物中DBDPE的吸收传输特征及机制，可为深入认识DBDPE的陆生生态环境行为提供重要依据.

Plant uptake and translocation of DBDPE in soil and the micro-mechanisms

Plant uptake and translocation of decabromodiphenyl ethane (DBDPE), one of the novel brominated flame retardants, in the soil were investigated in a greenhouse study. Effects of lipids on DBDPE accumulation in plants were evaluated. In order to clarify the micro-mechanisms, molecular interactions of DBDPE with plant lipid transfer proteins (LTPs) were further characterized by the method of computer simulation. The results showed that accumulation of DBDPE were observed in both the roots and the aboveground parts of all the three plant species examined, namely maize, wheat and cucumber. Concentrations of DBDPE in roots were 1~2 orders of magnitude higher than those in the aboveground parts of plants. Plant growth dilution had a significant effect (p<0.05) on the time-dependent accumulation of DBDPE in plant tissues. Root concentration factors (RCFs) for DBDPE were followed the order of cucumber (0.30~0.57) > wheat (0.10~0.39) > maize (0.03~0.26); whereas the translocation factors (TFs) were wheat (0.17~0.20) > maize (0.16~0.19) > cucumber (0.04~0.07). Root uptake of DBDPE and its RCFs were positively correlated with root lipid content (r=0.94,p<0.01;r=0.98,p<0.01). Concentrations of DBDPE in the aboveground parts of plants and its TFs were positively correlated with the lipid contents in the aboveground parts(r=0.77,p<0.05;r=0.94,p<0.05), but were inversely related to root lipid contents(r=-0.74,p<0.05;r=-0.76,p<0.05). Lipid was thus evidenced to be an essential component that controlled the uptake and translocation of DBDPE in plants. Molecular docking results showed that DBDPE could be docked into the active cavities of three plant LTPs and bound to their specific residues in the active sites. In addition, binding modes and binding affinities of LTPs to DBDPE were significantly difference among three plant species, and the binding abilities of LTPs were consistent with the root uptake of DBDPE in plants, which confirmed the experimental results. This study is beneficial to understand the characteristics and mechanisms of DBDPE uptaken and translocated by plants, and will provide vital basis on the in-depth exploration of the behaviors of DBDPE in the terrestrial eco-environment.