Plant chemicals to promote rhizoremediation of POP-contaminated brownfields

呼吸圈是植物根周围的区域，在那里植物和微生物之间发生复杂的相互作用。与植物根系共生的细菌被称为植物根际促生细菌（PGPR）。这种关联对两种生物都非常有益。PGPR保护植物免受疾病，并产生植物生长刺激剂。作为回报，植物分泌出有利于PGPR整体活性的化合物。渗出物含有的化学物质作为信号，促进根定植过程的PGPR和其他如类黄酮和萜烯，可能会导致分解代谢途径参与土壤有机物的降解，包括持久性污染物（POP），如多氯联苯（PCB）。因此，根际修复是植物将污染物泵入根际并释放促进根际细菌生长并诱导其POP分解代谢途径的化学物质的过程。 Rhizoremediaton是修复棕地的最合适的技术之一，因为它的成本比替代品低50%至80%，并且需要最少的干预。本建议的目标是1-确定植物根系分泌物的组分，诱导根际细菌的根定殖特性，从而促进其在土壤中的植入和生存; 2-确定分泌物组分，诱导PCB降解的PCB降解根际细菌。这些化学品将具有很高的商业价值，因为它们将提供一种额外的工具来协助植物修复过程。具体目标是：1-从十字花科植物或豆科植物中筛选具有利用苯丙素类化合物和降解持久性有机污染物双重能力的天然PGPR; 2-鉴定植物分泌物[十字花科植物]中的化学物质（拟南芥）和豆类（Medicago sativa，alfalfa plant）]作为效应子，通过PGPR诱导植物根系定殖性状; 3-评估植物根系分泌物中的化学物质对根际细菌PCB降解基因表达的影响; 4-评估目标2和目标3中确定的效应物在微观实验中的影响。

Rhizosphere is the zone surrounding plant roots where complex interactions take place between plants, and microorganisms. The bacteria living in association with plant roots are called plant growth promoting rhizobacteria (PGPR). This association is highly beneficial for both organisms. PGPR protect plants against diseases and they produce plant growth stimulators. In return, plants exude compounds that are beneficial for overall activities of PGPR. Exudates contain chemicals that act as signal to promote the root colonization process by PGPR and others such as flavonoids and terpenes that may induce catabolic pathways involved in the degradation of soil organics including persistent pollutants (POPs) such as polychlorinated biphenyls (PCBs). Therefore, rhizoremediation is a process in which plants pump contaminants to the rhizosphere and release chemicals that promote rhizobacterial growth and induce their POP catabolic pathways. Rhizoremediaton is among the most suitable technology for remediating brownsfields since its cost is 50 to 80% lower than alternatives and it requires a minimum of intervention. The objectives of this proposal are 1- to identify plant root exudates components that induce root colonization traits of rhizobacteria, thus facilitating their implantation and survival in soil; 2- to identify exudates components that induce PCB degradation by PCB-degrading rhizobacteria. These chemicals will be of high commercial value as they should provide an additional tool to assist the phytoremediation processes. The specific objectives will be 1- to screen for natural PGPR from crucifers or legumes exhibiting the dual ability of utilizing phenylpropanoids and degrading POPs; 2- To identify chemicals from plant exudates [crucifers (Arabidopsis thaliana) and legumes (Medicago sativa, alfalfa plant)] that act as effector to induce plant root colonization traits by PGPRs; 3- to evaluate the effect of chemicals from plant root exudates on expression of rhizobacterial PCB degrading genes; 4- To assess the influence of the effectors identified in objective 2 and 3 in microcosm assays.