Plant chemicals to promote rhizoremediation of POP-contaminated brownfields

根际是植物根部周围的区域，在这里植物和微生物之间发生复杂的相互作用。与植物根共生的细菌称为植物生长促进根际细菌(PGPR)。这种联系对两种生物都是非常有益的。PGPR保护植物免受疾病侵袭，并产生植物生长刺激剂。反过来，植物会分泌出有利于PGPR整体活动的化合物。分泌物中含有的化学物质可以作为信号，促进PGPR和其他物质，如黄酮类和萜类的根定植过程，这些化学物质可能会诱导参与土壤有机物降解的分解代谢途径，包括持久性污染物(POPs)，如多氯联苯(PCbs)。因此，根际修复是植物向根际排放污染物并释放促进根际细菌生长和诱导其POP分解代谢途径的化学物质的过程。根际修复技术是最适合修复棕地的技术之一，因为它的成本比替代技术低50%至80%，而且需要的干预最少。这项建议的目标是1-鉴定诱导根际细菌根定植特性的植物根分泌物成分，从而促进它们在土壤中的种植和生存；2-鉴定通过降解多氯联苯的根际细菌诱导多氯联苯降解的分泌物成分。这些化学品将具有很高的商业价值，因为它们应该提供一个辅助植物修复过程的额外工具。具体目标将是：1-从十字花科植物或表现出利用苯丙烷类化合物和降解POP双重能力的豆类植物中筛选天然PGPR；2-从植物分泌物[十字花科植物(拟南芥)和豆科植物(紫花苜蓿、紫花苜蓿)]中鉴定可作为PGPR诱导植物根部定植特性的效应物的化学物质；3-评估植物根部分泌物中的化学物质对根际细菌多氯联苯降解基因表达的影响；4-在微观分析中评估目标2和3中确定的效应物的影响。

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.