植物根际促生菌Pseudomonas fluorescens 2P24感受与响应类黄酮的分子机制研究

The mechanism of interaction between rhizosphere microorganisms and biological environments are one of the hot spots in the microbial ecology research. Plant growth-promoting rhizobacteria (PGPR) are important components of rhizosphere microbial communities, and play very important roles in plant growth, development and disease resistance. Previous studies have shown that flavonoids secreted into rhizosphere by plants act as signaling molecules that regulate the physiological activities of some plant symbiotic bacteria. However, there is still lack of systematic and in-depth studies of the sensing and response mechanisms of flavonoids by PGPR. In this project, we will take the Pseudomonas fluorescens 2P24 as a representative PGPR. By using the transcriptome and proteomics methods combined with phenotype (eg. production of secondary metabolites and biofilm formation) characterization , we will determine the signaling roles of the typical flavonoids such as phloretin, quercetin and apigenin and elucidate the response mechanism of the 2P24 strains to flavonoids . On the other hand, we will try to identify the transcription factors capable of binding flavonoids and their downstream effector genes, providing insights to the biological functions of these genes as well as the sensing mechanisms of flavonoids. Taken together, this project will not only deepen our understanding of the molecular mechanism of PGPR-plant interactions, but provide guidance for the application of PGPR in agriculture as well.

根际微生物与生物环境间的相互作用方式与机制是当今微生物生态学研究的热点，对于植物根际促生菌促进植物生长、发育和提高抗性方面的研究具有重要的理论和实践价值。前期研究表明，植物根际分泌的类黄酮作为信号分子影响和调控一些植物共生菌的生理活动。但是，对根际促生菌感受与应答类黄酮的分子机制目前还缺乏系统而深入的研究。本项目中我们将以根际促生菌—荧光假单胞菌2P24为例，通过转录组学和蛋白质组学等系统生物学手段，并结合次生代谢产生生成和生物膜形成等微生物生理指标的测定，确定典型的类黄酮如根皮素、槲皮素和芹菜素等的信号分子作用，系统的揭示2P24菌株对类黄酮的应答机制。另一方面，我们将鉴定结合类黄酮的转录因子及下游调控基因，阐明这些基因的生物学功能以及对类黄酮分子的感受方式和机制。该项目将加深我们对根际促生菌—植物互作的分子机制的理解，同时也能为根际促生菌在农业生产中的应用提供一定的理论指导。

植物根际分泌物在植物-微生物互作过程中发挥着重要作用。已知豆科植物通过分泌类黄酮来吸引固氮根瘤菌，并诱导根瘤菌结瘤。对植物病原菌，如丁香假单胞菌DC3000和铜绿假单胞菌，类黄酮可作为信号分子抑制III型分泌系统和群体感应，从而降低其致病性。但是，目前对根际促生菌的感受和响应类黄酮的分子机制仍然知之甚少。本项目中，我们以根际促生菌—荧光假单胞菌2P24为例，对根际促生菌感受并响应植物类黄酮分子的机制进行了探究，通过蛋白质组学等手段，并结合次生代谢产生生成和生物膜形成等微生物生理指标的测定，确定了典型的类黄酮如根皮素和芹菜素可作为信号分子影响2P24菌株的多种生理过程；鉴定出转录调控因子AefR和PhlH能够感受胞外的类黄酮，调控2P24菌株的群体感应和次生代谢产物2,4-DAPG的生成。这些工作加深了我们对根际促生菌—植物互作的分子机制的理解，同时也能为根际促生菌在农业生产中的应用提供一定的理论指导。