Unravel the role of quorum sensing in driving plant-microbial interactions

The plant immunity and microbiome play vital roles in promoting the growth of agriculturally important crops. However, major knowledge gaps exist which hamper their translational potentials in the field. The long-term goal of our research program is to develop the knowledge basis for harnessing plant immunity and healthy microbiome to contribute to increasing crop yield and quality. My lab pioneers the investigation of the interactions between the non-model canola (Brassica napus) and Pseudomonas aeruginosa, a common soil resident that colonizes plant roots. Our preliminary investigation identified that the P. aeruginosa quorum sensing (QS)-controlled protease IV (PIV) enhanced pattern triggered immunity (PTI) elicited by microbe-associated molecular patters (MAMPs). Moreover, colonization of P. aeruginosa to the canola root altered the rhizosphere microbiome composition and led to enhanced host fitness. On the other hand, reducing canola ethylene alleviated disease symptoms by limiting P. aeruginosa QS. These discoveries support a central hypothesis that QS modulates canola health by boosting immunity and impacting the rhizosphere microbiome. The immediate goal of this project is to dissect the details in the dynamic interplays between P. aeruginosa QS, canola immunity and rhizosphere microbiome. There are three specific objectives: 1. To assess the synergistic activation of PTI by P. aeruginosa QS-controlled PIV with MAMPs. We discovered a distinct PIV pathway that has a synergistic effect with MAMPs on defense gene induction. We propose to study the detailed interactions between MAMPs and PIV signaling pathways and the subsequent net defense response to test the hypothesis that P. aeruginosa QS functions synergistically with MAMPs to elicit a fully developed PTI response. 2. To define a healthy microbiome shaped by P. aeruginosa QS to increase crop yield. We will use high throughput sequencing and machine learning to identify the effects of specific P. aeruginosa QS branches on microbial components of the soil microbiome that are associated with improved plant health. Key beneficial microbes will be isolated and compiled into a consortium of healthy microbes to confirm the plant growth-promoting activity. 3. To characterize the effects of ethylene on P. aeruginosa QS and impacts on canola microbiome and functionality. Preliminary data showed that limiting ethylene synthesis decreased disease severity and QS molecule production but not bacterial colonization. We will use a combination of transcriptomic, proteomics, metabolomic and imaging flow analyses to investigate the influences of reduced canola ethylene on P. aeruginosa and subsequently on microbiome structure and functionality. Impact: we will unravel the crosstalk between bacterial QS and the plant hormone ethylene that shapes plant immunity and microbiome. This work will establish the knowledge basis for the development of precision crop microbiome management to promote crop health.