Suntory Foundation for Life Sciences Kyoto, Kyoto, Japan
Abstract Text: In natural environments, plant physiology is shaped by fluctuating nutrient availability and the presence of surrounding microorganisms. While direct physical interactions between plants and microbes have been extensively studied, non-physical interactions, such as volatile compound-mediated signaling, remain largely unexplored. In this study, we isolated a strain of Pseudomonas aeruginosa (Pso) from the roots of healthy Arabidopsis thaliana colonized by the beneficial endophytic fungus Colletotrichum tofieldiae (Ct), which influences root-associated bacterial communities. We observed a significant inhibition of Arabidopsis seedling growth when Pso was cultured on a separate plate containing nutrient-rich medium, suggesting that volatile compounds produced by Pso mediate this interaction. Intriguingly, when Pso was cultivated on nutrient-poor medium, its presence instead promoted plant growth, particularly under low-phosphate (Pi) conditions. Notably, genetic analyses revealed that Pso-mediated plant growth inhibition, but not growth promotion, depends on the bacterial quorum sensing pathway. Further, we found that Pso on beneficial mode decreased the colonization level of Ct in the root. These findings suggest that tripartite interactions among plants, Ct, and Pso can be either beneficial or detrimental, operating along the mutualism-parasitism continuum. In this presentation, we will also discuss the potential mechanisms by which bacterial volatiles promote plant growth.
