(785f) Mechanisms and Adaptation of the Arabidopsis thaliana Root Microbiota in Iron Mobilization and Uptake from Iron-Limiting Environments

Plants coexist with a diverse community of microbes, some of which assist the plant in overcoming poor nutrient availability in low quality soils. For example, nitrogen fixation is made possible by the nodule-forming rhizobia, and otherwise inaccessible phosphorous is provided to the plant by their root-associated fungi. However, little is known about the extent to which the natural root microbiota facilitates the uptake of the fourth-most limiting nutrient in agriculture: iron. Moreover, a systematic study of how the root-associated microbiota adapts to such low quality conditions, and the impact such adaptation may have on the plantâ??s nutrient status remains poorly understood.

We have identified root-associated bacteria that promote the growth and development of Arabidopsis thaliana under conditions simulating low iron availability in vitro. These strains, which represent members within the phyla Proteobacteria and Bacteroidetes, are employed as models to investigate the mechanics facilitating plant iron acquisition by its microbiota. By applying reverse genetics and metabolomics, I investigate the role of the plantâ??s secondary metabolism in mediating plant-microbe signaling in the rhizosphere. In parallel, I investigate adaptation of the A. thaliana root microbiota to calcareous soils, which constitute approximately one-third of the worldâ??s arable land. I will apply root-associated bacterial and fungal community profiling methods to determine adaptation in terms of community composition, and cross-reference these results with comparative genomics and plant growth promoting ability of a comprehensive rhizobacterial library derived from this soil type. Finally, I use a plant gnotobiotic system to investigate whether defined bacterial communities obtained from a calcareous soil uniquely display an ability to promote plant growth under iron-limiting conditions.