S153: Beneficial rhizobacteria drive photosynthetic efficiency increases in Arabidopsis

Plant growth-promoting rhizobacteria are naturally occurring soil microorganisms that colonize roots and stimulate plant growth. Although such beneficial bacteria have been applied to a wide range of agricultural crops for the purpose of growth enhancement, the biochemical complexity of such plant-microbe interactions have limited our mechanistic understanding of bacterial-induced plant growth promotion. Using a simplified experimental design in which the bacterial stimulus is limited to volatile components, we have begun to characterize initial chemical signals from the commercial strain Bacillus subtilis GB03 as well as down-stream molecular and physiological plant responses involved in inducible growth promotion in Arabidopsis.  Here we provide biochemical evidence that GB03 regulates photosynthesis through modulation of endogenous sugar/ABA-signaling and iron acquisition to increase photosynthetic efficiency as well as chlorophyll content thereby establishing a regulatory role for soil symbionts in plant acquisition of energy.