Genome-wide Identification of Bacterial Plant Colonization Genes
B. COLE (1), M. Feltcher (2), R. Waters (1), K. Wetmore (3), M. Price (3), E. Ryan (1), G. Wang (1), S. Ul-Hasan (4), Y. Yoshikuni (1), R. Malmstrom (1), A. Deutschbauer (3), J. Dangl (2), A. Visel (1) (1) DOE-Joint Genome Institute, U.S.A.; (2) University of North Carolina, Chapel Hill, U.S.A.; (3) Lawrence Berkeley National Laboratory, U.S.A.; (4) University of California, Merced, U.S.A.

Plant-associated bacteria affect diverse aspects of plant growth and health.  A thorough understanding of how these microbes colonize their hosts is critical for targeted bioengineering, but the molecular mechanisms underlying colonization remain incompletely understood. To systematically investigate genes involved in root colonization in vivo, we employed a transposon-mediated genome-wide mutagenesis strategy (Bar-Seq) to study colonization of Arabidopsis thaliana roots by a Pseudomonas fluorescens strain known to colonize roots and stimulate defense against leaf pathogens. We identified 340 P. fluorescens genes whose inactivation diminished or enhanced the ability of the strain to colonize A. thaliania. Some mutations affected functions known to be required for root colonization, such as motility and carbohydrate metabolism, whereas many encode proteins with hitherto unknown functions or with predicted functions unrelated to plant association. To further characterize these genes, we assayed the same mutagenesis library under 88 in vitro conditions, linking many of the genes required for root colonization to defined functions. Our results demonstrate that saturation mutagenesis via Bar-Seq can inform high-resolution maps of complex bacterial functions important to plant ecosystems. The substantial set of plant root colonization genes identified through this screen offers a starting point for targeted improvement of the colonization capabilities of beneficial microbes.

Abstract Number: P2-18
Session Type: Poster