AUTHOR=Castellani Lucas G. , Luchetti Abril , Nilsson Juliet F. , Pérez-Giménez Julieta , Wegener Caren , Schlüter Andreas , Pühler Alfred , Lagares Antonio , Brom Susana , Pistorio Mariano , Niehaus Karsten , Torres Tejerizo Gonzalo A. 

TITLE=Exopolysaccharide Characterization of Rhizobium favelukesii LPU83 and Its Role in the Symbiosis With Alfalfa

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.642576

DOI=10.3389/fpls.2021.642576

ISSN=1664-462X

ABSTRACT=<p>One of the greatest inputs of available nitrogen into the biosphere occurs through the biological N<sub>2</sub>-fixation to ammonium as result of the symbiosis between rhizobia and leguminous plants. These interactions allow increased crop yields on nitrogen-poor soils. Exopolysaccharides (EPS) are key components for the establishment of an effective symbiosis between alfalfa and <italic>Ensifer meliloti</italic>, as bacteria that lack EPS are unable to infect the host plants. <italic>Rhizobium favelukesii</italic> LPU83 is an acid-tolerant rhizobia strain capable of nodulating alfalfa but inefficient to fix nitrogen. Aiming to identify the molecular determinants that allow <italic>R. favelukesii</italic> to infect plants, we studied its EPS biosynthesis. LPU83 produces an EPS I identical to the one present in <italic>E. meliloti</italic>, but the organization of the genes involved in its synthesis is different. The main gene cluster needed for the synthesis of EPS I in <italic>E. meliloti</italic>, is split into three different sections in <italic>R. favelukesii</italic>, which probably arose by a recent event of horizontal gene transfer. A <italic>R. favelukesii</italic> strain devoided of all the genes needed for the synthesis of EPS I is still able to infect and nodulate alfalfa, suggesting that attention should be directed to other molecules involved in the development of the symbiosis.</p>