The Sinorhizobium meliloti EmrR Regulator Is Required for Efficient Colonization of Medicago sativa Root Nodules

Santos, Mário R.; Marques, Andreia T.; Becker, Jörg D.; Moreira, Leonilde M.

http://hdl.handle.net/10400.7/711

Use this identifier to reference this record.

Name:	Description:	Size:	Format:
mpmi-09-13-0284-r.pdf	artigo principal	1.31 MB	Adobe PDF	Download

Send Feedback

Authors

Abstract(s)

The nitrogen-fixing bacterium Sinorhizobium meliloti must adapt to diverse conditions encountered during its symbiosis with leguminous plants. We characterized a new symbiotically relevant gene, emrR (SMc03169), whose product belongs to the TetR family of repressors and is divergently transcribed from emrAB genes encoding a putative major facilitator superfamily-type efflux pump. An emrR deletion mutant produced more succinoglycan, displayed increased cell-wall permeability, and exhibited higher tolerance to heat shock. It also showed lower tolerance to acidic conditions, a reduced production of siderophores, and lower motility and biofilm formation. The simultaneous deletion of emrA and emrR genes restored the mentioned traits to the wild-type phenotype, except for survival under heat shock, which was lower than that displayed by the wild-type strain. Furthermore, the ΔemrR mutant as well as the double ΔemrAR mutant was impaired in symbiosis with Medicago sativa; it formed fewer nodules and competed poorly with the wild-type strain for nodule colonization. Expression profiling of the ΔemrR mutant showed decreased expression of genes involved in Nod-factor and rhizobactin biosynthesis and in stress responses. Expression of genes directing the biosynthesis of succinoglycan and other polysaccharides were increased. EmrR may therefore be involved in a regulatory network targeting membrane and cell wall modifications in preparation for colonization of root hairs during symbiosis.

Keywords

Amino Acid Sequence Bacterial Adhesion Bacterial Proteins Biofilms Gene Deletion Gene Expression Regulation, Bacterial Medicago sativa Movement Plant Root Nodulation Sinorhizobium meliloti

URI

http://hdl.handle.net/10400.7/711

Citation

The Sinorhizobium meliloti EmrR Regulator Is Required for Efficient Colonization of Medicago sativa Root Nodules Mário R. Santos, Andreia T. Marques, Jörg D. Becker, and Leonilde M. Moreira Molecular Plant-Microbe Interactions 2014 27:4, 388-399