title: Responses of the model legume Medicago truncatula to the rhizobial exopolysaccharide succinoglycan.
abstract: Many species of rhizobial bacteria can invade their plant hosts and induce development of symbiotic nitrogen-fixing nodules only if they are able to produce an acidic exopolysaccharide (EPS) with certain structural and molecular weight characteristics.1-3Sinorhizobium meliloti that produces the functional form of the exopolysaccharide succinoglycan induces formation of invasion structures called infection threads in the root hair cells of its plant hosts alfalfa and Medicago truncatula. However, S. meliloti mutants that cannot produce succinoglycan are not able to induce infection thread formation, resulting in an early arrest of nodule development and in nitrogen starvation of the plant. Mounting evidence has suggested that succinoglycan acts as a signal to these host plants to permit the entry of S. meliloti. Now, our microarray screen and functional category analysis of differentially-expressed genes show that M. truncatula plants inoculated with wild type S. meliloti receive a signal to increase their translation capacity, alter their metabolic activity and prepare for invasion, while those inoculated with a succinoglycan-deficient mutant do not receive this signal, and also more strongly express plant defense genes.
authors.affiliation: Department of Biology; Massachusetts Institute of Technology; Cambridge, Massachusetts USA.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Jones
authors.forename: Graham C
authors.initials: GC
authors.lastname: Walker
references.citation: Proc Natl Acad Sci U S A. 2007 Dec 26;104(52):20996-1001
references.pmid: 18079291
references.citation: EMBO J. 2007 Sep 5;26(17):3923-35
references.pmid: 17690687
references.citation: J Bacteriol. 2007 Nov;189(21):7733-40
references.pmid: 17766412
references.citation: Cell. 1987 Nov 20;51(4):579-87
references.pmid: 2824062
references.citation: Curr Opin Plant Biol. 2006 Aug;9(4):351-7
references.pmid: 16713329
references.citation: Biol Chem. 2000 Aug;381(8):705-13
references.pmid: 11030428
references.citation: Microbiol Mol Biol Rev. 2004 Jun;68(2):280-300
references.pmid: 15187185
references.citation: Plant Physiol. 2006 Jan;140(1):221-34
references.pmid: 16377745
references.citation: J Bacteriol. 1998 Oct;180(19):5183-91
references.pmid: 9748453
references.citation: Cell. 1989 Feb 24;56(4):661-72
references.pmid: 2537152
references.citation: J Bacteriol. 2007 Dec;189(23):8741-5
references.pmid: 17921312
references.citation: Nat Rev Microbiol. 2007 Aug;5(8):619-33
references.pmid: 17632573
references.citation: J Bacteriol. 2006 Sep;188(17):6168-78
references.pmid: 16923883