Chemotaxis of Rhizobium spp . to a Glycoprotein Produced by Birdsfoot Trefoil Roots

Abstract

Rhizobium spp. show chemotaxis to plant root exudates. A glycoprotein has been isolated from the root exudates of birdsfoot trefoil, Lotus corniculatus, which, at micromolar concentrations, attracts six strains of rhizobia. This glycoprotein has been given the trivial name trefoil chemotactin and contains approximately twice as much protein as carbohydrate. Gel filtration of trefoil chemotactin on a Bio-Gel A-1.5m column gave a molecular weight of approximately 60,000. Trefoil chemotactin represents a new class of chemoattractants for bacteria.

Early recognition in the Rhizobium meliloti-alfalfa symbiosis: root exudate factor stimulates root adsorption of homologous rhizobia

“…Starting with the young growing root as it penetrates the soil populated by free-living rhizobia, the early events of the symbiotic process-collectively designated as preinfection-take place with the bacterial cells still outside the root tissues: they comprise rhizobial chemotactic approach to the root, root colonization, attachment to root surfaces, particularly to emerging root hairs, hair deformation and curling, and induction at a distance of a meristem and cortex proliferation at special locations or foci in the root (29,41 (3,11,20,21). In clover, enzymes in the root exudate stimulate polar attachment of R. trifolii to surfaces of root hairs (14).…”

“…Many of these exudate components are rhizobial chemoattractants (3,11,20,21). In clover, enzymes in the root exudate stimulate polar attachment of R. trifolii to surfaces of root hairs (14).…”

Two Host-Inducible Genes of Rhizobium fredii and Characterization of the Inducing Compound

“…Recently, evidence has accumulated from several laboratories indicating that some form of bacterium-plant communication is important for the early symbiotic steps (3,4,7,8,13,14,17,18,29,37; R. M. Kosslak, R. Bookland, J. Barkei, H. E. Paaren, and E. R. Applebaum, Proc. Natl.…”

“…Although the exact natures and modes of action of the excreted substances are unknown, crude soybean root exudates have been shown to stimulate chemotaxis in Bradyrhizobium sp. (14), influence lectin binding in Bradyrhizobium japonicum strains (8), elicit a faster nodulation response in Bradyrhizo-1 1 Present address: Biotechnology Center, Ohio State University, Columbus, OH 43210-1002. bium spp. strain 32H1 (7), cause a phenotypic reversion in slow-to-nodulate B. japonicum HS111 (18), induce symbiosis-associated genes in Rhizobium fredii (29), and increase the competitiveness of some B. japonicum strains (3).…”

“…Recently, evidence has accumulated from several laboratories indicating that some form of bacterium-plant communication is important for the early symbiotic steps (3,4,7,8,13,14,17,18,29,37 (7), cause a phenotypic reversion in slow-to-nodulate B. japonicum HS111 (18), induce symbiosis-associated genes in Rhizobium fredii (29), and increase the competitiveness of some B. japonicum strains (3). Both positive and negative interactions of root-or seed-derived compounds (flavanones, flavanols, flavones, and isoflavones) have been shown with the common nodulation genes of Rhizobium meliloti (28, 30), Rhizobium trifolii (22), Rhizobium leguminosarum (49), and B. japonicum (Kosslak et al, in press).…”