Exopolysaccharide structure is not a determinant of host-plant specificity in nodulation of Vicia sativa roots

• Published in: Molecular plant-microbe interactions Vol. 18; no. 11; pp. 1123 - 1129
• Main Authors: Laus, M.C, Brussel, A.A.N. van, Kijne, J.W
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01-11-2005; The American Phytopathological Society
• Subjects: Agronomy. Soil science and plant productions; Bacterial plant pathogens; Biological and medical sciences; Carbohydrate Sequence; carbohydrate structure; Conjugation, Genetic; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Lipopolysaccharides - biosynthesis; Molecular Sequence Data; nitrogen-fixing bacteria; nodulation; Phytopathology. Animal pests. Plant and forest protection; Plant Roots - microbiology; polysaccharides; Polysaccharides, Bacterial - chemistry; Polysaccharides, Bacterial - genetics; Rhizobium leguminosarum; Rhizobium leguminosarum - chemistry; Rhizobium leguminosarum - physiology; root nodules; soil bacteria; Species Specificity; Structure-Activity Relationship; symbionts; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Transformation, Bacterial; Vicia sativa - microbiology; Vicia sativa subsp. nigra; Symbiosis; Wolbachieae; Root; Growth rate; Nodulation; Plant nodule; Rhizobium leguminosarum; Symbiont; Incidence; Strain; Rickettsiales; Plasmid; Vicia sativa; Specificity; Leguminosae; Gene; Dicotyledones; Angiospermae; Bacteria; Spermatophyta; Fodder crop; Rhizobiaceae; Mutation; Symbiotes
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-18-1123

Exopolysaccharide (EPS)-deficient strains of the root nodule symbiote Rhizobium leguminosarum induce formation of abortive infection threads in Vicia sativa subsp. nigra roots. As a result, the nodule tissue remains uninfected. Formation of an infection thread can be restored by coinoculation of the EPS-deficient mutant with a Nod factor-deficient strain, which produces a similar EPS structure. This suggests that EPS contributes to host-plant specificity of nodulation. Here, a comparison was made of i) coinoculation with heterologous strains with different EPS structures, and ii) introduction of the pRL1JI Sym plasmid or a nod gene-encoding fragment in the same heterologous strains. Most strains not complementing in coinoculation experiments were able to nodulate V. sativa roots as transconjugants. Apparently, coinoculation is a delicate approach in which differences in root colonization ability or bacterial growth rate easily affect successful infection-thread formation. Obviously, lack of infection-thread formation in coinoculation studies is not solely determined by EPS structure. Transconjugation data show that different EPS structures can allow infection-thread formation and subsequent nodulation of V. sativa roots.