Exopolysaccharide structure is not a determinant of host-plant specificity in nodulation of Vicia sativa roots.
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.
Laus
Marc C
MC
Institute of Biology Leiden, Leiden University, The Netherlands.
van Brussel
Anton A N
AA
Kijne
Jan W
JW
D002240:Carbohydrate Sequence; D003227:Conjugation, Genetic; D008070:Lipopolysaccharides / Q000096:biosynthesis; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000235:genetics; D016961:Rhizobium leguminosarum / Q000737:chemistry / Q000502:physiology*; D013045:Species Specificity; D013329:Structure-Activity Relationship; D013559:Symbiosis; D014169:Transformation, Bacterial; D033022:Vicia sativa / Q000382:microbiology*
D008070:Lipopolysaccharides; C092736:Nod factor, Rhizobium leguminosarum; D011135:Polysaccharides, Bacterial