Link to home

Exopolysaccharide Structure Is Not a Determinant of Host-Plant Specificity in Nodulation of Vicia sativa Roots

November 2005 , Volume 18 , Number  11
Pages  1,123 - 1,129

Marc C. Laus , Anton A. N. van Brussel , and Jan W. Kijne

Institute of Biology Leiden, Leiden University, Wassenaarseweg 64, 2333AL Leiden, The Netherlands

Go to article:
Accepted 28 June 2005.

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.

© 2005 The American Phytopathological Society