Changes in the glycosylation pattern at the reducing end of azorhizobial Nod factors affect nodulation efficiency

Fernandez-Lopez, M.; D'Haeze, W.; Montagu, M. van; Holsters, M.

Changes in the glycosylation pattern at the reducing end of azorhizobial Nod factors affect nodulation efficiency

1998

Fernandez-Lopez, M. | D'Haeze, W. | Montagu, M. van | Holsters, M.

The Nod factors of Azorhizobium caulinodans ORS571 are lipo-chitooligosaccharides that at the reducing end can be unsubstituted, substituted with a L-fucosyl group, with a D-arabinose, or with both groups at the same time. These lipochitooligosaccharides are the compounds produced by the bacteria during the signal exchange with their host plant at the onset of the nodulation process. By the use of wild-type and mutant strains, the role of the different Nod factor glycosylations on the nodulation behavior was checked. The mere presence of the D-arabinosyl group at the reducing end of the lipochitooligosaccharides resulted in a higher number of nodules on roots of Sesbania rostrata, whereas the presence or absence of L-fucose had no effect. The situation is the opposite in other tropical legumes that respond to A. caulinodans ORS571: the L-fucose is the major determinant of nodulation, whereas the presence of D-arabinose is less significant. By the use of a beta-glucuronidase reporter fusion, A. caulinodans ORS571 was shown to colonize nodules or nodule-like tissues induced on cowpea and bean, respectively.

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