Three unusual modifications, a D-arabinosyl, an N-methyl, and a carbamoyl group, are present on the Nod factors of Azorhizobium caulinodans strain ORS571
1993
Mergaert, P. | Montagu, M. van | Prome, J.C. | Holsters, M.
Azorhizobium caulinodans strain ORS571 is a symbiont of the tropical legume Sesbania rostrata. Upon nod gene induction with naringenin, strain ORS571 secretes into the culture medium Nod factors that morphologically change the host plant-in particular, deformed root hairs (Hai/Had) and meristematic foci are formed at the basis of lateral roots. The latter infrequently develop further into nodule-like structures. The azorhizobial Nod factors are chitin tetramers or pentamers, N-acylated at the nonreducing-end glucosamine with either vaccenic acid (C18:1) or stearic acid (C18:0). They, thus, resemble the previously described Nod factors from (brady)rhizobia. The backbone lipooligosaccharide is substituted with unusual modifications, presumably involved in host-specificity determination. There is a D-arabinose branch on the reducing end and an N-methyl and O-carbamoyl substitution on the nonreducing end of the oligosaccharide chain. The previously identified nod gene nolK may be involved in the synthesis of a D-arabinose derivative. The nodS gene product is probably responsible for the N-methylation of Nod factors.
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