Broad‐host‐range Rhizobium species strain NGR234 secretes a family of carbamoylated, and fucosylated, nodulation signals that are O‐acetylated or sulphated

Abstract

Rhizobium species strain NGR234 is the most promiscuous known rhizobium. In addition to the non-legume Parasponia andersonii, it nodulates at least 70 genera of legumes. Here we show that the nodulation genes of this bacterium determine the production of a large family of Nod-factors which are N-acylated chitin pentamers carrying a variety of substituents. The terminal non-reducing glucosamine is N-acylated with vaccenic or palmitic acids, is N-methylated, and carries varying numbers of carbamoyl groups. The reducing N-acetyl-glucosamine residue is substituted on position 6 with 2-O-methyl-L-fucose which may be acetylated or sulphated or non-substituted. All three internal residues are N-acetylated. At pico- to nanomolar concentrations, these signal molecules exhibit biological activities on the tropical legumes Macroptilium and Vigna (Phaseoleae), as well as on both the temperate genera Medicago (Trifoliae) and Vicia (Viciae). These data strongly suggest that the uniquely broad host range of NGR234 is mediated by the synthesis of a family of varied sulphated and non-sulphated lipo-oligosaccharide signals.

Root Hair Deformation Activity of Nodulation Factors and Their Fate on Vicia sativa

“…The first deformation occurs within 1 h after Nod factor application, whereas an increased cytoplasmic streaming occurs within 30 min (data not shown). In most other studies, root hair deformation was first scored several days after Nod factor application (Lerouge et al, 1990;Spaink et al, 1991;Price et al, 1992;Sanjuan et al, 1992;Schultze et al, 1992;Mergaert et al, 1993). Therefore, it is not clear whether such studies provide an accurate comparison of the abilities of different Nod factors to induce deformation.…”

“…105, 1994 deformation was scored 3 h after inoculation with R. leguminosarum bv trifolii and these deformed root hairs were present in a zone located 2 to 5 mm from the tip (Bhuvaneswari and Solheim, 1985). However, in a11 but one (Firmin et al, 1993) of the studies to determine Nod factor activity, root hair deformation was examined severa1 days after addition of Nod factor (Lerouge et al, 1990;Spaink et al, 1991;Price et al, 1992;Sanjuan et al, 1992;Schultze et al, 1992;Mergaert et al, 1993).…”

The NodC protein of Azorhizobium caulinodans is an N-acetylglucosaminyltransferase.

“…The first stage of this interaction leads to the activation of bacterial nodulation (nod) genes by plant flavonoids. The nod genes are involved in the production ofNod factors (1)(2)(3)(4)(5)(6), which act as host-specific signals to trigger nodule formation (1,2,5,7,8). The backbone of all Nod factors consists of an N-acetylglucosamine oligosaccharide (three to five sugar residues) from which the acetyl group at the nonreducing end is replaced by an acyl chain.…”

Mutation or Increased Copy Number of nodE Has No Effect on the Spectrum of Chitolipooligosaccharide Nod Factors Made By Rhizobiumleguminosarum bv. trifolii

“…It was originally thought that Rhizobium synthesizes only minute quantities of CLOSs and excretes them into the extracellular milieu where they can act on the host plant (3,4,13). However, we recently found that CLOS glycolipids can be purified in significantly higher yield (Ͼ1000-fold) from extracts of cell membranes of wild-type rhizobia than from culture supernatants (14,15).…”