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Journal of Bacteriology, February 1999, p. 957-964, Vol. 181, No. 3
Laboratoire de Biologie Moléculaire des
Plantes Supérieures, Université de Genève, 1292 Chambésy, Geneva, Switzerland,1 and
Institut de Pharmacologie et de Biologie Structurale, CNRS,
31077 Toulouse Cedex, France2
Received 8 July 1998/Accepted 13 November 1998
Following (iso)flavonoid induction, nodulation genes of the
symbiotic nitrogen-fixing bacterium Rhizobium sp. strain
NGR234 elaborate a large family of lipooligosaccharidic Nod factors
(NodNGR factors). When secreted into the rhizosphere of
compatible legumes, these signal molecules initiate root hair
deformation and nodule development. The nonreducing glucosamine residue
of NodNGR factors are N acylated, N methylated, and mono- or
biscarbamoylated, while position C-6 of the reducing extremity is
fucosylated. This fucose residue is normally 2-O methylated and either
sulfated or acetylated. Here we present an analysis of all acetylated
NodNGR factors, which clearly shows that the acetate group may occupy
position C-3 or C-4 of the fucose moiety. Disruption of the
flavonoid-inducible nolL gene, which is preceded by a
nod box, results in the synthesis of NodNGR factors that
lack the 3-O- or 4-O-acetate groups.
Interestingly, the nodulation capacity of the mutant
NGR
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
NolL of Rhizobium sp. Strain NGR234
Is Required for O-Acetyltransferase Activity
nolL is not impaired, whereas introduction of the
nod box::nolL construct into the
related strain Rhizobium fredii USDA257 extends the
host range of this bacterium to Calopogonium caeruleum,
Leucaena leucocephala, and Lotus
halophilus. Nod factors produced by a USDA257(pnolL)
transconjugant were also acetylated. The nod
box::nolL construct was also introduced into
ANU265 (NGR234 cured of its symbiotic plasmid), along with extra copies
of the nodD1 gene. When permeabilized, these cells possessed acetyltransferase activity, although crude extracts did not.
*
Corresponding author. Mailing address: LBMPS,
Université de Genève, 1 ch. de l'Impératrice, 1292 Chambésy/Geneva, Switzerland. Phone: 41 (22) 906 17 40. Fax: 41 (22) 906 17 41. E-mail: broughtw{at}sc2a.unige.ch.
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