New insights into Nod factor biosynthesis: Analyses of chitooligomers and lipo-chitooligomers of Rhizobium sp. IRBG74 mutants.
Soil-dwelling, nitrogen-fixing rhizobia signal their presence to legume hosts by secreting lipo-chitooligomers (LCOs) that are decorated with a variety of chemical substituents. It has long been assumed, but never empirically shown, that the LCO backbone is synthesized first by NodC, NodB, and NodA, followed by addition of one or more substituents by other Nod proteins. By analyzing a collection of in-frame deletion mutants of key nod genes in the bacterium Rhizobium sp. IRBG74 by mass spectrometry, we were able to shed light on the possible substitution order of LCO decorations, and we discovered that the prevailing view is probably erroneous. We found that most substituents could be transferred to a short chitin backbone prior to acylation by NodA, which is probably one of the last steps in LCO biosynthesis. The existence of substituted, short chitin oligomers offers new insights into symbiotic plant-microbe signaling.
Laboratoire des IMRCP, UMR 5623 Université Paul Sabatier, Toulouse, France.
Véréna
V
Poinsot
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Matthew B
MB
Crook
Laboratoire des Interactions Plantes-Microorganismes, UMR 441/2594 INRA-CNRS, B.P. 52627, F-31326 Castanet-Tolosan Cedex, France.
Stéphanie
S
Erdn
Laboratoire des Interactions Plantes-Microorganismes, UMR 441/2594 INRA-CNRS, B.P. 52627, F-31326 Castanet-Tolosan Cedex, France.
Fabienne
F
Maillet
Laboratoire des IMRCP, UMR 5623 Université Paul Sabatier, Toulouse, France.
Adeline
A
Bascaules
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; Department of Agronomy, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address: jeanmichel.ane@wisc.edu.
Jean-Michel
JM
Ané
D000215:Acylation; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002686:Chitin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D048271:Chitosan; D008070:Lipopolysaccharides / Q000235:genetics* / Q000378:metabolism; D013058:Mass Spectrometry; D015394:Molecular Structure; D009154:Mutation; D009844:Oligosaccharides; D012231:Rhizobium / Q000737:chemistry / Q000235:genetics*
D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D009844:Oligosaccharides; C493484:oligochitosan; D002686:Chitin; D048271:Chitosan
Acylation; Arabinosylation; Carbamoylation; Chitooligomers; Fucosylation; Lipo-chitooligomers