Growth temperature regulation of host-specific modifications of rhizobial lipo-chitin oligosaccharides: the function of nodX is temperature regulated.
Lipo-chitin oligosaccharides (LCOs) are usually produced and isolated for structural analysis from bacteria cultured under laboratory rather than field conditions. We have studied the influence of bacterial growth temperature on the LCO structures produced by different Rhizobium leguminosarum strains, using thin-layer chromatographic, high-performance liquid chromatographic, and mass spectrometric analyses. Wild-type R. leguminosarum bv. viciae A1 was shown to produce larger relative amounts of nodX-mediated, acetylated LCOs at 12 degrees C than at 28 degrees C, indicating that the activity of nodX (a gene encoding an LCO O-acetyl transferase) is temperature dependent. Interestingly, symbiotic resistance genes sym1 and sym2 found in primitive pea cultivars are also temperature sensitive, only being active at low temperatures, at which they block nodulation by R. leguminosarum bv. viciae strains lacking nodX. We therefore propose that the gene-for-gene relationship between plant and bacterium has a temperature-sensitive mechanism as an adaptation to environmental conditions. An R. leguminosarum bv. trifolii strain was also shown to produce larger relative amounts of nodX-mediated, acetylated LCOs at 12 degrees C than at 28 degrees C. The major components synthesized by the two strains are produced at both temperatures but in different relative amounts, while some minor components are only produced at one of the two temperatures.
Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research, Utrecht University, The Netherlands.
M M
MM
Olsthoorn
E
E
Stokvis
J
J
Haverkamp
H P
HP
Spaink
J E
JE
Thomas-Oates
D001426:Bacterial Proteins / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016961:Rhizobium leguminosarum / Q000254:growth & development / Q000378:metabolism*; D013696:Temperature
D001426:Bacterial Proteins; D008070:Lipopolysaccharides; C089833:NodX protein, Rhizobium leguminosarum; C023023:lipid-linked oligosaccharides