MUTATION OR INCREASED COPY NUMBER OF NODE HAS NO EFFECT ON THE SPECTRUM OF CHITOLIPOOLIGOSACCHARIDE NOD FACTORS MADE BY RHIZOBIUM-LEGUMINOSARUM BV TRIFOLII

The bacterial gene nodE is the key determinant of host specificity in the Rhizobium leguminosarum-legume symbiosis and has been proposed to determine unique polyunsaturated fatty acyl moieties in chitolipooligo saccharides (CLOS) made by the bacterial symbiont, We evaluated nodE f unction by examining CLOS structures made by wild-type R, leguminosaru m by. trifolii ANU843, an isogenic nodE::Tn5 mutant, and a recombinant strain containing multiple copies of the pSym nod region of ANU843, H -1-NMR, electrospray ionization mass spectrometry, fast atom bombardme nt mass spectrometry, flame ionization detection-gas chromatography, g as chromatography/mass spectrometry, and high performance liquid chrom atography/UV photodiode array analyses revealed that these bacterial s trains made the same spectrum of CLOS species. We also found that ions in the mass spectra which were originally assigned to nodE-dependent CLOS species containing unique polyunsaturated fatty acids (Spaink, H, P., Bloemberg, G, V,, van Brussel, A A, N., Lugtenberg, B, J, J,, van der Drift, K.M.G.M., Haverkamp, J,, and Thomas-Gates, J, E, (1995) Mo l, Plant-Microbe Interact, 8, 155-164) were actually due to sodium add ucts of the major nodE-independent CLOS species, No evidence for nodE- dependent CLOSs was found for these strains. These results indicate a need to revise the current model to explain how nodE determines host r ange in the R, leguminosarum-legume symbiosis.