Growth temperature regulation of host-specific modifications of rhizobial lipo-chitin oligosaccharides::: the function of nodX is temperature regulated

Lipo-chitin oligosaecharides (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 by. viciae Al 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 by. 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 by. 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.Microbial Biotechnolog

Phospholipids of Rhizobium contain nodE-determined highly unsaturated fatty acid moieties

Microbial Biotechnolog

Increased uptake of putrescine in the Rhizosphere inhibits competitive root colonization by Pseudomonas fluoresecens strain WCS365

Microbial Biotechnolog

NodFE-dependent fatty acids that lack an α-β unsaturation are subject to differential transfer, leading to novel phospholipids

Microbial Biotechnolog

Introduction of the phzH gene of Pseudomonas chlororaphis PCL1391 extends the range of biocontrol ability of Phenazine-1-Carboxylic Acid-Producing pseudomonas spp. strains

Microbial Biotechnolog

The production of species-specific highly unsaturated fatty acyl-containing LCOs from Rhizobium leguminosarum bv. trifolii is stringently regulated by nodD and involves the nodRL genes

Microbial Biotechnolog

Novel branched Nod factor structure results from a-(1-3) fucosyl transferase activity: the major lipo-chitin oligosaccharides from Mesorhizobium loti strain NZP2213 bear an a-(1-3) fucosyl substituent on a nonterminal backbone residue

Microbial Biotechnolog

Rhizobium leguminosarum bv. trifolii produces Lipo-chitin oligosaccharides with nodE-dependent highly unsaturated fatty acyl moieties. An electrospray ionization and collision-induced dissociation tandem mass spectrometric study

Microbial Biotechnolog

Host specificity of Rhizobium leguminosarum is determined by the hydrophobicity of highly unsaturated fatty acyl moieties of the nodulation factors

The nodE genes of Rhizobium leguminosarum bvs, trifolii and viciae strains are the major determinants of the host range of nodulation, Using mass spectrometry we have analyzed the structures of the major and minor lipooligosaccharides produced by two R, leguminosarum strains that differ only in the origin of the nod genes, The strain containing the nod genes of R. l. by. viciae produces lipo-chitin oligosaccharide (LCO) molecules that contain the common cis-vaccenyl (C18:1) or a highly unsaturated acyl (C18:4) group that is determined by nodE (Spaink et al, Nature 354:125-130, 1991), Here we show that, in addition, minor quantities of analogous molecules that contain different common fatty acyl groups such as stearyl (C18:0), palmityl (C16:0), and palmitoyl (C16:1) groups are produced, The set of LCOs produced by the strain containing the R. l. by. trifolii nod genes is similar, but major differences are found in the length and unsaturation of the fatty acyl groups of various LCOs. The R. l, by. trifolii strain does not produce LCO molecules that contain the C18:4 fatty acyl group. Instead, a complex mixture of other unsaturated fatty acyl groups containing either two, three, or four double bonds is produced, These novel fatty acyl groups are more hydrophobic than the C18:4 fatty acyl group found in by. viciae, as judged by highperformance liquid chromatography retention times, probably as a result of the longer carbon chain length, the lack of a cis double bond, or both, Another difference is that the relative amount of highly unsaturated fatty acid-containing LCOs produced by R. l. by. trifolii is much smaller An isogenic R. l. by. trifolii strain containing a Tn5 insertion in the nodE gene only produces LCOs containing the common fatty acyl groups and not the highly unsaturated types, The results indicate that the difference in the host range of the R. l. bvs, viciae and trifolii is determined by the overall hydrophobicity of the highly unsaturated fatty acyl moieties of LCOs rather than by a specific structural feature.Microbial Biotechnolog

Comparison of characteristics of the nodX genes from various Rhizobium leguminosarum strains

Microbial Biotechnolog