Rhizobium nodulation genes

Recently, a new polyketide biosynthetic pathway in bacteria that parallels the well studied plant PKSs has been discovered that can assemble small aromatic metabolites.8,9 These type III PKSs10 are members of the chalcone synthase (CHS) and stilbene synthase (STS) family of PKSs previously thought to be restricted to plants.11 The best studied type III PKS is CHS. Physiologically, CHS catalyzes the biosynthesis of 4,2, 4, 6 -tetrahydroxychalcone (chalcone). Moreover, in some organisms CHS works in concert with chalcone reductase (CHR) to produce 4,2 ,4 -trihydroxychalcone (deoxychalcone) (Fig. 12.1). Both natural products constitute plant secondary metabolites that are used as precursors for the biosynthesis of anthocyanin pigments, anti-microbial phytoalexins, and chemical inducers of Rhizobium nodulation genes.12... 

Spaink, H.P. et al., Rhizobium nodulation gene nodD as a determinant of host specificity, Nature, 328, 337, 1987. 

A. Nodulation genes—production of nod factors Flavonoids Rhizobium spp. 90,91.92... 

B. G. Rolfe, Flavones induce expression of nodulation genes in Rhizobium, Nature 323 632 (1986). 

B. D. H. Jarvis, L. J. H. Ward, and E. A. Slade, Expression by soil bacteria of nodulation genes from Rhizobium leguminosarum biovar trifolii. Appl. Environ. Microbiol. 55 1426-1434 (1989). 

Maxwell, C.A. et al., Molecular characterization and expression of isoliquiritigenin 2 -0-methyltransferase, an enzyme specifically involved in the biosynthesis of an inducer of Rhizobium meliloti nodulation genes. Plant J., 4, 971, 1993. 

Peters, N.K., Frost, J.W., and Long, S.R., A plant flavone, luteolin, induces expression of Rhizobium meliloti nodulation genes, Science, 233, 917, 1986. 

Firmin, J.L. et al., Flavonoid activation of nodulation genes in Rhizobium reversed by other compounds present in plants. Nature, 324, 90, 1986. 

Caetano-Anolles, G., Christ-Estes, D.K., and Bauer, W.D., Chemotaxis of Rhizobium meliloti to the plant flavone luteolin requires functional nodulation genes, J. Bacteriol, 170, 3164, 1988. 

Horvath B., Bachem, C.W.B., Schell, J. Kondorosi, A. (1987). Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal interacting with the nodD gene product. The EM BO Journal 6, 841-8. 

Kondorosi, A. (1991). Regulation of nodulation genes in Rhizobium. In Molecular Signals in Plant-Microbe Communication, ed. D.P.S. Verma pp. 325-40. Boca Raton, FL CRC Press. 

Apigenin (70b), luteolin (70c) and related polyhydroxyflavones can activate the nodulation genes of the nitrogen-fixation bacteria (genus Rhizobium) in the leguminous plants such as peas. This is the first time that simple flavonoids have been shown to be involved in gene regulation [367-369]. 

The formation of root nodules associated with nitrogen fixation in legumes is an area of active study. Hormonal involvement in the developmental modifications needed to establish the nodule, has been reviewed [186]. Studies on the molecular characterization of nodulation have shown that early nodulation genes are induced by auxin transport inhibitors, and inhibitor treated roots produce pseudonodules [187]. Rhizobium species appear to produce lAA by a pathway involving the conversion of tryptophan to indole-... 

Ferret, X., Staehelin, C., William, J.B. (2000) Molecular basis of symbiotic promiscuity. Microbiol Mol Biol R. 64, 180-201 Persson, J. and Nasholm, T. (2001) Amino acid uptake a widespread ability among boreal forest plants. Ecol Lett. 4,434-438 Peters, N.K., Frost, J.W. and Long, S.R. (1986) A plant flavone, luteolin, induces expression of Rhizobium meliloti nodulation genes. Science 233,977-980... 

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