Nod gene-inducing flavonoids

Rao JR, JE Cooper (1994) Rhizobia catabolize nod gene-inducing flavonoids via C-ring fission mechanisms. J Bacterial 176 5409-5413. 

M. C. Bolanos-Vasquez and D. Werner, Effects of Rhizohium tropici, R. etii, and R. leguminosarum bv. phaseoU on nod gene-inducing flavonoids in root exudates of Phaseohis vulgaris. Molec. Plant Microbe Interact. 10 229 (1997). 

Hartwig, U.A. and Phillips D.A., Release and modification of nod-gene-inducing flavonoids from alfalfa seeds. Plant Physiol, 95, 804, 1991. 

Bolanos-Vasquez, M.C. and Werner, D., Effects of Rhizobium tropici, R. etli, and R. legumino-sarum bv. phaseoli on nod gene-inducing flavonoids in root exudates of Phaseolus vulgaris. Mol Plant-Microbe Interact., 10, 339, 1997. 

Hartwig, U. A., C. A. Maxwell, C. M. Joseph, and D. A. Phillips, Effects of alfalfa nod gene-inducing flavonoids on nodABC transcription in Rhizobium meliloti strains containing different nodD genes, J. Bacteriol., 172, 2793-2773 (1990a). 

According to Hungria and Stacey (31) more than 4000 flavonoids have been identified within the plant kingdom and some of them have been recognized as nod gene-inducers (Table 1). In addition, root flavonoids have been suggested as molecular signals for the initiation and development of mycorrhizal infection (Chaps. 7 and 9). 

Table 1 Some Flavonoids Inducing nod Gene Expression Isolated from Leguminose Hosts Under Sterile Conditions...

Figure 2 Structures of flavonoids present in root exudates of host plants and inducing nod gene expression in rhizobia (1) as 3,5,7,3 -tetrahydroxy-4 -methoxyflavanone, inducer in Rhizohium legiiminosarum bv. viciae (2) as 3, 4, 5, 7-tetrahydroxy-flavone, inducer in Rhizohium melilotr, (3) as 4, 7-dihydroxyisoflavone, inducer in Bradyrhizohium japonicum (4) as couinestrol, intermediate in phenylpropane metabolism, weak inducer. (From Ref. 64.)...

Maxwell, C.A. et al., A chalcone and two related flavonoids released from alfalfa roots induce nod genes of Rhizobium meliloti. Plant Physiol., 91, 842, 1989. 

Kape, R. et al., Isoliquiritigenin, a strong nod gene- and glyceollin resistance-inducing flavonoid from soybean root exudate, Appl Environ. Microbiol, 58, 1705, 1992. 

This rhamnan OPS is induced when the bacterium is cultured in the presence of flavonoids (molecules produced by die host legume that induce expression of die rhizobial nod genes) (Reuhs, et al., 2005), and a similar rhamnan was detected in bacteroids obtained from die host legume root nodule (Fraysse, et al., 2002, Jabbouri, et al., 1996). 

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