Rhizobium nod gene inducers exuded naturally from roots of common bean (Phaseolus vulgaris L.)

Cuatro compuestos exudados de raices jovenes de frijol negro cv. PI165426CS inducen la transcripcion de genes nod en Rhizobium leguminosarum bv. phaseoli. Se identificaron los 3 inductores de genes nod mas activos mediante metodos espectroscopicos (absorbencia visible/ultravioleta, resonancia magnetica nuclear de protones y espectrometria de masas) como eriodictiol (5,7,3 prima,4 prima-tetrahidroxiflavanona), naringenina (5,7,4 prima- trihidroxiflavanona) y 7-O-glicosido de genisteina (5,7,4 prima- trihidroxiisoflavona). Comparaciones con las normas autenticas verificaron las estructuras quimicas de los aglicones y su capacidad para inducir actividad de beta-galactosidasa en cepas de R. leguminosarum que contenian fusiones nodA-lacZ o nodC-lacZ controladas por los genes nodD de R. leguminosarum bv. phaseoli. Las raices de plantulas de 9 dias de edad liberaron 42, 281 y 337 nanomoles/planta/dia de genisteina, eriodictiol y naringenina, resp. La genisteina y la naringenina indujeron la mayor actividad de beta-galactosidasa y requirieron concn. inferiores para la induccion media-max. que el eriodictiol. La comparacion de la actividad inductora de genes nod de enjuagues de semillas con el exudado de raices de frijol cv. PI165426CS mostro que los flavonoides de la raiz se liberaron aprox. 6 por ciento la tasa de los de las semillas en base molar, pero en prom. los compuestos individuales de las raices fueron aprox. 3 veces mas activos que los inductores de los genes nod de las semillas. (RA-CIAT) spa

Four compounds exuded from young roots of a black-seeded bean (Phaseolus vulgaris L., cv. PI165426CS) induce transcription of nod genes in Rhizobium leguminosarum biovar phaseoli. The three most active nod gene inducers were identified by spectroscopic methods (ultraviolet/visible absorbance, proton nuclear magnetic resonance, and mass spectrometry) as being eriodictyol (5,7,3 prime,4 prime- tetrahydroxyflavanone), naringenin (5,7,4 prime- trihydroxyflavanone), and a 7-O-glycoside of genistein (5,7,4 prime- trihydroxyisoflavone). Comparisons with authentic standards verified the chemical structures of the aglycones and their capacity to induce beta-galactosidase activity in R. leguminosarum strains containing nodA-lacZ or nodC-lacZ fusions controlled by R. leguminosarum biovar phaseoli nodD genes. Roots of 9-day-old seedlings released 42, 281, and 337 nanomoles per plant per day of genistein, eriodictyol, and naringenin, respectively. Genistein and naringenin induced higher maximum beta-galactosidase activities and required lower concentrations for half-maximum induction than eriodictyol. Comparing the nod gene-inducing activity of seed rinses with root exudate from PI165426CS bean showed that root flavonoids were released at about 6 percent the rate of those from seeds on a molar basis, but on average the individual compounds from roots were approximately three times more active than nod gene inducers from seeds. (AS) eng