Inoculation of Vicia sativa subsp. nigra roots with Rhizobium leguminosarum biovar viciae results in release of nod gene activating flavanones and chalcones

Abstract

Flavonoids released by roots of Vicia sativa subsp. nigra (V. sativa) activate nodulation genes of the homologous bacterium Rhizobium leguminosarum biovar viciae (R. l. viciae). Inoculation of V. sativa roots with infective R. l. viciae bacteria largely increases the nod gene-inducing ability of V. sativa root exudate (A.A.N. van Brussel et al., J Bact 172: 5394-5401). The present study showed that, in contrast to sterile roots and roots inoculated with R. l. viciae cured of its Sym plasmid, roots inoculated with R. l. viciae harboring its Sym plasmid released additional nod gene-inducing flavonoids. Using 1H-NMR, the structures of the major inducers released by inoculated roots, 6 flavanones and 2 chalcones, were elucidated. Roots extracts of (un)inoculated V. sativa contain 4 major non-inducing, most likely glycosylated, flavonoids. Therefore, the released flavonoids may either derive from the root flavonoids or inoculation with R. l. viciae activates de novo flavonoid biosynthesis.

Induction of Microbial Genes for Pathogenesis and Symbiosis by Chemicals from Root Border Cells

“…of signals that stimulate increased levels of extracellular nod gene-inducing signals from plant roots in a phenomenon described as the ini response (van Brussel et al, 1990). The ini response is correlated with an increased expression of flavonoid biosynthetic genes in specific root tissues (McKhann et al, 1997) and may occur in response to specific signals from nod genes (van Brussel et al, 1990;Recourt et al, 1991). Our results reveal that detached border cells, in the absence of exogenous nutrients, constitute one defined cell type that can respond to signals from rhizobia by an increase in extracellular chemicals that stimulate nod gene induction.…”

“…4), suggesting that a threshold concentration of border cells may be required for the production and/or release of nod geneinducing chemicals. production of nod gene-activating flavanones and chalcones (van Brussel et al, 1990;Recourt et al, 1991), and this response is correlated with the induction of plant genes required for their production (McKhann et al, 1997). To determine whether border cells exhibit a similar response to R. leguminosarum bv viciae, border cells were incubated for 12 h with or without bacteria.…”

Anthocyanidins and Flavonols, Major nod Gene Inducers from Seeds of a Black-Seeded Common Bean (Phaseolus vulgaris L.)

“…2). The presence of so many structurally different nodgene-inducing flavonoids in the seed rinse differs markedly from exudates of other legumes that have been studied in the absence of rhizobial symbionts (8,13,18,29,31,32).…”

“…japonicum (18,33), R. leguminosarum bv3 viceae (8,31,40), R. leguminosarum bv trifolii (32), and the broad-host-range Rhizobium NGR234 (2). Some commercially available flavonoids induce nod genes in R. leguminosarum bv phaseoli (4), but no naturally occurring nod inducers have been reported from common bean.…”

Importance des composés phénoliques dans les interactions entre plantes et microorganismes: exemple des relationsRhizobium/légumineuses

“…De plus, Jes flavonoi"des liberes par des plantes de soja ou de vesce inoculees avec des souches de Rhizobium compatibles se sont reveles quantitativement et qualitativement differents des flavono"ides detectes dans Jes exsudats des pi antes non inoculees (Recourt et al, 1991 ;Van Brussel et al, 1990;Schmidt et a!., 1994 ). Ces nouveaux flavono"ides pourraient avoir pour origine le pool des flavonoldes glycosyles naturellement exsudes par Ia racine ou etre issus de nouvelles biosyntheses declenchees par !…”