Abstract
Root exudates of alfalfa (Medicago sativa L.) inoculated with symbiotic Rhizobium meliloti bacteria contained three isoflavonoids that were not found in exudates of uninoculated plants. Data from proton nuclear magnetic resonance, mass spectrometry, and ultraviolet-visible absorbance analyses indicated that root exudates of inoculated plants contained aglycone and glycoside forms of the phytoalexin medicarpin and a formononetin-7-O-(6"-O-malonylglycoside), a conjugated form of the medicarpin precursor formononetin. The medicarpin molecules did not induce nod gene transcription in R. meliloti, but the formononetin-7-O-(6"-O-malonylglycoside) induced nod genes regulated by both NodD1 and NodD2 proteins in R. meliloti. Hydrolysis of either the malonyl or the glycosyl linkage from the formononetin conjugate eliminated nod gene-inducing activity. The nod gene-inducing activity of crude root exudates was increased 200 and 65% upon inoculation with R. meliloti or R. leguminosarum bv phaseoli, respectively. When root exudate from uninoculated alfalfa was incubated with R. meliloti, high performance liquid chromatography analyses showed no evidence that bacterial metabolism produced medicarpin. These results indicate that alfalfa responds to symbiotic R. meliloti by exuding a phytoalexin normally elicited by pathogens and that the microsymbiont can use a precursor of the phytoalexin as a signal for inducing symbiotic nod genes.
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Claims 8
Claim · model-written summary
Rhizobium meliloti inoculation was associated with three isoflavonoids absent from uninoculated alfalfa root exudates.
- Taxon
- alfalfa (Medicago sativa L.)
Medicago sativae0 - Treatment
- inoculated with symbiotic Rhizobium meliloti bacteriae0
- Interactor
- Rhizobium meliloti
Sinorhizobium melilotie0symbiont - Outcome
- three isoflavonoidse0
- Direction
- not founde0
- Comparator
- uninoculated plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root exudates of alfalfa (Medicago sativa L.) inoculated with symbiotic Rhizobium meliloti bacteria contained three isoflavonoids that were not found in exudates of uninoculated plants.”
Claim · model-written summary
Inoculated alfalfa root exudates contained medicarpin and a formononetin conjugate.
- Taxon
- AlfalfaMedicago sativat0
- Outcome
- aglycone and glycoside forms of the phytoalexin medicarpin and a formononetin-7-O-(6"-O-malonylglycoside)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root exudates of inoculated plants contained aglycone and glycoside forms of the phytoalexin medicarpin and a formononetin-7-O-(6"-O-malonylglycoside)”
t0“Alfalfa”
Claim · model-written summary
Medicarpin did not induce R. meliloti nod gene transcription.
- Taxon
- AlfalfaMedicago sativat0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Compound
- medicarpine0
- Outcome
- nod gene transcriptione0
- Direction
- did not inducee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The medicarpin molecules did not induce nod gene transcription in R. meliloti”
t0“Alfalfa”
Claim · model-written summary
The formononetin conjugate induced nod genes regulated by NodD1 and NodD2 in R. meliloti.
- Taxon
- AlfalfaMedicago sativat0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Gene
- NodD1 and NodD2 proteinse0
- Compound
- formononetin-7-O-(6"-O-malonylglycoside)e0
- Outcome
- nod genese0
- Direction
- inducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the formononetin-7-O-(6"-O-malonylglycoside) induced nod genes regulated by both NodD1 and NodD2 proteins in R. meliloti”
t0“Alfalfa”
Claim · model-written summary
Hydrolysis of either linkage eliminated nod gene inducing activity of the formononetin conjugate.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- Hydrolysis of either the malonyl or the glycosyl linkagee0
- Compound
- formononetin conjugatee0
- Outcome
- nod gene-inducing activitye0
- Direction
- eliminatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hydrolysis of either the malonyl or the glycosyl linkage from the formononetin conjugate eliminated nod gene-inducing activity.”
t0“Alfalfa”
Claim · model-written summary
R. meliloti inoculation increased nod gene inducing activity of crude alfalfa root exudates by 200%.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- inoculation with R. melilotie0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Outcome
- nod gene-inducing activity of crude root exudatese0
- Direction
- increasede0
- Value
- 200e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nod gene-inducing activity of crude root exudates was increased 200 and 65% upon inoculation with R. meliloti or R. leguminosarum bv phaseoli, respectively.”
t0“Alfalfa”
Claim · model-written summary
R. leguminosarum bv phaseoli inoculation increased nod gene inducing activity of alfalfa exudates by 65%.
- Taxon
- AlfalfaMedicago sativat0
- Treatment
- R. leguminosarum bv phaseolie0
- Interactor
- R. leguminosarum bv phaseoli
Rhizobium leguminosarume0symbiont - Outcome
- nod gene-inducing activity of crude root exudatese0
- Direction
- increasede0
- Value
- 65%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The nod gene-inducing activity of crude root exudates was increased 200 and 65% upon inoculation with R. meliloti or R. leguminosarum bv phaseoli, respectively.”
t0“Alfalfa”
Claim · model-written summary
Incubating uninoculated alfalfa exudate with R. meliloti produced no evidence of bacterial medicarpin production.
- Taxon
- AlfalfaMedicago sativat0
- Interactor
- R. melilotiSinorhizobium melilotie0symbiont
- Outcome
- no evidence that bacterial metabolism produced medicarpine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When root exudate from uninoculated alfalfa was incubated with R. meliloti, high performance liquid chromatography analyses showed no evidence that bacterial metabolism produced medicarpin.”
t0“Alfalfa”
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