Abstract
Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.) and occurs when specific compounds, such as the flavone luteolin, are supplied by the host plant. Results reported here indicate how luteolin in the root and rhizosphere can affect subsequent N(2) fixation and plant growth. Previous experiments with ;Hairy Peruvian 32' (HP32), an alfalfa population produced from ;Hairy Peruvian' (HP) by two generations of selection for increased N(2) fixation and growth, found that HP32 had more root nodules and fixed more N(2) than the parental HP population. In the present study, flavonoid extracts of HP32 seedling roots are shown to contain a 60% higher concentration of compounds that induce transcription of a nodABC-lacZ fusion in R. meliloti than comparable extracts of HP roots. Chromatographic data indicated that HP32 roots had a 77% higher concentration of luteolin than HP roots. Adding 10 micromolar luteolin to the rhizosphere of HP seedlings increased nodulation, N(2) fixation, total N, and total dry weight but had no effect on nitrate assimilation. These data show that normal levels of flavone nodulation signals in the rhizosphere of HP alfalfa can limit root nodulation, symbiotic N(2) fixation, and seedling growth and suggest that one mechanism for increasing N(2) fixation can be the genetic enhancement of specific biochemical signals which induce nodulation genes in Rhizobium.
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Claims 7
Claim · model-written summary
Flavonoid extracts of HP32 alfalfa seedling roots contained a 60% higher concentration of compounds that induce nodABC transcription in Rhizobium meliloti than HP roots.
- Taxon
- alfalfa
Medicago sativae0 - Material
- HP32e1
- Interactor
- R. meliloti
Sinorhizobium melilotie1symbiont - Outcome
- concentration of compounds that induce transcription of a nodABC-lacZ fusione1
- Direction
- highere1
- Value
- 60%e1
- Comparator
- comparable extracts of HP rootse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“In the present study, flavonoid extracts of HP32 seedling roots are shown to contain a 60% higher concentration of compounds that induce transcription of a nodABC-lacZ fusion in R. meliloti than comparable extracts of HP roots”
Claim · model-written summary
HP32 alfalfa roots had a 77% higher concentration of luteolin than HP roots.
- Taxon
- alfalfaMedicago sativae0
- Material
- HP32e1
- Compound
- luteoline1
- Outcome
- concentration of luteoline1
- Direction
- highere1
- Value
- 77%e1
- Comparator
- HP rootse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“Chromatographic data indicated that HP32 roots had a 77% higher concentration of luteolin than HP roots”
Claim · model-written summary
Adding 10 micromolar luteolin to the rhizosphere of HP alfalfa seedlings increased nodulation, N(2) fixation and total N.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- Adding 10 micromolar luteolin to the rhizosphere of HP seedlingse1
- Outcome
- nodulation, N(2) fixation, total Ne1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“Adding 10 micromolar luteolin to the rhizosphere of HP seedlings increased nodulation, N(2) fixation, total N, and total dry weight but had no effect on nitrate assimilation”
Claim · model-written summary
Adding 10 micromolar luteolin to the rhizosphere of HP alfalfa seedlings increased total dry weight.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- Adding 10 micromolar luteolin to the rhizosphere of HP seedlingse1
- Outcome
- total dry weighte1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“Adding 10 micromolar luteolin to the rhizosphere of HP seedlings increased nodulation, N(2) fixation, total N, and total dry weight but had no effect on nitrate assimilation”
Claim · model-written summary
Adding 10 micromolar luteolin to the rhizosphere of HP alfalfa seedlings had no effect on nitrate assimilation.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- luteoline1
- Outcome
- nitrate assimilatione1
- Direction
- no effecte1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“Adding 10 micromolar luteolin to the rhizosphere of HP seedlings increased nodulation, N(2) fixation, total N, and total dry weight but had no effect on nitrate assimilation”
Claim · model-written summary
Normal levels of flavone nodulation signals may limit root nodulation in HP alfalfa.
- Taxon
- alfalfaMedicago sativae0
- Compound
- flavonee0
- Outcome
- root nodulatione0
- Direction
- limite0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These data show that normal levels of flavone nodulation signals in the rhizosphere of HP alfalfa can limit root nodulation, symbiotic N(2) fixation, and seedling growth”
Claim · model-written summary
Genetic enhancement of specific biochemical signals is proposed as one mechanism for increasing alfalfa N(2) fixation.
- Taxon
- alfalfaMedicago sativae0
- Outcome
- N(2) fixatione1
- Qualifier
- genetic enhancement of specific biochemical signalse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcription of the nodABC genes in Rhizobium meliloti is required for root nodule formation in alfalfa (Medicago sativa L.)”
e1“one mechanism for increasing N(2) fixation can be the genetic enhancement of specific biochemical signals which induce nodulation genes in Rhizobium”