Abstract
Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean. Mutations that cause this symbiotic defect mapped to seven partially-sequenced purine biosynthetic genes, all responsible for steps before the production of the intermediate 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). Supplementing the root medium with AICA riboside, the unphosphorylated form of AICAR, substantially enhanced nodule development. Of the purines tested, only inosine enhanced nodulation, but very high concentrations were required for this effect. Studies with a double mutant indicated that the histidine pathway was required for inosine's effect, presumably because AICAR is produced as a byproduct of histidine synthesis. AICA riboside also promoted infection of soybean by two R. fredii purine auxotrophs, even though these mutants grew poorly with AICA riboside as a purine source. Nodules elicited by purine auxotrophs in the presence of AICA riboside had infection threads and anatomical features characteristic of normal nodules. The nodule-specific proteins, leghemoglobin and uricase, were detected in these nodules, although at lower levels than in nodules elicited by the wild type. Analysis of the temporal requirement for AICA riboside indicated that it was required during the entire infection process, rather than just for infection thread initiation. These studies also suggested that a critical stage of infection is reached six days post-inoculation, at which development becomes committed to forming a true root nodule structure. To better understand how AICA riboside enhances nodule development, AICA riboside utilization and uptake were examined and compared in three Rhizobium genetic backgrounds. A mutant resistant to the toxic AICA riboside analog, pyrazofurin, could not convert AICA riboside to AICAR. Nodulation assays with a purine auxotrophic derivative of this mutant demonstrated that this conversion was required for AICA riboside to promote infection. These results support the hypothesis that rhizobia divert AICAR from purine biosynthesis for the production of a factor that induces infection thread development in the plant. Successful infection by rhizobia triggers the nodule-specific developmental pathway, which leads to the formation of a true nodule structure that is distinct from the root-like structure that develops in the absence of infection.
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Claims 15
Claim · model-written summary
Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean.
- Taxon
- beane1
- Material
- Purine auxotrophse1
- Interactor
- Rhizobium leguminosarum CFN42
Rhizobium leguminosarume1symbiont - Outcome
- uninfected pseudonodulese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
Claim · model-written summary
Symbiotic-defect mutations mapped to seven partially-sequenced purine biosynthetic genes, all acting before AICAR production.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Mutations that cause this symbiotic defect mapped to seven partially-sequenced purine biosynthetic genes”
Claim · model-written summary
Supplementing the root medium with AICA riboside substantially enhanced nodule development on bean.
- Taxon
- beane1
- Treatment
- Supplementing the root medium with AICA ribosidee2
- Outcome
- nodule developmente2
- Direction
- enhancede2
- Qualifier
- substantiallye2
Not reportedComparator
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Supplementing the root medium with AICA riboside, the unphosphorylated form of AICAR, substantially enhanced nodule development”
Claim · model-written summary
Of the purines tested, only inosine enhanced nodulation, and very high concentrations were required.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Of the purines tested, only inosine enhanced nodulation, but very high concentrations were required for this effect”
Claim · model-written summary
The histidine pathway was required for the effect of inosine, presumably because AICAR is a byproduct of histidine synthesis.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Studies with a double mutant indicated that the histidine pathway was required for inosine's effect, presumably because AICAR is produced as a byproduct of histidine synthesis”
Claim · model-written summary
AICA riboside promoted infection of soybean by two R. fredii purine auxotrophs.
- Taxon
- soybean
Glycine maxe1 - Treatment
- AICA ribosidee1
- Interactor
- R. fredii purine auxotrophs
.JPG?width=60)
Sinorhizobium frediie1symbiont - Outcome
- infectione1
- Direction
- promotede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.JPG?width=500)
Verbatim
e1“AICA riboside also promoted infection of soybean by two R. fredii purine auxotrophs, even though these mutants grew poorly with AICA riboside as a purine source”
Claim · model-written summary
The R. fredii purine auxotrophs grew poorly on AICA riboside as a purine source on soybean.
- Taxon
- soybeanGlycine maxe1
- Interactor
- R. fredii purine auxotrophsSinorhizobium frediie1symbiont
- Outcome
- grew poorlye1
- Qualifier
- with AICA riboside as a purine sourcee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“AICA riboside also promoted infection of soybean by two R. fredii purine auxotrophs, even though these mutants grew poorly with AICA riboside as a purine source”
Claim · model-written summary
Nodules elicited by purine auxotrophs with AICA riboside had infection threads and anatomical features characteristic of normal nodules.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Nodules elicited by purine auxotrophs in the presence of AICA riboside had infection threads and anatomical features characteristic of normal nodules”
Claim · model-written summary
Leghemoglobin and uricase were detected in nodules at lower levels than in wild-type nodules.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“The nodule-specific proteins, leghemoglobin and uricase, were detected in these nodules, although at lower levels than in nodules elicited by the wild type”
Claim · model-written summary
AICA riboside was required during the entire infection process, not just for infection thread initiation.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Analysis of the temporal requirement for AICA riboside indicated that it was required during the entire infection process, rather than just for infection thread initiation”
Claim · model-written summary
A critical stage of infection is reached six days post-inoculation, when development becomes committed to a true root nodule structure.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“a critical stage of infection is reached six days post-inoculation, at which development becomes committed to forming a true root nodule structure”
Claim · model-written summary
The AICA riboside-resistant mutant could not convert AICA riboside to AICAR.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“A mutant resistant to the toxic AICA riboside analog, pyrazofurin, could not convert AICA riboside to AICAR”
Claim · model-written summary
In nodulation assays, conversion of AICA riboside to AICAR was required for AICA riboside to promote infection.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Nodulation assays with a purine auxotrophic derivative of this mutant demonstrated that this conversion was required for AICA riboside to promote infection”
Claim · model-written summary
Rhizobia divert AICAR from purine biosynthesis to produce a factor that induces infection thread development in the plant.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“These results support the hypothesis that rhizobia divert AICAR from purine biosynthesis for the production of a factor that induces infection thread development in the plant”
Claim · model-written summary
Successful infection by rhizobia triggers the nodule-specific developmental pathway that forms a true nodule structure distinct from the root-like structure.
Verbatim
e1“Purine auxotrophs of Rhizobium leguminosarum CFN42 elicit uninfected pseudonodules on bean”
e2“Successful infection by rhizobia triggers the nodule-specific developmental pathway, which leads to the formation of a true nodule structure that is distinct from the root-like structure”
The same questions in other papers
in vitro · symbiosis · Phaseolus vulgaris (common bean)Positive and negative results
2 papers in the same direction as this paper · 2 in the opposite direction
- negative
- negative
- positive
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