Abstract
Background. Alfalfa root nodule bacteria (Sinorhizobium meliloti) are among the most active symbiotic N2-fixers. Their symbiotic efficiency (SE) defined as an ability to enhance the productivity of inoculated host plants is the polygenic trait controlled by a complicated system of genes, inactivation of which can result in either decrease or increase of SE. Analysis of previously identified eff-genes, whose mutations result in SE increase, revealed their location in different parts of genome (chromosome or megaplasmids) and demonstrated that these genes are not involved in operation of nitrogenase system. Mutations in these genes have pleiotropic effects, changing various cultural-biochemical properties of bacteria. Materials and methods. The object of research were the laboratory S. meliloti strain CXM1-105 and its Tn5-mutants with Eff++ phenotype, which are able to grow in diagnostic media containing indicator of cell redox potential ТТC, herbicide 2М-4ХМ or the Congo Red dye. New eff-genes were identified using the modified method of “inverted” PCR. Results. We obtained three Tn5 mutants with an increased SE in which the symbiotic phenotypes are dependent on the host. Two-factor analysis of variance demonstrated that the genotypic difference between mutants is most pronounced under the salt stress, while in its absence SE is determined mostly by the host genotype. Molecular-biological analysis revealed that the T4 mutant harbours the Tn5 insertion in the mtaD gene, T795 - in the thiC gene, and M3 - in the gene which encodes a protein belonging to the GntR family of transcription regulators. Conclusion. We demonstrated firstly that mutations in genes involved in transcription regulation, phosphonate metabolism and thiamine biosynthesis may result in a SE increase. The “inverted” PCR method enabled us to rapidly extract DNA fragments flanking the transposon, which suggests applicability of this method for identification of new rhizobia genes marked by Tn5.
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Claims 8
Claim · model-written summary
Three S. meliloti Tn5 mutants with increased symbiotic efficiency were obtained, and their symbiotic phenotypes depend on the host.
- Taxon
- sinorhizobium meliloti
Sinorhizobium melilotit0 - Interactor
- alfalfa
Medicago sativat0host - Outcome
- three Tn5 mutants with an increased SEe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“We obtained three Tn5 mutants with an increased SE in which the symbiotic phenotypes are dependent on the host”
Claim · model-written summary
In a two-factor analysis of variance, the genotypic difference between the S. meliloti mutants was most pronounced under salt stress.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Treatment
- salt stresse0
- Interactor
- alfalfaMedicago sativat0host
- Outcome
- genotypic difference between mutants is most pronouncede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“the genotypic difference between mutants is most pronounced under the salt stress”
Claim · model-written summary
Without salt stress, symbiotic efficiency was determined mostly by the host genotype.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Interactor
- alfalfaMedicago sativat0host
- Outcome
- SE is determined mostly by the host genotypee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“in its absence SE is determined mostly by the host genotype”
Claim · model-written summary
The T4 mutant carries the Tn5 insertion in the mtaD gene.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Material
- T4 mutante0
- Interactor
- alfalfaMedicago sativat0host
- Gene
- mtaDe0
- Outcome
- Tn5 insertion in the mtaD genee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“the T4 mutant harbours the Tn5 insertion in the mtaD gene”
Claim · model-written summary
The T795 mutant carries the Tn5 insertion in the thiC gene.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Material
- T795e0
- Interactor
- alfalfaMedicago sativat0host
- Gene
- thiCe0
- Outcome
- in the thiC genee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“T795 - in the thiC gene”
Claim · model-written summary
The M3 mutant carries the Tn5 insertion in a gene encoding a protein of the GntR family of transcription regulators.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Material
- M3e0
- Interactor
- alfalfaMedicago sativat0host
- Gene
- GntR family of transcription regulatorse0
- Outcome
- in the gene which encodes a protein belonging to the GntR family of transcription regulatorse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“M3 - in the gene which encodes a protein belonging to the GntR family of transcription regulators”
Claim · model-written summary
The authors conclude that mutations in genes for transcription regulation, phosphonate metabolism and thiamine biosynthesis may increase symbiotic efficiency.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Interactor
- alfalfaMedicago sativat0host
- Gene
- genes involved in transcription regulation, phosphonate metabolism and thiamine biosynthesise0
- Outcome
- SE increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“mutations in genes involved in transcription regulation, phosphonate metabolism and thiamine biosynthesis may result in a SE increase”
Claim · model-written summary
The inverted PCR method allowed rapid extraction of DNA fragments flanking the Tn5 transposon, suggesting it can be used to identify new rhizobial genes marked by Tn5.
- Taxon
- sinorhizobium melilotiSinorhizobium melilotit0
- Interactor
- alfalfaMedicago sativat0host
- Outcome
- rapidly extract DNA fragments flanking the transposone0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“nodule bacteria sinorhizobium meliloti involved in the control of efficiency of symbiosis with alfalfa”
e0“The “inverted” PCR method enabled us to rapidly extract DNA fragments flanking the transposon”