Rhizobial purine and pyrimidine auxotrophs: nutrient supplementation, genetic analysis, and the symbiotic requirement for the novo purine biosynthesis

Noel, K. Dale; Diebold, Ronald J.; Cava, Joseph R.; Brink, Benita Anne

doi:10.1007/bf00446751

Cited by 51 publications

(52 citation statements)

References 25 publications

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“…It is unlikely that this negative result relates to the adenine auxotrophy we observed in pTZS+ Rhizobium strains (which we interpret as an indication that tzs expression depletes cytoplasmic pools of adenine andlor intermediates in the purine biosynthetic pathway). Nodule formation by Rhizobium purine auxotrophs is reportedly blocked early in development (Kerppola and Kahn, 1988;Noel et al, 1988), and we haveobserved that an R. melilotiadenine auxotroph (Rm2103) induced the formation of large ineffective nodules on alfalfa (J.B. Cooper, unpublished results). Although bean nodules elicited by purine auxotrophs lack infection threads, this effect was not specific for adenine, and purine auxotrophy had no effect on root hair curling (Noel et al, 1988).…”

Section: Discussionmentioning

confidence: 89%

Morphogenetic Rescue of Rhizobium meliloti Nodulation Mutants by trans-Zeatin Secretion

Cooper¹,

Long²

1994

The Plant Cell

108

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The development of nitrogen-fixing nodules is induced on the roots of legume host plants by Rhizobium bacteria. We employed a novel strategy to probe the underlying mechanism of nodule morphogenesis in alfalfa roots using pTZS, a broad host range plasmid carrying a constitutive trans-zeatin secretion (tzs) gene from Agrobacterium tumefaciens T37. This plasmid suppressed the Nod-phenotype of Rhizobium nodulation mutants such that mutants harboring pTZS stimulated the formation of nodulelike structures. Alfalfa roots formed more or fewer of these nodules according to both the nitrogen content of the environment and the position along the root at which the pTZS+ bacteria were applied, which parallels the physiological and developmental regulation of true Rhizobium nodule formation. This plasmid also conferred on Escherichia coli cells the ability to induce root cortical cell mitoses. Both the pattern of induced cell divisions and the spatially restricted expression of an alfalfa nodule-specific marker gene (MsENOD2) in pTZS-induced nodules support the conclusion that localized cytokinin production produces a phenocopy of nodule morphogenesis.

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Section: Discussionmentioning

confidence: 89%

Morphogenetic Rescue of Rhizobium meliloti Nodulation Mutants by trans-Zeatin Secretion

Cooper¹,

Long²

1994

The Plant Cell

108

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“…Purine auxotrophs of some rhizobia are defective in host invasion (29), but this is not the case with M. loti. 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR), a purine biosynthesis intermediate, was suggested to be a key compound promoting host invasion and nodule formation in mll5232 52 09T05d03 mlr1231 3 01T06e01 mll5942 16 29T01f09 mlr3298 61 36T02e02 mlr0937 15 23T04c04 mlr0237 37 a Information about each strain is the same as that described in the footnote to Table 1.…”

Section: Discussionmentioning

confidence: 99%

Identification of Mesorhizobium loti Genes Relevant to Symbiosis by Using Signature-Tagged Mutants

et al. 2011

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Signature-tagged mutagenesis was applied to Mesorhizobium loti, a nitrogen-fixing root-nodule symbiont of the leguminous plant Lotus japonicus. We arranged 1,887 non-redundant mutant strains of M. loti into 75 sets, each consisting of 24 to 26 strains with a different tag in each strain. These sets were each inoculated en masse onto L. japonicus plants. Comparative analysis of total DNA extracted from inoculants and resulting nodules based on quantitative PCR led to the selection of 69 strains as being reduced in relative abundance during nodulation. Plant assays conducted with individual strains confirmed that 3 were defective in nodulation (Nod − ) and that 10 were Nod + but defective in nitrogen fixation (Fix − ); in each case, the symbiosis deficiency could be attributed to the transposon insertion carried by that strain. Although the remaining 56 strains were Fix + , 33 of them showed significantly reduced competitiveness during nodulation. Among the mutants we identified are known genes that are diverse in predicted function as well as some genes of unknown function, which demonstrates the validity of this screening procedure for functional genomics in rhizobia.Key words: Mesorhizobium loti, signature-tagged mutagenesis, symbiosis, competitiveness, root nodule Rhizobia are a group of soil bacteria that establish a nitrogen-fixing symbiosis with leguminous plants. Mesorhizobium loti is an α-proteobacterial species of the group and a symbiotic partner of Lotus japonicus; this symbiotic pair is a well-documented model system for molecular genetic studies (20, 31). Some rhizobia, including M. loti, elicit root-hair curling and nodule organogenesis on roots of host plants at an early step during symbiosis. Such plant responses are triggered specifically by signaling compounds, called Nod factors, produced by compatible rhizobia. Rhizobia colonize curled root hairs and invade developing nodules via infection threads, which are formed by invagination of the root-hair cell membrane. The rhizobia are then released into the host nodule cells (33,42). These intracellular bacteria (bacteroids) reduce dinitrogen into ammonia by use of a carbon and energy source originating from photosynthates. Host plants are supplied with the fixed nitrogen and thus are able to grow under nitrogen-poor conditions. In a free-living state, rhizobia can metabolize a wide range of carbon and nitrogen sources. This metabolic versatility allows rhizobia to adapt to the nutritional complexity of the rhizosphere, which is affected by plant root exudates (14,15,25,36).Whole genome sequences have been determined for several rhizobial species; their genomes range in size from 5.4 Mb (Azorhizobium caulinodans), 6.7 Mb (Sinorhizobium meliloti) and 7.6 Mb (M. loti) to 8.5 Mb (Bradyrhizobium sp. BTAi1) and 9.1 Mb (Bradyrhizobium japonicum) (8,10,16,17,22). These large sizes can be explained by the need to accommodate the many genes responsible for symbiotic capacity and metabolic versatility. A number of genes have been assigned to functions require...

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“…Mutants of B. japonicum requiring glutamine or glutamate as a nitrogen source showed similar differences in enzymes, slightly lower glutamine synthetase (GS), 3-5 times lower glutamate synthase but more than 10 times higher alanine dehydrogenase (ADH) activity 81 . According to Noel et al (1988) 38 , undiminished metabolic fl ow through de novo purine biosynthesis or a particular intermediate in the pathway is essential in early symbiotic interaction. Mutants in ornithine transcarbamylase, argininosuccinate synthetase or serine glycine biosynthesis isolated by Kerppola and Kahn 85 from S. meliloti 104A14 formed nitrogen fi xing (Fix + ) nodules on the roots of alfalfa (Medicago sativa).…”

Section: Biochemical and Enzymatic Studies With Auxotrophic Mutantsmentioning

confidence: 99%

Auxotrophy in rhizobia revisited

Yadav

2007

Indian J Microbiol

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Among the various types of mutations studied in rhizobia, the auxotrophic mutations (which confer on the mutants the inability to synthesize certain essential substances such as amino acids, vitamins and nucleic acids), are the most favoured ones as these can be used as suitable markers for genetic analysis. An important property of rhizobia is their effectiveness i.e. their ability to fi x atmospheric nitrogen into ammonia within the nodule. Special interest in this category of mutations by rhizobial geneticists is due to the fact that there is a strong correlation between the metabolic defects and the ineffectiveness (Nod -and/or Fix -) of the rhizobial strains. Auxotrophic mutants of various species of rhizobia with defects in the synthesis of nucleic bases, vitamins and amino acids have been obtained by mutagenising with physical, chemical and Tn5 mutagens. These mutants have been used in mapping studies as well as in establishing a correlation between its metabolic requirement and symbiotic relationship with the host plant. The present review deals with the isolation of auxotrophs, and their genetic, biochemical and symbiotic characterization. The review also encompasses the studies on the elucidation of biosynthetic pathways of nutritional substances in rhizobia.

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Rhizobial purine and pyrimidine auxotrophs: nutrient supplementation, genetic analysis, and the symbiotic requirement for the novo purine biosynthesis

Cited by 51 publications

References 25 publications

Morphogenetic Rescue of Rhizobium meliloti Nodulation Mutants by trans-Zeatin Secretion

Morphogenetic Rescue of Rhizobium meliloti Nodulation Mutants by trans-Zeatin Secretion

Identification of Mesorhizobium loti Genes Relevant to Symbiosis by Using Signature-Tagged Mutants

Auxotrophy in rhizobia revisited

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