Physiological Evidence for Novel Tryptophan-Dependent Pathway for Indole Acetic Acid Synthesis in Azospirillum brasilense

Carreño-López, Ricardo; Campos-Reales, N.; Alavez-Junco, L. G.; Elmerich, Claudine; Baca, Beatriz E.

doi:10.1007/0-306-47615-0_240

Cited by 3 publications

(8 citation statements)

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“…Production of detectable quantities of IAA usually requires an exogenous source of tryptophan which, in the rhizosphere, is present in host root exudates (13,14,27,43,44,45,64,72,73). The addition of tryptophan to culture media induced ipdC expression in E. cloacae UW5 and in A. brasilense strain Sp7 (44,53,73), although the regulatory proteins that control tryptophan-mediated ipdC expression were not identified in these studies.…”

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confidence: 80%

“…Several studies have shown that environmental signals present in the rhizosphere increase bacterial IAA production; however, the mechanisms by which these signals are transduced in bacteria are not well understood. In many PGPR, IAA is synthesized only when tryptophan is supplied in the culture medium (13,14,43,44,64,73). This may be due to increased availability of the biosynthetic precursor tryptophan and/or to a requirement for tryptophan for induction of the genes in the IAA biosynthetic pathway.…”

Section: Vol 190 2008mentioning

confidence: 99%

“…Acidic pH and anaerobic conditions, often encountered in the rhizosphere, increase ipdC expression in A. brasilense Sp245 (43,61), while in E. herbicola 299R, osmotic stress and low water availability induce ipdC expression (10). High levels of IAA accumulate in culture media only after entrance into the stationary phase in A. brasilense Sp7 and Sp245 and in E. cloacae UW5 (14,44,61). Consistent with this, the highest expression levels of ipdC were observed in stationary phase in A. brasilense Sp7 and E. cloacae UW5, and it is known that the stationaryphase sigma factor RpoS upregulates ipdC expression in E. cloacae UW5 and E. herbicola 299R (12,14,44).…”

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confidence: 99%

“…High levels of IAA accumulate in culture media only after entrance into the stationary phase in A. brasilense Sp7 and Sp245 and in E. cloacae UW5 (14,44,61). Consistent with this, the highest expression levels of ipdC were observed in stationary phase in A. brasilense Sp7 and E. cloacae UW5, and it is known that the stationaryphase sigma factor RpoS upregulates ipdC expression in E. cloacae UW5 and E. herbicola 299R (12,14,44). IAA and other auxins induced expression of ipdC in A. brasilense Sp245, and an auxin-responsive element similar to that found in the promoters of some auxin-regulated plant genes was found in the ipdC promoter region (34,61).…”

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confidence: 99%

“…IAA is produced after oxidation of indole-3-acetaldehyde by indole-3-acetaldehyde oxidase. The key enzyme in this pathway, IPDC, is encoded by ipdC, and elimination of ipdC abolishes IAA biosynthesis in E. cloacae UW5 and greatly reduces IAA production in A. brasilense and E. herbicola 299R (11,14,17,45,51).…”

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Aromatic Amino Acid-Dependent Expression of Indole-3-Pyruvate Decarboxylase Is Regulated by TyrR in Enterobacter cloacae UW5

2008

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The plant growth-promoting rhizobacterium Enterobacter cloacae UW5 synthesizes the plant growth hormone indole-3-acetic acid (IAA) via the indole-3-pyruvate pathway utilizing the enzyme indole-3-pyruvate decarboxylase that is encoded by ipdC. In this bacterium, ipdC expression and IAA production occur in stationary phase and are induced by an exogenous source of tryptophan, conditions that are present in the rhizosphere. The aim of this study was to identify the regulatory protein that controls the expression of ipdC. We identified a sequence in the promoter region of ipdC that is highly similar to the recognition sequence for the Escherichia coli regulatory protein TyrR that regulates genes involved in aromatic amino acid transport and metabolism. Using a tyrR insertional mutant, we demonstrate that TyrR is required for IAA production and for induction of ipdC transcription. TyrR directly induces ipdC expression, as was determined by real-time quantitative reverse transcription-PCR, by ipdC promoter-driven reporter gene activity, and by electrophoretic mobility shift assays. Expression increases in response to tryptophan, phenylalanine, and tyrosine. This suggests that, in addition to its function in plant growth promotion, indolepyruvate decarboxylase may be important for aromatic amino acid uptake and/or metabolism.Auxins are an important class of phytohormones that are essential for many aspects of plant growth and development, including organogenesis; tropic responses; cellular processes such as cell expansion, division, and differentiation; and gene regulation (1,9,21,25,60). The predominant natural auxin is indole-3-acetic acid (IAA) (8,21,60). In addition to synthesis in plant tissues, many plant-associated bacteria also produce and secrete IAA that can influence the health of host plants. Production of IAA by some phytopathogenic bacteria causes plant diseases such as gall tumor formation by Agrobacterium tumefaciens, Erwinia herbicola pv. gypsophilae, and Pseudomonas syringae pv. savastanoi and necrotic lesions caused by Pseudomonas syringae pv. syringae (15,16,35,38,42,63). Loss of the ability to synthesize IAA, through mutagenesis, reduces the virulence of these pathogens (2, 16).Paradoxically, IAA produced by plant growth-promoting rhizobacteria (PGPR) has been found to enhance host root system development. Plant roots colonized with the PGPR species Azospirillum brasilense Sp6, Enterobacter cloacae UW5, and Pseudomonas putida GR12-2 displayed increases in root hair formation, the number and length of lateral roots, and/or primary root length that were dependent on bacterial IAA production. Mutants that were unable to synthesize IAA did not increase root proliferation (7,23,45,58,65). Well-developed root systems are important for natural nutrient uptake and for anchoring plants in soil. The differences in the effect of IAA produced by these two groups of bacteria may be due to differences in the levels of IAA production in planta or other contributing factors (46,57,65).A number of IAA biosynthetic ...

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confidence: 80%

Section: Vol 190 2008mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Aromatic Amino Acid-Dependent Expression of Indole-3-Pyruvate Decarboxylase Is Regulated by TyrR in Enterobacter cloacae UW5

2008

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Involvement of Quinolinate Phosphoribosyl Transferase in Promotion of Potato Growth by a Burkholderia Strain

Wang

Conn

Lazarovits

2006

Appl Environ Microbiol

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Burkholderia sp. strain PsJN stimulates root growth of potato explants compared to uninoculated controls under gnotobiotic conditions. In order to determine the mechanism by which this growth stimulation occurs, we used Tn5 mutagenesis to produce a mutant, H41, which exhibited no growth-promoting activity but was able to colonize potato plants as well as the wild-type strain. The gene associated with the loss of growth promotion in H41 was shown to exhibit 65% identity at the amino acid level to the nadC gene encoding quinolinate phosphoribosyltransferase (QAPRTase) in Ralstonia solanacearum. Complementation of H41 with QAPRTase restored growth promotion of potato explants by this mutant. Expression of the gene identified in Escherichia coli yielded a protein with QAPRTase activities that catalyzed the de novo formation of nicotinic acid mononucleotide (NaMN). Two other genes involved in the same enzymatic pathway, nadA and nadB, were physically linked to nadC. The nadA gene was cotranscribed with nadC as an operon in wild-type strain PsJN, while the nadB gene was located downstream of the nadA-nadC operon. Growth promotion by H41 was fully restored by addition of NaMN to the tissue culture medium. These data suggested that QAPRTase may play a role in the signal pathway for promotion of plant growth by PsJN.

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Isolation and characterization of indole acetic acid (IAA) producing bacteria from rhizospheric soil and its effect on plant growth

Mohite¹

2013

J. Soil Sci. Plant Nutr.

293

213

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Indole acetic acid (IAA) production is a major property of rhizosphere bacteria that stimulate and facilitate plant growth. The present work deals with isolation, characterization and identification of indole acetic acid producing bacteria from the rhizospheric soil. Out of ten Indole acetic acid producing isolates, five were selected as efficient producers. Optimization of indole acetic acid production was carried out at different cultural conditions of pH and temperature with varying media components such as carbon and nitrogen source, tryptophan concentration. Partial purification of IAA was done and purity was confirmed with Thin layer chromatography. Subsequently, effect on plant growth was tested by pot assay. In conclusion the study suggests the IAA producing bacteria as efficient biofertilizer inoculants to promote plant growth.

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Physiological Evidence for Novel Tryptophan-Dependent Pathway for Indole Acetic Acid Synthesis in Azospirillum brasilense

Cited by 3 publications

References 0 publications

Aromatic Amino Acid-Dependent Expression of Indole-3-Pyruvate Decarboxylase Is Regulated by TyrR in Enterobacter cloacae UW5

Aromatic Amino Acid-Dependent Expression of Indole-3-Pyruvate Decarboxylase Is Regulated by TyrR in Enterobacter cloacae UW5

Involvement of Quinolinate Phosphoribosyl Transferase in Promotion of Potato Growth by a Burkholderia Strain

Isolation and characterization of indole acetic acid (IAA) producing bacteria from rhizospheric soil and its effect on plant growth

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