Plant growth regulators and amino acids released by Azospirillum sp. in chemically defined media

Thuler, Daniela Strauss; Floh, Eny Iochevet Segal; Handro, Walter; Barbosa, Heloíza Ramos

doi:10.1046/j.1472-765x.2003.01373.x

Cited by 77 publications

(44 citation statements)

References 25 publications

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“…No significant differences in pH were found between cultures supplemented with IAA and those supplemented with PAA, indicating that the slightly higher expression of the ipdC gene in the presence of PAA can be intrinsically attributed to PAA itself and is not due to a pH effect. (30,41,10,58,43,57). Secondary metabolism is often brought on by exhaustion of a nutrient (suboptimal growth conditions), biosynthesis or addition of an inducer, or a growth rate decrease (16).…”

Section: Resultsmentioning

confidence: 99%

Azospirillum brasilense Produces the Auxin-Like Phenylacetic Acid by Using the Key Enzyme for Indole-3-Acetic Acid Biosynthesis

Somers

Ptacek

Gysegom

et al. 2005

Appl Environ Microbiol

134

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An antimicrobial compound was isolated from Azospirillum brasilense culture extracts by high-performance liquid chromatography and further identified by gas chromatography-mass spectrometry as the auxin-like molecule, phenylacetic acid (PAA). PAA synthesis was found to be mediated by the indole-3-pyruvate decarboxylase, previously identified as a key enzyme in indole-3-acetic acid (IAA) production in A. brasilense. In minimal growth medium, PAA biosynthesis by A. brasilense was only observed in the presence of phenylalanine (or precursors thereof). This observation suggests deamination of phenylalanine, decarboxylation of phenylpyruvate, and subsequent oxidation of phenylacetaldehyde as the most likely pathway for PAA synthesis. Expression analysis revealed that transcription of the ipdC gene is upregulated by PAA, as was previously described for IAA and synthetic auxins, indicating a positive feedback regulation. The synthesis of PAA by A. brasilense is discussed in relation to previously reported biocontrol properties of A. brasilense.Azospirillum is a well-studied genus of plant growth-promoting bacteria (PGPB), which colonizes the rhizosphere of numerous crop plants in tropical and subtropical regions (5, 6). Different mechanisms, such as phytohormone production, nitrate reduction, and nitrogen fixation, have been proposed to explain improved plant growth following inoculation with Azospirillum (5,7,9,22,37,38,53). The production of phytohormones, and more specifically the auxin indole-3-acetic acid (IAA), has been recognized as an important factor in direct plant-growth-promoting abilities of A. brasilense (5,18,19,37).Azospirillum sp. are not typical biocontrol agents of soilborne plant pathogens (5). Apart from some reports on bacteriocins and siderophores, no other antibacterial substances in Azospirillum sp. have been identified so far (39,40,50,55,60). However, there have been reports of moderate biocontrol capabilities of Azospirillum brasilense against crown gall disease, bacterial leaf blight of mulberry, and bacterial leaf and/or vascular diseases of tomato (1,3,4,46,54). In addition, A. brasilense can restrict the proliferation of other nonpathogenic rhizosphere bacteria (21). Nevertheless, the exact mechanisms involved in Azospirillum acting as a putative biocontrol agent are not yet known. Some reports therefore indicate that the protective mechanism may be indirectly explained by the plant growth promotion effect or by outcompeting other bacteria hosted by the same plant (3,46).In the present study, we attempted to further screen A. brasilense supernatant (extracts) for the presence of metabolites (besides IAA), which may be involved in the persistence of Azospirillum in the rhizosphere. This screening led to the identification of phenylacetic acid (PAA), an auxin-like molecule with antimicrobial activity. MATERIALS AND METHODSStrains, plasmids, media, and culture conditions. Strains and plasmids used in this study are listed in Table 1. A. brasilense was grown at 30°C in Luria-Bertani (LB) med...

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Section: Resultsmentioning

confidence: 99%

Azospirillum brasilense Produces the Auxin-Like Phenylacetic Acid by Using the Key Enzyme for Indole-3-Acetic Acid Biosynthesis

Somers

Ptacek

Gysegom

et al. 2005

Appl Environ Microbiol

134

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“…A recent study by Defez et al (2017) reported increases in nitrogenase activity in mutant strains of diazotrophic bacteria transformed to increase the production of IAA, indicating co-regulation of both IAA and BNF traits in different bacterial strains. The study by Thuler et al (2003) showed that Beijerinckia derxii can produce IAA at higher levels under BNF conditions. Nevertheless, the BNF activity and IAA biosynthesis were separated in time; while the BNF occur in early growth stage the IAA was increased at the stationary growth phase.…”

Section: Discussionmentioning

confidence: 99%

Ammonium excretion, auxin production and effects of maize inoculation with ethylenediamine-resistant mutants of Pseudomonas sp.

et al. 2018

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Plant growth-promoting bacteria (PGPB) comprise part of plant microbiome of biotechnological interest due to their potential to decrease the use of agrochemicals in agriculture.Among the commonly found PGPB species, the Pseudomonas genus is known for high competitiveness and efficiency in expressing growth-promotion traits. To increase the contribution of diazotrophic Pseudomonas sp. to the plant nitrogen nutrition, the strain AZM-01 was chemically mutagenized with methyl methanesulfonate (MMS), following the selection for resistance to ethylenediamine (EDA). From the 13 EDA-resistant mutant strains selected, four showed increased the ammonium excretion, with the highest value reaching up to 284% increase as compared to the wild strain, and six strains were found to produce significantly more auxins than the wild strain. Two independent inoculation trials with the wild and

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“…Apart from IAA, Azospirillum spp. are also known to produce other important plant hormones such as gibberellins, cytokinin, polyamines and amino acid that might have been involved to such growth effects (Thuler et al 2003;Cassán et al 2011). Previous studies demonstrated that PGPR-effect at the very early young stage of plant development is due to production of growth substances (Levanony 1990;Bashan, Holguin 1997;Barazani, Friedman 1999;Bashan, Jacoud et al 1999;Dobbelaere et al 1999;Bashan et al 2004).…”

Section: Effects Of Inoculation On Root and Shoot Growthmentioning

confidence: 99%

Early seedling growth response of lettuce, tomato and cucumber to Azospirillum brasilense inoculated by soaking and drenching

Mangmang

Deaker

Rogers

2015

Hort. Sci. (Prague)

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Mangmang J.S., Deaker R., Rogers G. (2015): Early seedling growth response of lettuce, tomato and cucumber to Azospirillum brasilense inoculated by soaking and drenching. Hort. Sci. (Prague), 42: 37-46.This study evaluated the effects of three A. brasilense strains (i.e. Sp7, Sp7-S and Sp245) on the early seedling growth of lettuce, tomato and cucumber. Seeds were inoculated by soaking and drenching before and after sowing, respectively. Results show that inoculation effect varied greatly with plant species, inoculation methods and PGPR strains which could be dependent on inoculum concentration and IAA (indole-3-acetic acid) production. Generally, the magnitude of inoculation impact on the early growth of vegetables was more pronounced with Sp7-S, followed by Sp245 and Sp7. In particular, Sp7-S and Sp245 strongly enhanced root and shoot growth, germination value and vigour of tomato when inoculated by soaking. Sp245 increased the level of endogenous plant IAA of cucumber and lettuce. Despite the diverse crop responses to inoculation methods, soaking appeared to be a better technique, and majority of the strains demonstrated more consistent beneficial effects on tomato.

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Plant growth regulators and amino acids released by Azospirillum sp. in chemically defined media

Cited by 77 publications

References 25 publications

Azospirillum brasilense Produces the Auxin-Like Phenylacetic Acid by Using the Key Enzyme for Indole-3-Acetic Acid Biosynthesis

Azospirillum brasilense Produces the Auxin-Like Phenylacetic Acid by Using the Key Enzyme for Indole-3-Acetic Acid Biosynthesis

Ammonium excretion, auxin production and effects of maize inoculation with ethylenediamine-resistant mutants of Pseudomonas sp.

Early seedling growth response of lettuce, tomato and cucumber to Azospirillum brasilense inoculated by soaking and drenching

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