3-Indolylacetonitrile: A Naturally Occurring Plant Growth Hormone

Jones, E. R. H.; Henbest, H. B.; Smith, G. F.; Bentley, J. A.

doi:10.1038/169485a0

Cited by 106 publications

(21 citation statements)

References 13 publications

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“…Although auxin biosynthesis has been well studied, the question of whether two enzymes are involved in the conversion of indole-3-acetonitrile to IAA has been neglected. In plants other than Arabidopsis (35) and cabbage (37), the presence of indole-3-acetonitrile has not been fully investigated, but the biosynthesis of IAA via indole-3-acetonitrile as an intermediate cannot be ruled out. Indole-3-acetonitrile and its derivatives were also detected in roots of the Chinese cabbage Brassica pekinensis, which enlarge to form "clubs" through infection with a plasmodial fungus Plasmodiophora brassicae (21).…”

Section: Resultsmentioning

confidence: 99%

Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium.

Kobayashi

Suzuki

Fujita

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

115

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The occurrence of a hitherto unknown pathway involving the action of two enzymes, a nitrile hydratase and an amidase for the biosynthesis of indole-3-acetic acid was discovered in phytopathogenic bacteria Agrobacterium tumefaciens and in leguminous bacteria Rhizobium. The nitrile hydratase acting on indole-3-acetonitrile was purified to homogeneity through only two steps from the cell-free extract ofA. tumefaciens. The molecular mass of the purified enzyme estimated by HPLC was about 102 kDa, and the enzyme consisted of four subunits identical in molecular mass. The enzyme exhibited a broad absorption spectrum in the visible range with absorption maxima at 408 nm and 705 nm, and it contained cobalt and iron. The enzyme stoichiometrically catalyzed the hydration of indole-3-acetonitrile into indole-3-acetamide with a specific activity of 13.7 ,umol per min per mg and a Km of 7.9 ,uM.Indole-3-acetic acid (IAA) is a well-known phytohormone and three biosynthetic routes involving indole-3-pyruvate, tryptamine, or indole-3-acetonitrile have been studied in higher plants (1, 2). In the indole-3-acetonitrile route, the nitrile generated from indole-3-acetaldoxime, naturally occurring in plants (3), by indoleacetaldoxime dehydratase (EC 4.2.1.29) (4) or from indole-3-methylglucosinolate by myrosinase (EC 3.2.3.1) (5), is converted into IAA by nitrilase (EC 3.5.5.1) in Brassicaceae (cabbage group and radish), Gramineae (grasses), and Musaceae (banana family) (6, 7). While studies on auxin have been made for >100 years (8), none of the genes encoding IAA-forming enzymes in the indole-3-pyruvate or the tryptamine route have been cloned yet, although cDNA cloning of nitrilases fromArabidopsis thaliana (9-11) has been reported.Microbial production of plant hormones such as IAA and cytokinin seems to be essential for the virulence of bacteria in their host plants (12). Agrobacterium tumefaciens (Ag. tumefaciens) can infect wound sites on a wide range of dicotyledonous plants and cause the formation of crown gall tumors by transfer of the transferred DNA (T-DNA) region in the Ti plasmid from the bacteria into plant cells. The T-DNA genes tms-1 and tms-2 encode tryptophan 2-monooxygenase (EC 1.13.12.3) and indoleacetamide hydrolase, respectively (13); IAA is produced from tryptophan by the sequential action of these two enzymes. A similar situation in the genes responsible for IAA synthesis was observed in Pseudomonas savastanoi (Ps. savastanoi), which induced tissue proliferation in olive and oleander plants (14).In studying nitrile metabolism, we have found that the microbial degradation of nitriles can proceed by two enzymatic pathways (15). In one, a nitrilase catalyzes the direct conversion of nitriles into the corresponding acids plus ammonia (Eq. 1) (16). Yamada and coworkers (17) in our laboratory have purified and characterized such a nitrilase from Alcaligenes faecalis acting on indole-3-acetonitrile, and we have cloned (18) the gene. In the other pathway, a nitrile hydratase catalyzes the hydration of nitrile...

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Section: Resultsmentioning

confidence: 99%

Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium.

Kobayashi

Suzuki

Fujita

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

115

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“…Following the report of JONES et al (10) that indoleacetonitrile is activ-e in causing the elongation of Avena coleoptile sections a number of nitriles were tested. As shown in table II a-naphthaleneacetonitrile is as active as IAA and more active than naphthaleneacetic acid, and phenylacetonitrile is more active than phenylacetic acid.…”

Section: Resultsmentioning

confidence: 99%

On the Mechanism of Action of Growth Regulators

Muir¹,

Hansch²

1953

Plant Physiol.

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“…When IAN was isolated from crucifers by Jones et al (7), and shown to possess auxin activity up to 10 times as great as that of IAA in the Avena coleoptile straight growth test, it was concluded (3) that the activity could not be due to its conversion to IAA. 1 Received May 13,1963.…”

Section: Introductionmentioning

confidence: 99%

Uptake of Indole-3-acetic Acid and Indole-3-acetonitrile by Avena Coleoptile Sections

Poole

Thimann

1964

Plant Physiol.

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PLANT PHYSIOLOGY showed reliable responses to rapid change in water conditions of plants. With proper calibrations, leaf water and internal water (relative turgidity or diffusion pressure deficit) changes can be followed. AcknowledgmentThe authors gratefully acknowledge the help of Dr. Carl Ehlig, U.S. Salinity Laboratory, for providing the equipment and assistance in making the DPD measurements of cotton plants and Dr. C. H. 'M. van

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3-Indolylacetonitrile: A Naturally Occurring Plant Growth Hormone

Cited by 106 publications

References 13 publications

Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium.

Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria, Agrobacterium and Rhizobium.

On the Mechanism of Action of Growth Regulators

Uptake of Indole-3-acetic Acid and Indole-3-acetonitrile by Avena Coleoptile Sections

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