Effect of gibberellic acid on growth and indole metabolism of dwarf-pea plants
A study was conducted to describe the pathway of biosynthesis of indole-3-acetic acid (IAA) from tryptophan (TPP) and determine the effect of gibberellic acid (GA/sub 3/) on this system. Treatment of dwarf peas (Pisum sativum L. var Little Marvel) with 0.8 ..mu..g GA/sub 3//plant resulted in increase in plant height along with increased auxin level. A cell-free preparation of pea shoot tissue was able to convert D,L-tryptophan-3-/sup 14/C into different indole metabolites. The acidic and neutral fractions obtained after TPP incubation were subjected to thin-layer chromatography. In the neutral fraction, two peaks of radioactivity were found and these matched the Rfs for indole-acetaldehyde (IAAId) and indole-3-ethanol (IEt). One major peak of radioactivity was observed in the radiochromatograms of the acidic fraction and it corresponded with a authentic IAA. The enzymes involved in the conversion of TPP to IAA involved, in the first step, a transaminase (tryptophan aminotransferase, EC 2 x 6 x 1) reaction. The aminotransferase was purified about 82-fold by acetone precipitation and Sephadex G-200 filtration. It had a pH optimum of 8.5 and a temperature optimum of 40/sup 0/C. With ..cap alpha..-ketoglutarate a co-substrate, the enzyme transaminated aromatic as well as aliphatic amino acids including D,L-tryptophan, D,L-alanine and D,L leucine. D-TPP was found to be more effective than L-TPP as a substrate. GA/sub 3/ treatment to dwarf pea plants results in increase in the specific activity of the enzyme over the observation period. In the second step of TPP conversion, IPyA is decarboxylated by an enzyme to IAAId. In plants treated with GA/sub 3/, the enzyme activity was significantly higher three days after treatment but remained unaffected at all other stages when observations were made. The final step enzyme is a dehydrogenase that can convert IAAId to IAA in the presence of MAD as a co-factor.
- Research Organization:
- City Univ. of New York, NY (USA)
- OSTI ID:
- 7140847
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALANINES
AMINO ACIDS
AMINOTRANSFERASES
AROMATICS
AZAARENES
AZOLES
BACTERIA
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CHROMATOGRAPHY
ENZYME ACTIVITY
ENZYMES
ESTERS
GIBBERELLIC ACID
GROWTH
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
INDOLES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LACTONES
LEGUMINOSAE
LEUCINE
METABOLISM
METABOLITES
MICROORGANISMS
NITROGEN TRANSFERASES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PISUM
PLANT GROWTH
PLANTS
PYRROLES
RESPONSE MODIFYING FACTORS
RHIZOBIUM
SEPARATION PROCESSES
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
TRYPTOPHAN