Catabolism of (+/-)-abscisic acid by excised leaves of Hordeum vulgare L. cv Dyan and its modification by chemical and environmental factors

Journal Article · Fri May 01 04:00:00 EDT 1987 · Plant Physiol.; (United States)

DOI:https://doi.org/10.1104/pp.84.1.157· OSTI ID:6070923

Cowan, A K; Railton, I D

Excised light-grown leaves and etiolated leaves of Hordeum vulgare L. cv Dyan catabolized applied (+/-)-(2-/sup 14/C)abscisic acid ((+/-)-(2-/sup 14/C)ABA) to phaseic acid (PA), dihydrophaseic acid (DPA), and 2'-hydroxymethyl ABA (2'-HMABA). Identification of these catabolites was made by microchemical methods and by combined capillary gas chromatography-mass spectrometry (GC-MS) following high dose feeds of nonlabeled substrate to leaves. Circular dichroism analysis revealed that 2'-HMABA was derived from the (-) enantiomer of ABA. Refeeding studies were used to confirm the catabolic route. The methyl ester of (+/-)-(2/sup 14/C)-ABA was hydrolyzed efficiently by light-grown leaves of H. vulgare. Leaf age played a significant role in (+/-)-ABA catabolism, with younger leaves being less able than their older counterparts to catabolize this compound. The catabolism of (+/-)-ABA was inhibited markedly in water-stressed Hordeum leaves which was characterized by a decreased incorporation of label into 2'-HMABA, DPA, and conjugates. The specific, mixed function oxidase inhibitor, ancymidol, did not inhibit, dramatically (+/-)-ABA catabolism in light-grown leaves of Hordeum whereas the 80s ribosome, translational inhibitor, cycloheximide, inhibited this process markedly. The 70s ribosome translational inhibitors, lincomycin and chloramphenicol, were less effective than cycloheximide in inhibiting (+/-)-ABA catabolism, implying that cytoplasmic protein synthesis is necessary for the catabolism of (+/-)-ABA in Hordeum leaves whereas chloroplast protein synthesis plays only a minor role. This further suggests that the enzymes involved in (+/-)-ABA catabolism in this plant are cytoplasmically synthesized and are turned-over rapidly, although the enzyme responsible for glycosylating (+/-)-ABA itself appeared to be stable.

• Research Organization: Rhodes Univ., Grahamstown, South Africa
• OSTI ID: 6070923
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 84:1; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ABSCISIC ACID
AUXINS
BARLEY
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CATABOLISM
CEREALS
CHROMATOGRAPHY
ENANTIOMORPHS
ENZYME ACTIVITY
ENZYMES
GRASS
HYDROGEN COMPOUNDS
INHIBITION
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEAVES
MASS SPECTROSCOPY
METABOLISM
METABOLITES
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHYSIOLOGY
PLANT GROWTH REGULATORS
PLANTS
PROTEINS
SEPARATION PROCESSES
SPECTROSCOPY
SYNTHESIS
TRACER TECHNIQUES
WATER