This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by Cowan, A. K. Articles by Railton, I. D. Search for Related Content PubMed PubMed Citation Articles by Cowan, A. K. Articles by Railton, I. D. Agricola Articles by Cowan, A. K. Articles by Railton, I. D.

Metabolism and Enzymology

The Catabolism of (±)-Abscisic Acid by Excised Leaves of Hordeum vulgare L. cv Dyan and Its Modification by Chemical and Environmental Factors ¹

Plant Growth Laboratory, Department of Plant Sciences, Rhodes University, Grahamstown 6140, South Africa

Excised light-grown leaves and etiolated leaves of Hordeum vulgare L. cv Dyan catabolized applied (±)-[2-¹⁴C]abscisic acid ([±]-[2-¹⁴C]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 chromatographymass 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. By selecting tissue samples in which endogenous catabolites were undetectable by gas chromatography, it was possible to identify unequivocally ABA catabolites by GC-MS without the need to employ deuteriated substrate to distinguish the (±)-ABA catabolites from the same endogenous compounds. Refeeding studies were used to confirm the catabolic route. The methyl ester of (±)-[2¹⁴C]-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.

This article has been cited by other articles:

				L. Kong and P. von Aderkas Genotype effects on ABA consumption and somatic embryo maturation in interior spruce (Picea glauca x engelmanni) J. Exp. Bot., April 1, 2007; 58(6): 1525 - 1531. [Abstract] [Full Text] [PDF]

				P. E. Verslues and E. A. Bray Role of abscisic acid (ABA) and Arabidopsis thaliana ABA-insensitive loci in low water potential-induced ABA and proline accumulation J. Exp. Bot., January 1, 2006; 57(1): 201 - 212. [Abstract] [Full Text] [PDF]

				A. A.C. Alves and T. L. Setter Response of Cassava to Water Deficit: Leaf Area Growth and Abscisic Acid Crop Sci., January 1, 2000; 40(1): 131 - 137. [Abstract] [Full Text]