Hormonal regulation of oil accumulation in Brassica seeds: Metabolism and biological activity of ABA, 7′-, 8′- and 9′-hydroxy ABA in microspore derived embryos of B. napus

• Published in: Phytochemistry (Oxford) Vol. 69; no. 15; pp. 2678 - 2688
• Main Authors: Jadhav, Ashok S., Taylor, David C., Giblin, Michael, Ferrie, Alison M.R., Ambrose, Stephen J., Ross, Andrew R.S., Nelson, Ken M., Irina Zaharia, L., Sharma, Nirmala, Anderson, Maureen, Fobert, Pierre R., Abrams, Suzanne R.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 01.11.2008; Elsevier
• Subjects: Abscisic acid; Abscisic Acid - metabolism; Abscisic Acid - pharmacology; Acetyltransferases - metabolism; acyltransferases; Biochemistry & Molecular Biology; Biological and medical sciences; Brassica napus; Brassica napus - embryology; Brassica napus - genetics; Brassica napus - metabolism; Brassicanapus; Chemical constitution; Fatty Acids, Monounsaturated - metabolism; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant - drug effects; Hormones - metabolism; Hormones - pharmacology; Hydroxylated ABA metabolites; Life Sciences & Biomedicine; microspores; Oil accumulation; Oils - metabolism; oilseeds; oleosin; plant hormones; Plant physiology and development; Plant Proteins - genetics; Plant Sciences; Science & Technology; Seed development; seed oils; Seeds - embryology; Seeds - genetics; Seeds - metabolism; Spores - metabolism; Triglycerides - metabolism; Oil accumulation; Brassica napus; Abscisic acid; Hydroxylated ABA metabolites; Seed development; CATABOLISM; ABSCISIC-ACID ANALOGS; INDUCTION; DORMANCY; MASS-SPECTROMETRY; BIOSYNTHESIS; ARABIDOPSIS SEEDS; L-CV-RESTON; (+)-ABSCISIC ACID; 8'-HYDROXYLASES; Embryo; Seeds; Vegetable oil; Accumulation; Regulation(control); Cruciferae; Dicotyledones; Angiospermae; Development; Hydroxylation; Chemical structure; Metabolism; Biological activity; Oil; Seed; Microspore; Plant origin; Spermatophyta; Pharmacokinetics; Oil plant (vegetal)
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2008.08.010

Isotopically labeled ABA and its hydroxylated metabolites, 7’-, 8’- and 9’- hydroxy ABA, were supplied to microspore-derived embryos of Brassica napus cv Hero. All compounds included expression of oleosin and fatty acid elongase genes and increased the accumulation of triacylglycerois and very long chain fatty acids. Developing seeds of Brassica napus contain significant levels of ABA and products of oxidation at the 7′- and 9′-methyl groups of ABA, 7′- and 9′-hydroxy ABA, as well stable products of oxidation of the 8′-methyl group, phaseic acid and dihydrophaseic acid. To probe the biological roles of the initially formed hydroxylated compounds, we have compared the effects of supplied ABA and the hydroxylated metabolites in regulating oil synthesis in microspore-derived embryos of B. napus, cv Hero that accumulate long chain fatty acids. Uptake into the embryos and metabolism of each of the hormone metabolites was studied by using deuterium labeled analogs. Supplied ABA, which was rapidly metabolized, induced expression of oleosin and fatty acid elongase genes and increased the accumulation of triacylglycerols and very long chain fatty acids. The metabolites 7′- and 9′-hydroxy ABA had similar effects, with the 9′-hydroxy ABA having even greater activity than ABA. The principal catabolite of ABA, 8′-hydroxy ABA, also had hormonal activity and led to increased oil synthesis but induced the genes weakly. These results indicate that all compounds tested could be involved in lipid synthesis in B. napus, and may have hormonal roles in other ABA-regulated processes.