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.
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.
Jadhav
Ashok S
AS
National Research Council of Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9.
Taylor
David C
DC
Giblin
Michael
M
Ferrie
Alison M R
AM
Ambrose
Stephen J
SJ
Ross
Andrew R S
AR
Nelson
Ken M
KM
Irina Zaharia
L
L
Sharma
Nirmala
N
Anderson
Maureen
M
Fobert
Pierre R
PR
Abrams
Suzanne R
SR
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000123:Acetyltransferases / Q000378:metabolism; D029688:Brassica napus / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D000081031:Fatty Acid Elongases; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006728:Hormones / Q000378:metabolism* / Q000494:pharmacology; D009821:Oils / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics; D012639:Seeds / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D013170:Spores / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D005229:Fatty Acids, Monounsaturated; D006728:Hormones; D009821:Oils; D010940:Plant Proteins; D014280:Triglycerides; C079356:oleosin protein, Brassica napus; D000040:Abscisic Acid; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases