PLANT PHYSIOLOGY , Vol 102, Issue 2 565-571, Copyright © 1993 by American Society of Plant Biologists
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METABOLISM AND ENZYMOLOGY |
Developmental Profile of Diacylglycerol Acyltransferase in Maturing Seeds of Oilseed Rape and Safflower and Microspore-Derived Cultures of Oilseed Rape
R. J. Weselake, M. K. Pomeroy, T. L. Furukawa, J. L. Golden, D. B. Little and A. Laroche
Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada, T1K 3M4 (R.J.W., T.L.F., J.L.G., D.B.L)
Diacylglycerol acyltransferase (EC 2.3.1.20) activity was assayed during
the maturation of seeds of oilseed rape (Brassica napus L.) and safflower
(Carthamus tinctorius L.). Developmental studies were also conducted with
microspore-derived embryos of oilseed rape (B. napus L. cv Topas) and an
embryogenic microspore-derived cell-suspension culture of winter oilseed
rape (B. napus L. cv Jet Neuf). In the maturing seeds, diacylglycerol
acyltransferase activity increased to a maximum during rapid accumulation
of lipid and declined, thereafter, with seed maturity. In
microspore-derived embryos of oilseed rape (cv Topas), high levels of
diacylglycerol acyltransferase activity were found throughout the early
torpedo to late cotyledonary developmental stages with maximum enzyme
specific activity associated with the mid-cotyledonary developmental stage.
The cell-suspension culture of winter oilseed rape (cv Jet Neuf) contained
3 to 4% triacylglycerol on a dry weight basis and represented about half of
the total lipid. The fatty acid profile of total lipid and triacylglycerol
in the cell-suspension culture was similar in samples taken during a 1-year
period. The Jet Neuf culture contained diacylglycerol acyltransferase with
specific activity similar to that of Topas microspore-derived embryos. Jet
Neuf diacylglycerol acyltransferase also displayed an enhanced specificity
for erucoyl-CoA over oleoyl-CoA when assayed with 14 [mu]M acyl-coenzyme A
in the reaction mixture. The specific activity of diacylglycerol
acyltransferase in homogenates prepared from the Jet Neuf culture ranged
from 5 to 15 pmol of triacylglycerol min-1 mg-1 of protein when assayed at
intervals during a period of 1 year. Thus, the cell-suspension culture may
represent an attractive tissue source for purification and characterization
of triacyl-glycerol biosynthetic enzymes.
