Hj. Perry et Jl. Harwood, RADIOLABELING STUDIES OF ACYL LIPIDS IN DEVELOPING SEEDS OF BRASSICA-NAPUS - USE OF [1-C-14]ACETATE PRECURSOR, Phytochemistry, 33(2), 1993, pp. 329-333
[1-C-14]Acetate has been used to label fatty acids and complex lipids
in order to evaluate the capacity of embryos from developing oilseed r
ape seeds to synthesize lipid. Incorporation of radioactivity was line
ar for at least 4 hr. In terms of fresh weight, embryos about 20 days
after pollination (DAP) were most active whilst activity expressed per
embryo was high in the period 22-31 DAP, in agreement with the period
of rapid accumulation of oil in vivo. Major labelled classes were dia
cylglycerols (DAGs), triacylglycerols (TAGs) and polar lipids (PLs). T
he proportion of label in these fractions remained constant for embryo
s from seeds of different ages up to 41 DAP when the proportion of rad
ioactivity in DAGs declined from about 30 to 8% accompanied by a comme
nsurate rise in that of TAGs. Phosphatidylcholine (PtdCho) was the bes
t-labelled PL at all times of rapid lipid synthesis. After 41 DAP, the
amount of label in this phospholipid declined and there was increased
radioactivity in lysophosphatidylcholine (lysoPtdCho) and non-esterif
ied fatty acids (NEFAs), possibly indicating increased turnover of Ptd
Cho. The distribution of labelling within the fatty acids of individua
l lipid classes was studied and the results showed that the PLs contai
ned significantly more [C-14]palmitate and significantly less [C-14]ol
eate than the TAGs for embryos at all stages of development. The data
are discussed with regard to the possible influence of diacylglycerol
acyltransferase (DAGAT) activity in exerting significant flux control
during periods of rapid TAG accumulation.