PLANT PHYSIOLOGY , Vol 102, Issue 1 213-218, Copyright © 1993 by American Society of Plant Biologists
|
CELL BIOLOGY AND SIGNAL TRANSDUCTION |
Modification of Phospholipid Catabolism in Microsomal Membranes of [gamma]-Irradiated Cauliflower (Brassica oleracea L.)
R. Voisine, L. P. Vezina and C. Willemot
Department of Food Science and Technology, Universite Laval, Quebec, Canada, G1K 7P4 (R.V., C.W.)
Acceleration of membrane deterioration has been observed recently during
storage of [gamma]-irradiated cauliflower (Brassica oleracea L., Botrytis
group). In the present study, the activity of microsome-associated
lipolytic enzymes was investigated in cauliflower florets exposed to 0 or 4
kilograys of [gamma] radiation and stored for 8 d at 13[deg]C. Radiolabeled
breakdown products obtained from the metabolism of
(16:0/18:2*)-phosphatidylcholine and
(16:0/16:0)-phosphatidyl-[N-methyl-3H]choline by microsomal membranes
indicated that phospholipase D (EC 3.1.4.4), phosphatidic acid phosphatase
(EC 3.1.3.4), and lipolytic acyl hydrolase were associated with the
membranes. The rate of phosphatidylcholine catabolism by the membranes
increased slowly in control cauliflower during storage. [gamma] irradiation
caused an immediate rise in phosphatidylcholine catabolism that remained
higher than that of the controls during subsequent storage. Collectively,
the data suggest that enhancement of membrane lipolytic activity results
from free-radical-induced stress. Rapid increase of the membrane-associated
phospholipase D activity may be a key event leading to accelerated membrane
deterioration following [gamma] irradiation.