Biochemical aspects of membrane morphogenesis in germinating wheat

• Main Author: Brearly, C. A.
• Published: Swansea University 1986
• Subjects: 571.2
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636145

Radiolabelling studies were employed to investigate gibberellic acid mediated control of phospholipid synthesis in the aleurone tissue of germinating wheat. Particular emphasis was placed on the initial 24 hours of germination. Pulse-chase experiments were performed to investigate the turnover of phosphatidylcholine and the effects of gibberellic acid thereon. Existing fractionation procedures were modified to limit the lipolytic losses of membrane lipid during subcellular fractionation. Water-soluble compounds were tested for their efficacy in inhibiting the high endogenous levels of phospholipase D activity present in the tissue. Subcellular fractions of the tissue were charaecterised by electron microscopy and morphometric analyses were made. Radiolabelling studies indicated that the aleurone grain/spherosome complex is the major site of phospholipid synthesis at early stages of germination. At later stages the pattern of labelling was shifted towards microsomal fractions. Studies of phospholipid turnover revealed a very rapid turnover of (Me-14C) choline-labelled phosphatidylcholine in the aleurone grain and spherosome-containing fractions and slower turnover in microsome containing fractions. Gibberellic acid caused a reduction in the turnover of (Me-14C) choline-labelled phosphatidylcholine. A study was made of the effects of gibberellic acid on the CDP-base pathway of phosphatidylcholine synthesis. The experiments performed suggested that the CDP-base pathway could not account for the observed radiolabelling of phosphatidylcholine. The results of experiments detailed in this thesis are discussed in relation to the control of phospholipid synthesis and the morphogenesis of the endomembrane system in the aleurone tissue.