Effects of Light on the Metabolism of Glycerolipids in Plastidial and Cytoplasmic Membranes of Wheat Leaves: Studies in Vivo and in Vitro |
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Authors: | Bahl Jacqueline; Alpha Marie-Jose |
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Institution: | Laboratoire dt Biologie Végétale IV, C.N.R.S. (U.A. 1180), Université Pierre et Marie Curie 12 rue Cuvier, 75005 Paris, France |
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Abstract: | Wheat leaves were labelled with l-14C]-glycerol or l-14C]-acetateand chase experiments performed in the dark or under light.In plastids, both in the dark and under light, the results indicatea transfer of l-14C]-glycerol from phospholipids to galactolipidsand of l-14C]-acetate from phosphatidylcholine (PC) to monogalactosyldiacylglycerol (MGDG). They also argue for a transfer of l-14C]-glyceroland 1-14C]-acetate from phosphatidylcholine (PC) to phosphatidylethanolamine(PE) in extraplastidial membranes. During chase experimentsin the dark, the chloroplasts accumulated higher amounts ofradioactive precursor in saturated fatty acids. In the darkor under light, oleoyl-PC labelling equally decreased in plastids,but decreased much more under light in extraplastidial membranes.Light enhanced polyunsaturated fatty acid synthesis, mainlyin MGDG, PC, PE and plastidial phosphatidylglycerol (PG). In the dark or under light, all glycerolipids were labelledwhen purified plastids were incubated with l-14C]-acetate.Light stimulated the incorporation of the label in palmitoyl-MGDG,PG and sulfoquinovosyldiacylglycerol (SL) and also the transferof oleate from PC to MGDG. Only under light and when extraplastidialmembranes were added to isolated plastids, linoleoyl-MGDG, PGand PC were slightly labelled. These results argue for a stimulating effect of light on glycerolipidsynthesis in wheat leaf chloroplasts, on the transfer of oleatefrom PC to MGDG and on the desaturase activity. (Received March 8, 1986; Accepted September 26, 1986) |
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