Metabolism of radiolabelled galactolipids in senescent barley leaves |
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| Affiliation: | 1. Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, São Paulo 09972-270, Brazil;2. Center of Natural and Human Sciences, Federal University of ABC, Santo André 09210-580, Brazil;3. Center for Parasitology and Mycology, Adolfo Lutz Institute, São Paulo 01246-000, Brazil;4. Nucleus of Research in Physiology and Biochemistry, Institute of Botany of São Paulo, São Paulo 04301-902, Brazil;5. Institute of Food Chemistry, Technische Universität Braunschweig, Braunschweig 38106, Germany;1. Department of Natural Products Chemistry, Shenyang Pharmaceutical University, Shenyang 110016, PR China;2. Key Laboratory of Structure-Based Drug Design and Discovery, Ministry of Education, Shenyang Pharmaceutical University, Shenyang 110016, PR China;1. Universität Bayreuth, Universitätsstrasse 30, D-95440 Bayreuth, Germany;2. Université Joseph Fourier, LBFA, BP53, F-38041 Grenoble cedex 9, France;1. The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow, Poland;2. Institute of Biology, The Jan Kochanowski University, Świętokrzyska 15, 25-406 Kielce, Poland;3. Department of Medical Chemistry, Faculty of Pharmacy, Medical University Lublin, Jaczewskiego 4, 20-090 Lublin, Poland;4. Institute of Botany, Christian-Albrechts-University of Kiel, Olshausenstrasse 40, 24098 Kiel, Germany |
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| Abstract: | The metabolism of galactolipids in senescent primary leaves of barley was followed upon the incorporation of [1-14C]oleic acid during greening of etiolated shoots. In presenscent leaves the bulk of the label was present in apolar compounds of which 36% were galactolipids and 57% phospholipids. In segments induced to senesce in continouos darkness the loss of the predominant 18:3/18:3 molecular species of galactolipids was accompanied by the temporary accumulation of 18:3/18:3 phosphatidylcholine, a species which was almost absent in the presenescent leaves. A large proportion of radiocactivity lost in the galactolipids was eventually released as CO2. Label was also transferred to sugars and other polar compounds. A pathway of galactolipid breakdown featuring the conversion of the diacylglycerol cores to phosphatidylcholine followed by the release of free fatty acids in glyoxisome-like microbodies and gluconeogenesis via β-oxidation and the glyoxylic acid cycle is proposed. |
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