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Postgerminative growth and lipid catabolism in oilseeds lacking the glyoxylate cycle
journal contribution
posted on 2023-05-18, 11:26 authored by Eastmond, PJ, Germain, V, Lange, PR, Bryce, JH, Steven SmithSteven Smith, Graham, IAThe glyoxylate cycle is regarded as essential for postgerminative growth and seedling establishment in oilseed plants. We have identified two allelic Arabidopsis mutants, icl-1 and icl-2, which lack the glyoxylate cycle because of the absence of the key enzyme isocitrate lyase. These mutants demonstrate that the glyoxylate cycle is not essential for germination. Furthermore, photosynthesis can compensate for the absence of the glyoxylate cycle during postgerminative growth, and only when light intensity or day length is decreased does seedling establishment become compromised. The provision of exogenous sugars can overcome this growth deficiency. The icl mutants also demonstrate that the glyoxylate cycle is important for seedling survival and recovery after prolonged dark conditions that approximate growth in nature. Surprisingly, despite their inability to catalyze the net conversion of acetate to carbohydrate, mutant seedlings are able to break down storage lipids. Results suggest that lipids can be used as a source of carbon for respiration in germinating oilseeds and that products of fatty acid catabolism can pass from the peroxisome to the mitochondrion independently of the glyoxylate cycle. However, an additional anaplerotic source of carbon is required for lipid breakdown and seedling establishment. This source can be provided by the glyoxylate cycle or, in its absence, by exogenous sucrose or photosynthesis.
History
Publication title
Proceedings of the National Academy of Sciences of The United States of AmericaVolume
97Issue
10Pagination
5669-5674ISSN
0027-8424Department/School
School of Natural SciencesPublisher
Natl Acad SciencesPlace of publication
2101 Constitution Ave Nw, Washington, USA, Dc, 20418Rights statement
Copyright 2000 The National Academy of SciencesRepository Status
- Restricted