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Lipid biosynthesis by isolated barley chloroplasts in relation to plastid development
C G Kannangara1, K W Henningsen, P K Stumpf
1Institute of Genetics, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen K., Denmark.
Plant Physiology
|November 1, 1971
Summary
Seedling age and greening time significantly impact barley plastid fatty acid synthesis. Older seedlings and longer greening periods enhance light-stimulated fatty acid synthesis, particularly in chloroplasts.
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- Plastids are key organelles for fatty acid synthesis in plants.
- Seedling age and light exposure are critical factors influencing plastid development and function.
- Understanding lipid metabolism in developing barley chloroplasts is crucial for agricultural science.
Purpose of the Study:
- To investigate how seedling age and greening duration affect lipid synthesis in barley plastids.
- To determine the influence of light intensity on fatty acid incorporation into plastid lipids.
- To elucidate the metabolic fate of acetate in developing barley chloroplasts.
Main Methods:
- Isolation of barley plastids from seedlings of varying ages and greening times.
- Incubation of isolated plastids with 1-(14)C-acetate to measure lipid synthesis.
- Analysis of radiolabel incorporation into different lipid classes (phospholipids, sulfolipids, digalactosyl diglyceride) and 6-methyl salicylic acid.
- Enzyme activity assays for acetyl CoA carboxylase.
Main Results:
- Plastids from 5-day-old seedlings showed limited fatty acid synthesis and no light stimulation.
- Plastids from older seedlings (7, 9, 11 days) exhibited increased fatty acid synthesis capacity and light responsiveness.
- High light exposure rapidly increased digalactosyl diglyceride labeling while decreasing 6-methyl salicylic acid labeling.
- Acetate incorporation shifted from 6-methyl salicylic acid to membrane lipids (palmitic and oleic acids) as greening progressed.
- Acetyl CoA carboxylase activity decreased during etioplast plastid differentiation into chloroplasts.
Conclusions:
- Seedling age and greening are essential for developing light-responsive fatty acid synthesis in barley plastids.
- Light intensity dynamically regulates lipid synthesis pathways, favoring membrane lipid production in mature chloroplasts.
- The metabolic pathway for acetate incorporation evolves significantly during chloroplast biogenesis.
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