AsianScientist (Oct. 13, 2014) – Scientists have shown for the first time that galactolipids are not necessary for photosynthesis, contrary to previously held notions. This research has been published in the Proceedings of the National Academy of Sciences.
Cyanobacteria are single-celled organisms that are capable of producing oxygen through photosynthesis and are believed to be the origin of the chloroplasts found inside the cells of plants and algae. Because galactolipids are the major components of the photosynthetic membranes in cyanobacteria, they have long been assumed to be necessary for either photosynthesis or at least for maintaining the flattened structure of the photosynthetic membranes.
In the present study, led by Professor Naoki Sato at the University of Tokyo, researchers have described the complete glycolipid biosynthesis pathway in cyanobacteria.
The mgdE gene encodes the epimerase that catalyzes the conversion of glucolipids (GlcDG) to galactolipids (MGDG). Only cyanobacteria have this gene. In contrast, in red algae and green plants, MGDG is directly synthesized by transfer of galactose to diacylglycerol. Credit: Naoki Sato/University of Tokyo.
Furthermore, they identified the gene mgdE that encodes an enzyme that converts glucolipid to galactolipid. By disrupting this gene, the group demonstrated that oxygenic photosynthesis is possible with a photosynthetic membrane consisting only of glucolipids, overturning the current understanding of the photosynthetic process.
Prof. Sato first proposed the route for glycolipid synthesis in his doctoral thesis 30 years ago. With this discovery, the genes for all the enzymes in the route for glycolipid synthesis have been identified.
The article can be found at: Awai et al. (2014) Oxygenic Photosynthesis Without Galactolipids.
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Source: University of Tokyo; Photo: Nat Tarbox/Flickr/CC.
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