title: Digalactosyldiacylglycerol is essential in Synechococcus elongatus PCC 7942, but its function does not depend on its biosynthetic pathway.
abstract: Digalactosyldiacylglycerol (DGDG) is a major component of thylakoid membranes, occupying approximately 20% of the membrane system. This lipid composition is conserved from cyanobacteria to the chloroplasts of terrestrial plants, suggesting that DGDG is important for the function of photosynthetic membranes. Here we isolated the gene for DGDG synthase in the cyanobacterium Synechococcus elongatus PCC 7942 (7942dgdA) and found that this gene is essential for this species. 7942dgdA could be knocked out only when genes for cyanobacterial or plant DGDG synthases were expressed, indicating that the important factor was not the specific synthetic pathway but the lipid product. Lack of DGDG could not be compensated by the other membrane lipids in S. elongatus PCC 7942 or by glucosylgalactosyldiacylglycerol synthesized by the β-GlcT gene of Chloroflexus aurantiacus. These results reveal that DGDG has an indispensable role in S. elongatus PCC 7942 and that the second galactose molecule is key. Conservation and distribution of the galactolipid synthetic pathway among oxygenic phototrophs is discussed. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.
authors.affiliation: Department of Biological Science, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Maida
authors.affiliation: Department of Biological Science, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan; Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8011, Japan; PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan. Electronic address: awai.koichiro@shizuoka.ac.jp.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Awai
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology; D038983:Galactolipids / Q000235:genetics* / Q000378:metabolism; D005700:Galactosyltransferases / Q000235:genetics* / Q000378:metabolism; D008563:Membrane Lipids / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000235:genetics; D046940:Synechococcus / Q000201:enzymology / Q000235:genetics*; D020524:Thylakoids / Q000201:enzymology
chemical_list: D029681:Arabidopsis Proteins; D038983:Galactolipids; D008563:Membrane Lipids; C007388:digalactosyldiacylglycerol; C119967:DGD1 protein, Arabidopsis; D005700:Galactosyltransferases
keywords: Cyanobacteria; Digalactosyldiacylglycerol; Galactolipid; Monogalactosyldiacylglycerol; Thylakoid membranes