Functional differences between galactolipids and glucolipids revealed in photosynthesis of higher plants.
Galactolipids represent the most abundant lipid class in thylakoid membranes, where oxygenic photosynthesis is performed. The identification of galactolipids at specific sites within photosynthetic complexes by x-ray crystallography implies specific roles for galactolipids during photosynthetic electron transport. The preference for galactose and not for the more abundant sugar glucose in thylakoid lipids and their specific roles in photosynthesis are not understood. Introduction of a bacterial glucosyltransferase from Chloroflexus aurantiacus into the galactolipid-deficient dgd1 mutant of Arabidopsis thaliana resulted in the accumulation of a glucose-containing lipid in the thylakoids. At the same time, the growth defect of the dgd1 mutant was complemented. However, the degree of trimerization of light-harvesting complex II and the photosynthetic quantum yield of transformed dgd1 plants were only partially restored. These results indicate that specific interactions of the galactolipid head group with photosynthetic protein complexes might explain the preference for galactose in thylakoid lipids of higher plants. Therefore, galactose in thylakoid lipids can be exchanged with glucose without severe effects on growth, but the presence of galactose is crucial to maintain maximal photosynthetic efficiency.
Hölzl
Georg
G
Department of Molecular Physiology, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm, Germany.
Witt
Sandra
S
Kelly
Amélie A
AA
Zähringer
Ulrich
U
Warnecke
Dirk
D
Dörmann
Peter
P
Heinz
Ernst
E
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002236:Carbohydrate Conformation; D041861:Chloroflexus / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D005690:Galactose / Q000378:metabolism*; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism*; D006017:Glycolipids / Q000378:metabolism*; D016695:Glycosyltransferases / Q000378:metabolism; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding
D029681:Arabidopsis Proteins; D005227:Fatty Acids; D006017:Glycolipids; D045342:Light-Harvesting Protein Complexes; D016695:Glycosyltransferases; C119967:DGD1 protein, Arabidopsis; D005700:Galactosyltransferases; D005947:Glucose; D005690:Galactose