Publications

• Three enzyme systems for galactoglycerolipid biosynthesis are coordinately regulated in plants.

  Benning C., Ohta H.

  Galactoglycerolipids, in which galactose is bound at the glycerol sn-3 position in O-glycosidic linkage to diacylglycerol, are abundant in plants and photosynthetic bacteria, where they constitute the bulk of the polar lipids of the photosynthetic membranes. Galactoglycerolipid biosynthesis in pla ... >> More

  Galactoglycerolipids, in which galactose is bound at the glycerol sn-3 position in O-glycosidic linkage to diacylglycerol, are abundant in plants and photosynthetic bacteria, where they constitute the bulk of the polar lipids of the photosynthetic membranes. Galactoglycerolipid biosynthesis in plants is highly compartmentalized involving enzymes at the endoplasmic reticulum and the two chloroplast envelopes. This peculiar organization requires extensive trafficking of lipid precursors. It is now increasingly apparent that there are three different sets of lipid galactosyltransferases capable of galactoglycerolipid biosynthesis in the model plant Arabidopsis. Two enzymes, MGD1 and DGD1, provide the bulk of galactoglycerolipids in the chloroplast and in photosynthetic tissues in general. Under phosphate-limited growth conditions and in non-photosynthetic tissues MGD2/3 and DGD2 are highly active. Moreover, galactoglycerolipids produced by this second pathway are often found in extraplastidic membranes. Although these galactosyltransferases use UDP-Gal as the galactose donor, a third pathway involves a processive enzyme, which transfers galactose from one galactolipid to another. << Less

  J. Biol. Chem. 280:2397-2400(2005) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• A role for SENSITIVE TO FREEZING2 in protecting chloroplasts against freeze-induced damage in Arabidopsis.

  Fourrier N., Bedard J., Lopez-Juez E., Barbrook A., Bowyer J., Jarvis P., Warren G., Thorlby G.

  <h4>Summary</h4>The sensitive to freezing2 (SFR2) gene has an important role in freezing tolerance in Arabidopsis thaliana. We show that homologous genes are present, and expressed, in a wide range of terrestrial plants, including species not able to tolerate freezing. Expression constructs derive ... >> More

  <h4>Summary</h4>The sensitive to freezing2 (SFR2) gene has an important role in freezing tolerance in Arabidopsis thaliana. We show that homologous genes are present, and expressed, in a wide range of terrestrial plants, including species not able to tolerate freezing. Expression constructs derived from the cDNAs of a number of different plant species, including examples not tolerant to freezing, are able to complement the freezing sensitivity of the Arabidopsis sfr2 mutant. In Arabidopsis the SFR2 protein is localized to the chloroplast outer envelope membrane, as revealed by the analysis of transgenic plants expressing SFR2 fusions to GFP, by confocal microscopy, and by the immunological analysis of isolated chloroplasts treated with thermolysin protease. Moreover, the chloroplasts of the sfr2 mutant show clear evidence of rapid damage after a freezing episode, suggesting a role for SFR2 in the protection of the chloroplast. << Less

  Plant J. 55:734-745(2008) [PubMed] [EuropePMC]

• Structural determinants allowing transferase activity in SENSITIVE TO FREEZING 2, classified as a family I glycosyl hydrolase.

  Roston R.L., Wang K., Kuhn L.A., Benning C.

  SENSITIVE TO FREEZING 2 (SFR2) is classified as a family I glycosyl hydrolase but has recently been shown to have galactosyltransferase activity in Arabidopsis thaliana. Natural occurrences of apparent glycosyl hydrolases acting as transferases are interesting from a biocatalysis standpoint, and k ... >> More

  SENSITIVE TO FREEZING 2 (SFR2) is classified as a family I glycosyl hydrolase but has recently been shown to have galactosyltransferase activity in Arabidopsis thaliana. Natural occurrences of apparent glycosyl hydrolases acting as transferases are interesting from a biocatalysis standpoint, and knowledge about the interconversion can assist in engineering SFR2 in crop plants to resist freezing. To understand how SFR2 evolved into a transferase, the relationship between its structure and function are investigated by activity assay, molecular modeling, and site-directed mutagenesis. SFR2 has no detectable hydrolase activity, although its catalytic site is highly conserved with that of family 1 glycosyl hydrolases. Three regions disparate from glycosyl hydrolases are identified as required for transferase activity as follows: a loop insertion, the C-terminal peptide, and a hydrophobic patch adjacent to the catalytic site. Rationales for the effects of these regions on the SFR2 mechanism are discussed. << Less

  J. Biol. Chem. 289:26089-26106(2014) [PubMed] [EuropePMC]

• Disruption of the two digalactosyldiacylglycerol synthase genes DGD1 and DGD2 in Arabidopsis reveals the existence of an additional enzyme of galactolipid synthesis.

  Kelly A.A., Froehlich J.E., Doermann P.

  Two genes (DGD1 and DGD2) are involved in the synthesis of the chloroplast lipid digalactosyldiacylglycerol (DGDG). The role of DGD2 for galactolipid synthesis was studied by isolating Arabidopsis T-DNA insertional mutant alleles (dgd2-1 and dgd2-2) and generating the double mutant line dgd1 dgd2. ... >> More

  Two genes (DGD1 and DGD2) are involved in the synthesis of the chloroplast lipid digalactosyldiacylglycerol (DGDG). The role of DGD2 for galactolipid synthesis was studied by isolating Arabidopsis T-DNA insertional mutant alleles (dgd2-1 and dgd2-2) and generating the double mutant line dgd1 dgd2. Whereas the growth and lipid composition of dgd2 were not affected, only trace amounts of DGDG were found in dgd1 dgd2. The growth and photosynthesis of dgd1 dgd2 were affected more severely compared with those of dgd1, indicating that the residual amount of DGDG in dgd1 is crucial for normal plant development. DGDG synthesis was increased after phosphate deprivation in the wild type, dgd1, and dgd2 but not in dgd1 dgd2. Therefore, DGD1 and DGD2 are involved in DGDG synthesis during phosphate deprivation. DGD2 was localized to the outer side of chloroplast envelope membranes. Like DGD2, heterologously expressed DGD1 uses UDP-galactose for galactosylation. Galactolipid synthesis activity for monogalactosyldiacylglycerol (MGDG), DGDG, and the unusual oligogalactolipids tri- and tetragalactosyldiacylglycerol was detected in isolated chloroplasts of all mutant lines, including dgd1 dgd2. Because dgd1 and dgd2 carry null mutations, an additional, processive galactolipid synthesis activity independent from DGD1 and DGD2 exists in Arabidopsis. This third activity, which is related to the Arabidopsis galactolipid:galactolipid galactosyltransferase, is localized to chloroplast envelope membranes and is capable of synthesizing DGDG from MGDG in the absence of UDP-galactose in vitro, but it does not contribute to net galactolipid synthesis in planta. << Less

  Plant Cell 15:2694-2706(2003) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Freezing tolerance in plants requires lipid remodeling at the outer chloroplast membrane.

  Moellering E.R., Muthan B., Benning C.

  Plants show complex adaptations to freezing that prevent cell damage caused by cellular dehydration. Lipid remodeling of cell membranes during dehydration is one critical mechanism countering loss of membrane integrity and cell death. SENSITIVE TO FREEZING 2 (SFR2), a gene essential for freezing t ... >> More

  Plants show complex adaptations to freezing that prevent cell damage caused by cellular dehydration. Lipid remodeling of cell membranes during dehydration is one critical mechanism countering loss of membrane integrity and cell death. SENSITIVE TO FREEZING 2 (SFR2), a gene essential for freezing tolerance in Arabidopsis, encodes a galactolipid remodeling enzyme of the outer chloroplast envelope membrane. SFR2 processively transfers galactosyl residues from the abundant monogalactolipid to different galactolipid acceptors, forming oligogalactolipids and diacylglycerol, which is further converted to triacylglycerol. The combined activity of SFR2 and triacylglycerol-biosynthetic enzymes leads to the removal of monogalactolipids from the envelope membrane, changing the ratio of bilayer-to non-bilayer-forming membrane lipids. This SFR2-based mechanism compensates for changes in organelle volume and stabilizes membranes during freezing. << Less

  Science 330:226-228(2010) [PubMed] [EuropePMC]