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Identification and functional analysis of a new triacylglycerol-lipasefamily in Arabidopsis thaliana Martina Körner, Maike Rudolph, Xuan Wang, Karin Athenstaedt 1 , Günther Daum 1 and Ivo Feussner Georg-August-University Göttingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Jusutus-von-Liebig-Weg 11, D-37077 Göttingen, Germany 1 Technical University Graz, Institute for Biochemistry, Petersgasse 12/2, A-8010 Graz, Austria. Many organisms accumulate carbon skeletons in the form of triacylglycerol (TAG) that is stored in lipid bodies. In plants lipid bodies are found in many tissues and are particularly abundant in seeds, where upon germination the TAG is broken down to fuel post-germinative growth. The initial step is catalysed by a lipase, which hydrolyses TAG at the lipid body surface. Little is k<strong>now</strong>n about the molecular identity of these TAGhydrolysing lipases (TGLs) in plants. In order to identify this enzyme, a reverse genomic analysis was performed on the Arabidopsis genome. A protein of about 45-kDa was identified (AtTGL1), which shares homology with lipases from the GDSL-acylhydrolase family and is preferentially expressed in seedlings. In Arabidopsis it belongs to small gene family with 9 members (AtTGL1-9). AtTGL1 was expressed heterologously in E. coli and was characterized in detail after expression in insect cells. It was shown to hydrolyze triolein at a neutral to acid pH, but is neither active on phospholipids (PC, PI) nor on sterol esters and has no acyltransferase activity. In addition it complements a TGL mutant from yeast (tgl3). Transient expression studies in soybean embryos of AtTGL1-YFP were used to show that the protein is associated with the surface of lipid bodies. Moreover homozygous knock out lines of AtTGL1 failed to germinate in the absence of sucrose, and it is likely that AtTGL1 play an important role in regulating lipolysis during post-germinative growth.
Characterisation of sterol carrier protein-2. Johan Edqvist 1 , Bing Song Zheng 1 , Kristina Blomqvist 1 , Matts Nylund 2 , Lenita Viitanen 2 , Jessica Tuuf 2 , Tiina A. Salminen 2 , Peter Mattjus 2 1 Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, 750 07 UPPSALA, Sweden 2 Department of Biochemistry and Pharmacy, Åbo Akademi University, Artillerigatan 6 A III, FIN-20520 TURKU, Finland. We have recently shown that plants encode and express sterol carrier protein-2 (SCP- 2). The biological function of SCP-2 is unclear, although there are indications that at least the mammalian SCP-2 may be involved in the catabolism of branched-chain and very long chain fatty acids. Bacterial and archaean SCP-2 are expressed from separate, independent genes, while in eukaryotes SCP-2 is often expressed in the C-terminal of multi-domain proteins. However, according to current k<strong>now</strong>ledge plant SCP-2 is also expressed from independent, unfused genes. The A. thaliana locus At5g42890 encodes the A. thaliana SCP-2 (AtSCP-2), which is a 13.6 kDa protein with pI of 9.2. AtSCP-2 is predominantly localized to the peroxisomes. Structural models of apo-AtSCP-2 and the ligand-bound conformation of AtSCP-2 revealed high similarity with mammalian SCP-2like domains. The AtSCP-2 models in both forms have a similar hydrophobic ligandbinding tunnel, which is extremely suitable for lipid binding. AtSCP-2 protein has lipid transfer activity in vitro, showing a preference for phosphatidylcholine, ergosterol and phosphatidic acid. We have also cloned and characterised SCP-2 from Euphorbia lagascae. The amino acid sequence of ElSCP-2 shares 67% identity and 84% similarity with AtSCP-2. Although ElSCP-2 and AtSCP-2 have a high sequence identity some of their cavity amino acids are different, which might explain the divergent ligand-binding preference of the two proteins. Proteomic analysis revealed that ElSCP-2 protein is accumulating in the endosperm during seed germination. We are interested in understanding the biological function of SCP-2 and will present our recent results on function, expression, evolution, specificity and structure of SCP-2 from plants.
Page 1 and 2: Wednesday 17 August 2005 17:00-20:0
Page 3: Session G 14:00-14:30 The role of s
Page 7 and 8: Lipid storage in soybean seeds occu
Page 9 and 10: Extracellular BODYGUARD involved in
Page 11 and 12: Fatty acid metabolism in Arabidopsi
Page 13 and 14: Biochemical and structural analyses
Page 15 and 16: Biosynthesis and function of galact
Page 17 and 18: Functional role of phosphatidylglyc
Page 19 and 20: Linoleate biosynthesis and aroma bi
Page 21 and 22: Castor Oil Biosynthesis and Express
Page 23 and 24: Functions of Sterol Glycosides and
Page 25 and 26: Molecular basis for the elicitation
Page 27 and 28: Fungal sphingolipids as targets of
Page 29 and 30: The Use of Plant Lipids as Function
Page 31 and 32: Production of enzymes and industria
Page 33 and 34: Transgenic Oilseeds as a New Renewa
Page 35 and 36: Accumulation of medium-chain fatty
Page 37 and 38: Posters
Page 39 and 40: Application of pulsed electric fiel
Page 41 and 42: P4 Carbohydrate metabolism in devel
Page 43 and 44: Physical and structural properties
Page 45 and 46: P8 Phosphoinositide molecular speci
Page 47 and 48: Lipid metabolism in arbuscular myco
Page 49 and 50: Very Long Chain Fatty Acids in sunf
Page 51 and 52: P14 Phospholipid turnover in the pl
Page 53 and 54: P16 Composition of the surface waxe
Page 55 and 56:
Characterization of oxylipin produc
Page 57 and 58:
Profiling of labile plant oxylipins
Page 59 and 60:
Characterisation of a novel microso
Page 61 and 62:
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