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P13 Spatial distribution of three microsomal oleate desaturase (FAD2) transcripts in sunflower developing seeds Alicia Sánchez-García 1 , Cecilia Gotor 2 , Luis C. Romero 2 , Manuel Mancha 1 , and José M. Martínez-Rivas 1 1 Instituto de la Grasa, CSIC, Sevilla, Spain 2 Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, Sevilla, Spain The proportion of linoleic acid in oilseeds is strongly modified during embryo development by environmental conditions, mainly temperature, producing oils with a final composition that depends on the year and geographical area. The enzyme responsible for the synthesis of linoleic acid from oleic acid is the microsomal oleate desaturase (FAD2). In sunflower, three different FAD2 genes have been isolated and characterized. The FAD2-1 gene encodes the major and seed-specific isoform, whereas FAD2-2 and FAD2-3 are weakly expressed in seeds. We have reported two mechanisms by which temperature regulates the FAD2 activity in sunflower seeds: i) a direct, slow and non-reversible effect, due to the low thermal stability of the FAD2-1 isoform and the repression of the FAD2-1 gene at high temperature and ii) an indirect, fast and reversible effect by which temperature acts on the availability of oxygen, that, in turn, regulates the FAD2 activity. In order to elucidate the mechanism of this second effect, we have investigated this phenomenon at the tissue level by in situ hybridization using FAD2 gene-specific probes labeled with a fluorescent nucleotide. These experiments showed localization of FAD2-1 transcripts in all cell types of the sunflower seed. However, in longitudinal sections of the seed a higher hybridization signal was detected in the procambial ring and the radicle, whereas in transversal sections a preferential accumulation was observed in the palisade parenchima compared to the spongy parenchima. In contrast, FAD2-2 and FAD2-3 transcripts were evenly distributed throughout the seed. This pattern of expression will be discussed in relation to the oxygen concentration inside the sunflower seed.
P14 Phospholipid turnover in the plasma membrane of phosphate limited oat (Avena sativa) Henrik Tjellström, Mats X. Andersson, Karin E. Larsson, R. Henrik Nilsson and Anna Stina Sandelius As much as one third of all organically bound phosphate in the plant cell is associated with phosphate-containing membrane lipids. We have shown that oat grown under phosphate-limited conditions replaced up to 70% of the plasma membrane and the tonoplast phospholipids with non-phosphorous lipids, especially the galactolipid digalactosyl diacylglycerol (DGDG). The phospholipid-to-DGDG exchange appears to be a general phosphate-saving feature of angiosperms. In parallel to the phospholipid replacement, phosphate-limited growth condition also led to enhanced phospholipase activities in the oat plasma membranes: a Ca 2+ -independent phospholipase D (PLD) as well as a phosphatidic acid phosphatase (PAP) were induced. Native gel electrophoresis of oat plasma membranes revealed that both the PLD and the PAP activities co-migrated with a native protein size probably exceeding 100 kD. Three candidate polypeptides for the lipases were identified by mass spectrometry. However, one of the three candidates was previously described as a phosphate-deficiency induced phospholipase C (PLC) in Arabidopsis. A phylogenetic analysis did not reveal any preferential relation to a PLC or a PLD for any of the polypeptides. The in vivo significance of the phospholipid turnover in phosphate-limited oat is presently investigated.
Page 1 and 2: Wednesday 17 August 2005 17:00-20:0
Page 3 and 4: Session G 14:00-14:30 The role of s
Page 5 and 6: Characterisation of sterol carrier
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: Very Long Chain Fatty Acids in sunf
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: Euro Fed Lipid Congress Calendar Fo

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