title: Temperature-dependent endogenous oxygen concentration regulates microsomal oleate desaturase in developing sunflower seeds.
abstract: Oleoyl-phosphatidylcholine desaturase (FAD2) is a key enzyme involved in fatty acid desaturation in oilseeds, which is affected by environmental temperature. The results of this study show that FAD2 is regulated in vivo via temperature-dependent endogenous oxygen concentrations in developing sunflower (Helianthus annuus L.) seeds. By combining in vivo oxygen profiling, in situ hybridization of FAD2 genes, an assay of energy status, fatty acid analysis, and an in vitro FAD2 enzyme activity assay, it is shown that: (i) the oil-storing embryo is characterized by a very low oxygen level that is developmentally regulated. Oxygen supply is mainly limited by the thin seed coat. (ii) Elevations of external oxygen supply raised the energy status of seed and produced a dramatic increase of the FAD2 enzyme activity as well as the linoleic acid content. (iii) A clear negative correlation exists between temperature and internal oxygen concentration. The changes occurred almost instantly and the effect was fully reversible. The results indicate that the internal oxygen level acts as a key regulator for the activity of the FAD2 enzyme. It is concluded that a major mechanism by which temperature modifies the unsaturation degree of the sunflower oil is through its effect on dissolved oxygen levels in the developing seed.
authors: Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), D-06466 Gatersleben, Germany.
authors: Hardy
authors: H
authors: Rolletschek
authors: Ljudmilla
authors: L
authors: Borisjuk
authors: Alicia
authors: A
authors: Sánchez-García
authors: Cecilia
authors: C
authors: Gotor
authors: Luis C
authors: LC
authors: Romero
authors: José M
authors: JM
authors: Martínez-Rivas
authors: Manuel
authors: M
authors: Mancha
mesh_terms: D044943:Fatty Acid Desaturases / Q000378:metabolism*; D006368:Helianthus / Q000196:embryology*; D017403:In Situ Hybridization; D008861:Microsomes / Q000201:enzymology*; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D012639:Seeds / Q000201:enzymology*; D013696:Temperature
chemical_list: D044943:Fatty Acid Desaturases; C021904:Phosphatidylcholine desaturase; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010100:Oxygen