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.

Effects of High Water Table and Short-Term Flooding on Growth, Yield, and Seed Quality of Sunflower

“…There have been some previous reports about the relationship between the fatty acid composition and environmental conditions. For example, Rolletschek et al (2007) reported about fatty acid composition in developing sunflower seeds, the effect of environmental temperature and the key enzyme involved in fatty acid desaturation. The key enzyme was oleoylphosphatidyl choline desaturase which is responsible for the desaturation of oleic acid into linoleic acid.…”

Environmental effect on sunflower oil quality

“…Oil content and composition are modified by high constant temperature during sunflower grain development, and previous reports indicated a marked reduction in the percentage of linoleic acid in standard sunflower oil, apparently due to the effect of temperature on the activity of the enzyme oleate desaturase, which is responsible for the conversion of oleic to linoleic acid (Flagella et al 2002, Grompone 2005. Garcés and Mancha (1991), who established that the oleyl-phosphatidylcholine-desaturase activity, in sunflower, is inhibited at temperatures above 20 °C, specifically investigated this effect and Rolletschek et al (2007), afterwards, demonstrated the mechanism by which temperature modifies the unsaturation degree of the sunflower oil through its effect on dissolved oxygen levels in the developing seed.…”

Fatty Acid Content of Seed at Different Development Stages in Canola on Different Soil Types with Low Organic Matter

“…The biosynthetic pathways leading to the formation of oil fatty acids have been widely studied in oilseeds, such as sunflower (Helianthus annuus L.) (Garcia-Diaz et al, 2002;Rondanini et al, 2003;Rolletschek et al, 2007;Zlatanov et al, 2009), groundnut (Arachis hypogaea L.) (Hassan et al, 2005b), rapeseed species (Brassica sp.) (Bhardwaj and Hamama, 2003), safflower (Carthamus tinctorius L.) (Rahamatalla et al, 2001) and cuphea (Cuphea sp.)…”