Oleate desaturation and acyl turnover in sunflower (Helianthus annuus L.) seed lipids during rapid temperature adaptation |
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Authors: | Cristina Sarmiento Rafael Garcés Manuel Mancha |
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Institution: | (1) Instituto de la Grasa (CSIC), Apartado 1078, E-41080 Sevilla, Spain, ES |
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Abstract: | In-vivo experiments with developing sunflower (Helianthus annuus L.) seeds demonstrated that oleate desaturase activity was stimulated by low temperature (10 °C), repressed by high temperature
(30 °C) and rapidly restored by returning the seeds to low temperature. Within time periods of 2–4 h, in which the de-novo
fatty acid synthesis was negligible, the percentages of oleate (18:1) and linoleate (18:2) were modified in the seed lipids
as a consequence of temperature adaptation. When the seeds were transferred to low temperature, the 18:2 content increased
in all lipids from both microsomal membranes and oil bodies. After shifting to high temperature, the overall 18:2 content
remained constant, but the 18:2 content decreased in diacylglycerols, phosphatidylcholine (PC) and other polar lipids of the
two fractions and also in triacylglycerols (TAGs) of the microsomes but increased in TAGs of the oil bodies. The results indicate
that the mechanism for the rapid adaptation of sunflower seeds to temperature changes involves (i) the synthesis or activation
of oleate desaturase at low temperature and the reversible inhibition of this enzyme at high temperature and (ii) the exchange
of 18:1 and 18:2 between TAGs and PC. Under both low and high temperature, 18:1 is transferred from reserve TAGs to PC and
18:2 is transferred from PC to reserve TAGs. At low temperature, 18:1 is desaturated to 18:2 thus allowing the enrichment
of membrane lipids with 18:2, the excess being stored in reserve TAGs. At high temperature, however, and provided that oleate
desaturase is repressed, the membrane lipids become enriched in 18:1 and the oil-body TAGs become enriched in 18:2.
Received: 11 August 1997 / Accepted: 10 November 1997 |
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Keywords: | :Helianthus (seed) Microsome Oil body Oleate desaturase Temperature adaptation Triacylglycerol |
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