Day/night variation in fatty acids and lipids biosynthesis in sunflower (Helianthus annuus L.) seeds.

PLEITE RAFAEL; RONDANINI DÉBORAH; GARCÉS RAFAEL; MARTÍNEZ-FORCE ENRIQUE

CROP SCIENCE

The Crop Science Society of America

Lugar: Madison; Año: 2008 vol. 48 p. 1952 - 1957

0011-183X

It is well known that fatty acid biosynthesis in leaves is closely related with photosynthesis; although a residual synthesis is also detected during the night. But it is less known the effect of the day/night cycle in fatty acid biosynthesis in heterotrophic tissues like developing seeds. Through the use of radioactive precursors we have detected variations in the metabolism of fatty acids in lipids during the day/night period in sunflower seeds (Helianthus annuus L.). These oscillations have been observed both in the fatty acids bound to triacylglycerols as well as in polar lipids indicating a fine regulation of the lipids biosynthetic activities in sunflower developing seeds. Additionally, in the triacylglydcerol fraction, periodic variations were observed in the oleic and linoleic acids content as a consequence of qualitative variations in the biosynthetic machinery during the day/night period related with temperature changes. Analyzing the rate of oleic acid desaturation, a significant increase in activity was observed in the middle of the night, indicative of the importance of nocturnal desaturation. Similar variations were also observed in the stearoyl-ACP desaturase activity. Concluding, this study has shown the variation in the lipid biosynthetic capacity in sunflower developind seeds during the day/night cycle, including control over individual enzymes, like the stearoyl-ACP desaturase; and the influence of diurnal and nocturnal temperatures in the quality (oleic/linoleic ratio) of the oil.