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KMID : 0903619970380010043
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Journal of the Korean Society for Horticultural Science
1997 Volume.38 No. 1 p.43 ~ p.46
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Fatty Acid Unsaturation of Membrane and Linoleate Desaturase Gene Expression During Root Acclimation to Chilling Temperature in Canola (Brassica napus L)
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A. H. Markhart Ⅲ
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Abstract
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The ability of plants to acclimate to fluctuations in temperature is critical to species fitness and productivity. The present paper is focused on the ability of the root system to acclimate in a chillingtolerant species of canola (Brassica napus L.). The root growth, fatty acid composition, and mRNA levels from a fatty acid desaturase gene (fad3) were measured after the temperature decrease of 25C to 10C and were compared with the overall growth adjustment of whole plants at 25C. Canola root systems rapidly acclimated to the decreased temperature. Root growth stopped immediately when the root temperature was dropped from 25C to 10C. The root growth recovered to about 50% of the growth rates at 25C within 36 hours. Water flux through the root system decreased due to the temperature decrease, however, began to recover within 4 hours. Increased fatty acid unsaturation was measurable in canola roots after the root temperature was lowered to 10C. The ratio of fatty acid unsaturation in intracellular membranes was higher than those of plasma membranes during cold acclimation. Correlated with these growth and physiological changes was an increase in fatty acid unsaturation and an increase in steady-state level of mRNA from the fad3 gene, that codes for the desaturase Chat converts linoleic acid to linolenic acid. The results suggest that root system acclimation to chilling temperature is a rapid process and that an important response is an increase in fatty acid unsaturation that is due to an upregulation of the fad3 fatty acid desaturase gene.
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