Microsomal Phospholipid Molecular Species Alterations during Low Temperature Acclimation in Dunaliella

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Abstract
A detailed analysis of the low temperature-induced alterations of D. salina (UTEX 1644) microsomal membrane lipids was carried out. Microsomal membranes were isolated from cells grown at 30.degree. C, from cells shifted to 12.degree. C for 12 h, and from cells acclimated to 12.degree. C. Fatty acid analyses of the major lipid classes demonstrated significant changes in the fatty acid composition of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) but not phosphatidylcholine (PC) during the initial 12 h at low temperature. These changes did not entail enhanced desaturation of linoleic acid. Subsequent to 12 h, the proportions of linolenic acid increased in all phospholipids. Molecular species analyses of the phospholipids demonstrated that the most immediate changes following a shift to low temperature were limited to several molecular species of PE and PG. The changes observed in PE included a decrease in C30 species and concomitant increases in C34 and C36 species. Compositional changes associated with PG entailed the emergence of a new molecular species (18:1/18:1) not found at 30.degree. C. The retailoring of molecular species resulted in an increase in the number of species having 2 unsaturated acyl chains and did not reflect a simple enhancement of desaturase activity as suggested by the fatty acid analysis. The initial alterations in response to low temperature stress involve discrete changes in certain molecular species. These and further alterations of molecular species following acclimation to low temperature apparently augment increases in acyl chain desaturation as a means of modifying membrane properties in response to low temperature stress.

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