Biosynthesis of Polyunsatiirated Fatty Acids in Zooxanthellae and Polyps of Corals

摘要

The fatty acid (FA) composition of zooxanthellae, polyp tissue, and intact colonies was determined in soft coral Sinularia sp. and hard coral Acropora sp. Analysis of the distribution of polyunsaturated fatty acids (PUFAs) among the zooxanthellae and the host organism showed that 18 : 3n-6 and C_(18_22) PUFAs of the n-3 series (18 : 4n-3, 20 : 5n-3, 22 : 5n-3, and 22 : 6n-3) were mainly synthesized by the zooxanthellae and that C_(20-22) PUFAs of the n-6 series (20 : 3n-6, 20 : 4n-6, and 22 : An-6) were synthesized in the polyp tissue. Soft coral polyps were able to synthesize tetracosapolyenoic FAs (24 : 5n-6 and 24 : 6n-3) and 18 : 2n-7, their zooxanthellae synthesized C_(16) PUFAs (16 : 2n-7, 16 : 3n-4, and 16 : 4n-l). It is supposed that the biosynthesis of 16 : 2n-7 in Sinularia sp. and 18 : 3n-6 in Acropora sp. is catalyzed by A6 desaturase. The relatively even distribution of three FAs (18 :2n-6, 18: 3n-6, and 16 : 2n-7)amonglipids of zooxanthellae and coral polyps indicates the possible transport of these FAs between symbionts and the host organism.