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Title: LIPID COMPOSITION OF CHLORARACHNIOPHYTES (CHLORARACHNIOPHYCEAE) II: UNUSUAL POLAR LIPIDS AND THE ROLE OF THE NUCLEOMORPH IN STEROL BIOSYNTHESIS

Author
item DAHMEN, JEREMY - MIDDLE TN ST UNIV
item LEBLOND, JEFFREY - MIDDLE TN ST UNIV
item SEIPELT, REBECCA - MIDDLE TN ST UNIV
item ELROD-ERICKSON, MATTHEW - MIDDLE TN ST UNIV
item CAHOON, A. BRUCE - MIDDLE TN ST UNIV
item KINCAID, RODNEY - MIDDLE TN ST UNIV
item Evens, Terence
item CHAPMAN, PETER - USEPA

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/20/2004
Publication Date: 8/8/2004
Citation: Dahmen, J.L., Leblond, J.D., Seipelt, R.L.,Elrod-Erickson, M.J., Cahoon, A., Kincaid,R., Evens, T.J., Chapman, P.J. 2005. Lipid composition of chlorarachniophytes (chlorarachniophyceae) ii: unusual polar lipids and the role of the nucleomorph in sterol biosynthesis. Meeting Abstract.

Interpretive Summary:

Technical Abstract: An initial effort to characterize the fatty acid and sterol composition of the representative chlorarachniophytes, Bigelowiella natans, Gymnochlora stellata, Lotharella amoeboformis, and a Lotharella sp., has shown that their chloroplast glycolipid-associated fatty acids were found to be derived from the common algal/plant lipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). These fatty acids were found to be of limited composition, containing principally eicosapentaenoic acid [20:5(n-3)] and hexadecanoic acid (16:0). Unlike many eukarytic algae, the cytoplasmic membrane lipid fraction was found to be dominated by a number of polar quaternary ammonium-containing lipids that did not contain phosphorus. The fatty acid composition of these polar lipids was both distinct and more variable than the glycolipids, with the fatty acids, 16:0 and docosapentaenoic acid [22:5(n-3)], dominant along with a number of minor C18 and C20 fatty acids. Only two sterols made up the free sterol fraction in all organisms. These were identified as 24-ethylcholesta-5,22E-dien-3ß-ol (70-95%) and 24-methylcholesta-5,22E- dien-3ß-ol (5-30%), with undefined C-24 stereochemistry. Several genes encoding activities required for synthesis of these sterols were computationally identified in B. natans. One sterol biosynthesis gene within this metabolic pathway showed the greatest similarity, by far, to SMT1 of the green alga, Chlamydomonas reinhardtii. However, genes homologues to other species, mostly green plant species, were also found. Further, the method of identification suggested that the sequences have been transferred to a genetic compartment other than the likely original location, the nucleomorph nucleus.