Phylogenetic analysis of Fatty Acid Desaturases reveals contrasting evolutionary clues in ciliates

CID N; NUSBLAT AD; M.GUADALUPE MONTES; NUDEL BC; SÁNCHEZ GRANEL L; ELGUERO, ME

Cordoba

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2016

The Integral Membrane Diiron Enzymes (IMDE) are a class ofbinuclear non-heme iron proteins widely distributed amongprokaryotes and eukaryotes. They are characterized by aconserved tripartite motif consisting of eight to ten histidines.Their key function is the activation of the dioxygen moiety toserve as efficient catalysts for reactions of hydroxylation,desaturation or reduction. To date most studies on IMDE werecarried out in metazoan, phototrophic or parasitic organisms,whereas genome-wide analysis in heterotrophic free livingprotozoa, such as the Ciliophora phylum, has not beenundertaken. Our genome wide approach retrieved 118 putativesequences of the IMDE type with large differences in numberamong the ciliates: 11 sequences in Euplotes octocarinatus, 7in Ichthyophthirius multifiliis, 13 in Oxytricha trifallax, 18in Stilonichia lemnae, 25 in Tetrahymena thermophila, 31in Paramecium tetraurelia and 13 in Pseudocohnilembuspersalinus. Interestingly, the analysis of the FA desaturasesfamily showed that the spirotrichs O. trifallax and S.lemnae have no genes that encode for any of these proteins,suggesting that their lipids derive from algae like C.reinhardtii, which is used as foodstuff in cultures. Additionallythe analysis of the lipid content of O. trifallax by GC?MSrevealed a quantitative composition in the ratio ofsaturated/unsaturated fatty acids that was significantlydifferent from the algae, thus indicating re-routing,modification and regulation of precursors not previouslydescribed.