The biosynthesis of ether lipids and wax esters requires as precursors fatty alcohols, which are synthesized by Fatty Acyl Reductases (FARs). The presence of ether glycerolipids as well as branched wax esters has been reported in several free-living ciliate protozoa. In the genome of Tetrahymena thermophila, the only ORF sharing similarities with FARs is fused to an acyltransferase-like domain, whereas in most other organisms FARs are monofunctional proteins of similar size and domain structure. Here, we used heterologous expression in plant and yeast to functionally characterize the activities catalyzed by this protozoan protein. Transient expression in tobacco epidermis of a truncated form fused to the green ... More
The biosynthesis of ether lipids and wax esters requires as precursors fatty alcohols, which are synthesized by Fatty Acyl Reductases (FARs). The presence of ether glycerolipids as well as branched wax esters has been reported in several free-living ciliate protozoa. In the genome of Tetrahymena thermophila, the only ORF sharing similarities with FARs is fused to an acyltransferase-like domain, whereas in most other organisms FARs are monofunctional proteins of similar size and domain structure. Here, we used heterologous expression in plant and yeast to functionally characterize the activities catalyzed by this protozoan protein. Transient expression in tobacco epidermis of a truncated form fused to the green fluorescence protein followed by confocal microscopy analysis suggested peroxisomal localization. In vivo approaches conducted in yeast indicated that the N-terminal FAR-like domain produced both 16:0 and 18:0-fatty alcohols, while the C-terminal acyltransferase-like domain was able to rescue the lethal phenotype of the yeast double mutant gat1Δ gat2Δ. Using in vitro approaches, we further demonstrated that this domain is a DiHydroxyAcetone Phosphate Acyl-Transferase (DHAPAT) that uses preferentially 16:0-Coenzyme A as acyl donor. Finally, coexpression in yeast with the Alkyl-Dihydroxyacetone-Phosphate Synthase (ADPS) from T. thermophila resulted in detecting various glycerolipids with an ether bond, indicating reconstitution of the ether lipid biosynthetic pathway. Altogether, these results demonstrate that this FAR-like protein is peroxisomal and bifunctional, providing both substrates required by ADPS to initiate ether lipid biosynthesis.
