Elongation capacity of polyunsaturated fatty acids in the annelid Platynereis dumerilii

In animals, elongation of very long-chain fatty acid (Elovl) proteins play pivotal functions in the biosynthesis of fatty acids, including the physiologically essential long-chain polyunsaturated fatty acids (LC-PUFA). Polychaetes have important roles in marine ecosystems, contributing not only to nutrient recycling but also exhibiting a distinctive capacity for biosynthesising LC-PUFA, as emphasised in previous research. In order to expand our current understanding of the LC-PUFA biosynthesis in polychaetes, the present study conducted a thorough molecular and functional characterisation of Elovl occurring in the model organism Platynereis dumerilii. In this study, we identify six Elovl proteins in the genome of P. dumerilii. The sequence and phylogenetic analyses established that four Elovl, identified as Elovl2/5, Elovl4 (two genes) and Elovl1/7, have putative functions in the LC-PUFA biosynthesis. Functional characterisation in yeast confirmed the roles of these elongases in the LC-PUFA biosynthetic pathways, demonstrating that P. dumerilii possesses a varied and functionally diverse complement of Elovl enzymes that, along the enzymatic specificities of previously characterised desaturases, enable P. dumerilii to perform all the reactions required for the biosynthesis of the LC-PUFA. Importantly, we uncovered that one of the two Elovl4-encoding genes from P. dumerilii is remarkably long in comparison with any other animals Elovl, which contains a C terminal KH domain unique among Elovl enzymes. The distinctive expression pattern of this protein in photoreceptors strongly suggests a central role in vision.