A premetazoan origin of plasmalogen biosynthesis in animals

COSTA J; GABRIELLI M; ALTABE SG; UTTARO AD

Mendoza

Congreso; LVIII Reunión anual de la SAIB; 2022

Plasmalogens are glycerophospholipids with a vinyl ether bond at sn-1 position, which have unique physical-chemical properties. They are involved in the regulation of membrane functions and in important signaling pathways. Its synthesis evolved first in anaerobic bacteria but did not persist in facultative and aerobic bacteria that appeared after the rise of oxygen in the primitive Earth’s atmosphere. Plasmalogen biosynthesis, now requiring molecular oxygen, later reappeared in animals (vertebrates and invertebrates), some protists and mixobacteria, but not in plants and fungi. The final and key step in plasmalogen synthesis is catalyzed by a 1´alkyl desaturase (PDES1). This, till very recently orphan enzyme, was shown to be encoded by the CarF and TMEM189 genes in mixobacteria and vertebrates, respectively. Capsaspora owczarzaki belongs to the clade Filozoa (Filasterea, Choanoflagellata and Metazoa), and is one of the closest unicellular relatives of animals. Its life cycle alternates between filopodial (adherent), aggregative and cystic stages. In this work we analyzed the fatty acid profile of each stage. This analysis also showed a progressive increase in the content of plasmalogen-derived aldehydes from the filopodial to the cystic stage. We found a highly reliable ortholog of PDES1 in Capsaspora but not in other members of Opisthokonta. A phylogenetic analysis revealed that the Capsaspora desaturase clusters together with TMEM189, indicating a single and unicellular origin for the reappearance of plasmalogen in animals, probably in the common ancestor of Filozoa. The finding of CarF/TMEM189-like desaturases and plasmalogen synthesis in Amoebozoa and Excavata protists should be ascribed to independent acquisition processes. This is the first report of plasmalogens in a non-metazoan Filozoa.