INSIGHTS INTO LIPID PRODUCTION IN THE GREEN ALGAL CHLOROPLAST: STUDY OF A DIACYLGYCEROL TRANSFERASE AND TWO PHYTYL ESTER SYNTHASES FROM CHLAMYDOMONAS REINHARDTII

CARRO, M.M.; SOTO, D.; GONORAZKY, G.; BAGNATO, C; MAMONE, L.; STRUGO, N.; DI FINO, L.; BELIGNI, MV

Ciudad Autónoma de Buenos Aires

Congreso; Reunión conjunta SAIB-SAMIGE 2020; 2020

SAIB-SAMIGE

Eukaryotic microalgae are important producers of triacylglycerides (TAGs). TAGs are used for different technological applications, such as biofuel or biopolymer production. Distinct stress conditions induce TAG accumulation in microalgae. One of them is nitrogen deprivation, which is the most employed in the biofuel industry. Nevertheless, this growth condition diminishes cellular division and, hence, negatively impacts total lipid production. Until now, most biochemical studies have focused on enzymes that play a role in the conventional cytosolic/microsomal TAG synthesis pathway. In order to advance in the knowledge of lipid metabolism in microalgae, we performed a computational analysis designed to detect novel enzymes involved in TAG synthesis. We identified a diacylglycerol transferase 3 (DGAT3) and two phytyl ester synthases (PESα y PESβ) in Chlamydomonas reinhardtii, which are distant homologues of DGAT3 and PES from plants, respectively. DGAT3 is a soluble enzyme that produces TAGs from diacylglycerol (DAG) acylation. Several pieces of evidence suggest that C. reinhardtii DGAT3 is imported to the chloroplast and its accumulation is induced by light. Plant PES are nonspecific enzymes. They play a role in chlorophyll degradation via the acylation of phytol, a chlorophyll degradation byproduct. PES also acylate DAG to produce TAG. Computational analysis of C. reinhardtii PES suggest that these enzymes have no transmembrane domains, are localized to the chloroplast, and their expression is induced by light. These results suggest the existence of TAG biosynthetic pathways in the chloroplast of green algae.