Insights into lipid production in the green algal chloroplast: study of a diacylgycerol transferase and two phytyl ester synthases from Chlamydomonas reinhardtii.

SOTO, DÉBORA; MAMONE, LEANDRO; GONORAZKY, GABRIELA; DI FINO, LUCIANO; CARRO, MERCEDES; BAGNATO, CAROLINA; BELIGNI, VERONICA

Ciudad Autónoma de Buenos Aires

Congreso; REUNIÓN CONJUNTA SAIB-SAMIGE | EDICIÓN ON-LINE; 2020

Eukaryotic microalgae are important producers of triacylglycerides (TAGs). TAGs are used for differenttechnological applications, such as biofuel or biopolymer production. Distinct stress conditions induce TAGaccumulation 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 conventionalcytosolic/microsomal TAG synthesis pathway. In order to advance in the knowledge of lipid metabolism inmicroalgae, we performed a computational analysis designed to detect novel enzymes involved in TAG synthesis. Weidentified a diacylglycerol transferase 3 (DGAT3) and two phytyl ester synthases (PESα y PESβ) in Chlamydomonasreinhardtii, which are distant homologues of DGAT3 and PES from plants, respectively. DGAT3 is a soluble enzymethat produces TAGs from diacylglycerol (DAG) acylation. Several pieces of evidence suggest that C. reinhardtiiDGAT3 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. PESalso acylate DAG to produce TAG. Computational analysis of C. reinhardtii PES suggest that these enzymes have notransmembrane domains, are localized to the chloroplast, and their expression is induced by light. These resultssuggest the existence of TAG biosynthetic pathways in the chloroplast of green algae.