Heterologous expression of DGAT genes in the marine microalga Tetraselmis chui leads to an increase in TAG content

Abstract

Over recent years, there has been continued interest in investigating microalgae as a sustainable and renewable source of biodiesel, and a handful of studies have been devoted to the metabolic engineering of microalgae focusing on microalgal oil. In this study, we have applied a transformation method previously developed in our laboratory for the green microalga Tetraselmis chui to introduce and overexpress independently two diacylglycerol acyltransferase (DGAT) genes, EpDGAT1 from a plant species of the Boraginaceae family, and ScDGAT2 from Saccharomyces cerevisiae. Hundreds of transformed clones were obtained, but the screening was restricted to 50 clones for each DGAT1 and DGAT2 type. Twelve transformed clones were finally selected for their high total fatty acid content, which were re-cultured and re-analyzed to specifically determine their triacylglycerol (TAG) content. Five clones showed TAG contents notably higher than the wild-type (WT) strain, achieving TAG increases from 40% up to 115% of dry weight (mg g−1). These increases are, to the best of our knowledge, the highest reported in microalgae to date and serve as a proof of concept regarding the possibility of using this technology to markedly improve oil content in microalgae or any other product suitable for genetically engineered enhancement.