Heterologous expression of a yeast lipid transporter promotes accumulation of storage compounds in Chlamydomonas

Microalgae offer renewable and sustainable sources for the bioindustrial production of nextgeneration biofuels and biomaterials. In this work, we heterologously expressed a lipid transporter gene (MMF1) from the major facilitator superfamily in the model green microalga Chlamydomonas reinhardtii, under the influence of a strong light and temperature-inducible promoter. The full-length cDNA sequence of MMF1 from Moesziomyces antarcticus T-34 (MaMMF1) encodes for a 542 amino acid polypeptide with transmembrane efflux pump activity. M. antarcticus is a fungus that can produce and secrete large amounts of glycolipid biosurfactants known as mannosylerythritol lipids (MELs) under nitrogen starvation conditions. Heterologous expression of MaMMF1 in C. reinhardtii resulted in a slight increase in cell biomass, with mutants exhibiting on average about 1.8-fold larger cell sizes. Total lipid content almost doubled in cells expressing MaMMF1 relative to the control strain when cultures were grown for two days under nitrogen starvation. Moreover, average starch content was over 2-fold higher in the mutants. Our results showed that algal strains engineered with the MaMMF1 MEL transporter were capable of possibly redirecting the carbon flux, which resulted in improved growth and accumulation of high-value storage compounds.