An increase in the membrane lipids recycling by PDAT overexpression stimulates the accumulation of triacylglycerol in Nannochloropsis gaditana

Oleaginous microalgae represent potential feedstocks for the sustainable production of lipids thanks to their ability to accumulate triacylglycerols (TAGs). TAG accumulation in several algal species is strongly induced under specific conditions such as nutrient deprivation and high light which, however, also negatively impact growth. Genetic modification of lipogenic pathways can potentially enhance TAG accumulation without nega-tively affecting growth, avoiding the trade-off between biomass and lipid productivity.In this study, the phospholipid: diacylglycerol acyltransferase (PDAT), an enzyme involved in membrane lipid recycling, was overexpressed in the seawater alga Nannochloropsis gaditana. PDAT overexpression induced increased TAG content in actively growing algae cultures while no effects were observed in conditions naturally stimulating strong lipid accumulation such as high light and nitrogen starvation. The increase of TAG content was confirmed also in a strain cultivated in industrially relevant conditions even though PDAT overexpression, if too strong, the gene overexpression becomes detrimental for growth in the longer term. Results overall suggest that genetic modulation of the PDAT gene represents a promising strategy to increase microalgae lipid content by minimizing negative effects on biomass productivity.

Automated summary

Oleaginous microalgae have the potential to be used as sustainable feedstocks for lipid production. This study focuses on the overexpression of the phospholipid: diacylglycerol acyltransferase (PDAT) gene in the seawater alga Nannochloropsis gaditana. The overexpression of PDAT led to increased TAG content in actively growing algae cultures but had no effect under conditions that naturally stimulate lipid accumulation. Results suggest that genetic modulation of the PDAT gene can be a promising strategy to increase lipid content in microalgae without negatively affecting biomass productivity.