Heterologous expression of AtLEC1 and AtLEC1-LIKE transcription factors redirects carbon flux toward lipid accumulation in diatom.

backgroundMicroalgal biodiesel is a key fossil fuel alternative, but enhancing lipid accumulation via single metabolic gene overexpression is often ineffective. Transcription factor engineering overcomes this by coordinating multiple metabolic pathways. To address the unexplored role of LEC1-type transcription factors in diatoms, we engineered the euryhaline and psychrotolerant biodiesel candidate diatom Phaeodactylum tricornutum through heterologous expression of the key plant lipid regulators AtLEC1 and AtL1L.

resultsCodon-optimized genes driven by the endogenous fcpA promoter were integrated into the nuclear genome, with regulators localization confirmed in the nucleus. Crucially, AtL1L transformants exhibited significant redirection of carbon flux from carbohydrates toward lipids, evidenced by lipid content increasing to 29.8%-33.9% of dry weight compared to 20.9% in wild-type controls while carbohydrates decreased to 13.3%-16.5% from 23.1%. AtL1L transformants accumulated 42-64% more neutral lipids and 48-68% higher total fatty acids without compromising biomass yield or photosynthetic efficiency (Fv/Fm). Molecular analyses revealed coordinated upregulation of key lipogenic, glycolytic and pyruvate metabolism genes such as acetyl-CoA carboxylase, pyruvate kinase and malic enzyme, which were corroborated by significant increases in corresponding enzyme activities and NADPH levels. Metabolite profiling confirmed accumulation of lipid precursors including acetyl-CoA (1.7-fold elevation) concurrent with reduction of sugars like glucose to less than 39% of wild-type levels.

conclusionsThis study demonstrates the first functional transfer of plant transcription factors to diatoms, providing a transformative strategy for high-productivity microalgal biodiesel.