Exploring a blue-light-sensing transcription factor to double the peak productivity of oil in Nannochloropsis oceanica.

Oleaginous microalgae can produce triacylglycerol (TAG) under stress, yet the underlying mechanism remains largely unknown. Here, we show that, in Nannochloropsis oceanica, a bZIP-family regulator NobZIP77 represses the transcription of a type-2 diacylgycerol acyltransferase encoding gene NoDGAT2B under nitrogen-repletion (N+), while nitrogen-depletion (N-) relieves such inhibition and activates NoDGAT2B expression and synthesis of TAG preferably from C16:1. Intriguingly, NobZIP77 is a sensor of blue light (BL), which reduces binding of NobZIP77 to the NoDGAT2B-promoter, unleashes NoDGAT2B and elevates TAG under N-. Under N+ and white light, NobZIP77 knockout fully preserves cell growth rate and nearly triples TAG productivity. Moreover, exposing the NobZIP77-knockout line to BL under N- can double the peak productivity of TAG. These results underscore the potential of coupling light quality to oil synthesis in feedstock or bioprocess development.