Robert Christopher Brown

Lipid production in Nannochloropsis gaditana is doubled by decreasing expression of a single transcriptional regulator

Lipid production in the industrial microalga Nannochloropsis gaditana exceeds that of model algal species and can be maximized by nutrient starvation in batch culture. However, starvation halts growth, thereby decreasing productivity. Efforts to engineer N. gaditana strains that can accumulate biomass and overproduce lipids have previously met with little success. We identified 20 transcription factors as putative negative regulators of lipid production by using RNA-seq analysis of N. gaditana during nitrogen deprivation. Application of a CRISPR–Cas9 reverse-genetics pipeline enabled insertional mutagenesis of 18 of these 20 transcription factors. Knocking out a homolog of fungal Zn(II)2Cys6-encoding genes improved partitioning of total carbon to lipids from 20% (wild type) to 40–55% (mutant) in nutrient-replete conditions. Knockout mutants grew poorly, but attenuation of Zn(II)2Cys6 expression yielded strains producing twice as much lipid (∼5.0 g m−2 d−1) as that in the wild type (∼2.5 g m−2 d−1) under semicontinuous growth conditions and had little effect on growth.

Complete Genome Sequence of the Model Oleaginous Alga Nannochloropsis gaditana CCMP1894

ABSTRACT The model oleaginous alga Nannochloropsis gaditana was completely sequenced using a combination of optical mapping and next-generation sequencing technologies to generate one of the most complete eukaryotic genomes published to date. The assembled genome is 30.7 Mb long.