Accumulation of phytoene and astaxanthin and related genes expression in Haematococcus pluvialis under sodium acetate stress

Phytoene and astaxanthin are 2 important carotenoids in the green alga Haematococcus pluvialis. Under environmental stress, the synthesis of phytoene in H. pluvialis increases significantly, and phytoene is converted to astaxanthin through enzymatic catalysis. This paper analyzes the relationship between astaxanthin and phytoene accumulation in carotenoid synthesis pathways under different concentrations of sodium acetate (NaAc) by high-performance liquid chromatography. The highest concentrations of phytoene and astaxanthin were observed at the NaAc concentration of 6 g l−1 on the 12th day of induction. The highest astaxanthin concentration achieved was 2.26 ± 0.28%. Therefore, we concluded that 6 g l−1 NaAc and induction for 12 d provided the optimal inducing conditions for astaxanthin accumulation in H. pluvialis. psy, pds, lcyB, β-carotene ketolase crtw, and crtz, which are genes related to phytoene and astaxanthin synthesis, were cloned and studied at the transcriptional level. crtw and crtz were continuously up-regulated since the first day of induction, while psy, pds, and lcyB were continuously up-regulated starting on the 3rd day of induction. These findings are important for enhancing our understanding of the mechanism of accumulation of phytoene and astaxanthin in H. pluvialis and provide a foundation for identifying the induction conditions necessary for optimizing astaxanthin production and increasing astaxanthin yields.