Abstract
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.
Highlights
Astaxanthin is a red carotenoid pigment with a high commercial value that has attracted considerable attention for its biological properties, such as its antioxidant, anti-inflammatory, and anti-cancer activities, as well as its coloring for fish (Fujii 2015)
Given that NaAc is an important inducer of astaxanthin synthesis, we focus on its effects on the transcriptional levels of 5 key genes involved in astaxanthin synthesis — crtw, crtz, psy, pds, and lcyB — to provide a foundation for furthering our understanding of the mechanisms underlying astaxanthin synthesis
The primers used for amplification of crtz, crtw, psy, pds, and lcyB were all synthesized (Sangon)
Summary
Astaxanthin is a red carotenoid pigment with a high commercial value that has attracted considerable attention for its biological properties, such as its antioxidant, anti-inflammatory, and anti-cancer activities, as well as its coloring for fish (Fujii 2015). Green microalgae are the main natural source of astaxanthin, and provide ideal models for studying the regulation of ketocarotenoid synthesis (Linden 1999, Grünewald et al 2001). When the synthesis of these carotenoids is inhibited, the photosynthesis and growth of plants do not proceed at normal rates (Jackson et al 2008, Poojary et al 2016). Phytoene is an important carotenoid precursor of astaxanthin (Harker & Young 1995), as it is the first carotenoid produced during astaxanthin synthesis. The accumulation of phytoene is closely tied to astaxanthin production. We study the relationship between astaxanthin and phytoene under induction conditions to enhance our understanding of the accumulation process of astaxanthin and identify the most optimal induction conditions for astaxanthin synthesis
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