Chlorophyll as key indicator to evaluate astaxanthin accumulation ability of Haematococcus pluvialis

Background Natural astaxanthin is mainly derived from Haematococcus pluvialis. In the photoinduction phase, astaxanthin accumulation ability can be significantly affected by the characteristics of H. pluvialis cells in the proliferation phase. Based on sequential heterotrophy-dilution-photoinduction (SHDP) technology, the authors' previous study showed that high astaxanthin accumulation ability is accompanied by high chlorophyll content of H. pluvialis heterotrophic cell; whereas the mechanism of this result remained largely obscure. Therefore, transcriptome analysis was conducted to explain this mechanism. Results RNA-seq analysis showed that the transcription level of chlorophyll synthesis-related genes was negatively correlated with genes related to astaxanthin synthesis. A metabolic network between chlorophyll synthesis and astaxanthin accumulation was proposed. Conclusions The relationship between chlorophyll synthesis and astaxanthin accumulation was clarified. Chlorophyll degradation products might be used for astaxanthin synthesis through certain pathways. This study enlightens on the mechanism for the transformation of pigment and is conducive to optimize culture process of H. pluvialis by improving the chlorophyll content of heterotrophic cell.