Effects of Abscisic acid (ABA) carotenogenesis expression and astaxanthin accumulation in Haematococcus pluvialis

Haematococcus pluvialis is a commercially promising source because of its ability to accumulate astaxanthin up to 4% (w/w) of dry weight under stress conditions. In this study, transcriptional expression pattern of eight carotenoid genes involved in astaxanthin biosynthesis under ABA (25 and 50mg/L) induction was investigated using qRT-PCR. Results showed that except for bkt, almost all genes were up-regulated by ABA with different expression profiles. ABA25 induction had a greater effect on the transcriptional expression level of ipi-1, ipi-2, lyc and crtR-B than on psy, pds and bkt. ABA50 treatment had a greater impact on the transcriptional expression of ipi-1, ipi-2 and crtR-B than on pds, lyc, bkt and crtO. Moreover, astaxanthin biosynthesis under ABA induction might be up-regulated by ipi-1, ipi-2, pds at transcriptional level; lyc performed at both transcriptional and post-transcriptional levels and crtR-b functioned at post-transcriptional levels. Furthermore, there seemed to be little effect on crtO transcriptional expression in ABA25 treatment and on psy mRNA expression in ABA50 treatment and both ABA treatments had no impact on mRNA expression of bkt.