Induction of salicylic acid (SA) on transcriptional expression of eight carotenoid genes and astaxanthin accumulation in Haematococcus pluvialis

The green alga Haematococcus pluvialis can produce large amounts of pink carotenoid astaxanthin which is a high value ketocarotenoid. In our study, transcriptional expression patterns of eight carotenoid genes in H. pluvialis in response to SA were measured using qRT-PCR. Results indicated that both 25 and 50 mg/L salicylic acid (SA) could increase astaxanthin productivity and enhance transcriptional expression of eight carotenoid genes in H. pluvialis. But these genes exhibited different expression profiles. Moreover, SA25 (25 mg/L SA) induction had a greater effect on the transcriptional expression of ipi-1, psy, pds, crtR-B and lyc (more than 6-fold up-regulation) than on ipi-2, bkt and crtO, but SA50 (50 mg/L SA) treatment had a greater impact on the transcriptional expression of ipi-1, ipi-2, pds, crtR-B and lyc than on psy, bkt and crtO. Furthermore, astaxanthin biosynthesis under SA was up-regulated mainly by ipi-1, ipi-2, psy, crtR-B, bkt and crtO at transcriptional level, lyc at post-transcriptional level and pds at both levels. Summarily, these results suggest that SA constitute molecular signals in the network of astaxanthin biosynthesis. Induction of astaxanthin accumulation by SA without any other stimuli presents an attractive application potential in astaxanthin production with H. pluvialis.