A new approach to promote astaxanthin accumulation via Na2WO4 in Haematococcus pluvialis

The optimum concentration of Na2WO4 was explored in relation to the cell density and astaxanthin content in Haematococcus pluvialis. Then, the cellular morphology, nitrate reductase (NR) activity, soluble sugar and protein contents, and chlorophyll fluorescence were measured, and the transcriptional expression of carotenogenic genes was determined by quantitative real-time PCR. The results showed that 3.0 mmol/L of Na2WO4 was the optimum concentration to induce astaxanthin accumulation, with a maximum content of 49.41 +/- 0.13 pg/cell reached on the tenth day. The NR activity decreased significantly and continually after Na2WO4 treatment. The soluble sugar content increased gradually during the experimental period and was eventually significantly higher than that in the control. The soluble protein content increased rapidly, reached a maximum in day 0.5 and day 1 and then decreased. The effective photochemical efficiency of PSII (F-v'/F-m') and light saturation (E-k) first decreased and then tended to stabilize, and NADP(-)(+)glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression was correlated with photosynthesis. The transcriptional expression of ipi, psy and bkt was significantly increagod compared with that in the control after application of Na2WO4, and the relative expression of ipi reached the highest level on the fifth day, with a 98.03 +/- 1.92 fold increase. Our results describe a new approach to promote the effective accumulation of astaxanthin in H. pluvialis by NR inhibitor Na2WO4.