## 2 Results
### DEGs Associated with the Blue Light Receptors  
Plants utilize photoreceptors to regulate growth and development under light of different wavelengths. Both cryptochrome (CRY) and phototropin (PHOT) are blue light receptors, with conserved signal transduction in different plants. Members of eukaryotic CRYs include plant CRYs (pCRY), animal CRYs (aCRY), and _Drosophila_, _Arabidopsis_, _Synechocystis_, and Human (DASH) CRYs (dashCRY) [46; 47]. Four CRYs (i.e., one pCRY, one aCRY, and two dashCRYs) were identified in _C. reinhardtii_[48] and seven CRYs (i.e., one pCRY, one aCRY, and five dashCRYs) were found in _Volox carteri_[49]. The gene encoding pCRY contains multiple copies in higher plants but a single copy in eukaryotic green algae. To investigate the molecular mechanism regulating the astaxanthin accumulation in response to the blue LED, the CRYs were chosen for further transcriptomic analysis. In our study, seven CRYs were identified in _H. pluvialis_ (Table 1). As the exposure time of blue light increased, the expression levels of genes encoding dashCRYs and CRYs were significantly decreased on day 2 and day 7 compared with those of day 0. Two genes encoding PHOT showed different expression patterns, with one showing no significant change and the other significantly down-regulated. The expression of one gene encoding dashCRY was significantly decreased from day 2 to day 7. On day 7 of the treatment with blue light exposure, the expression levels of genes encoding all blue light receptors were decreased compared with those of white light exposure. No significant changes in the expression of the genes encoding dashCRYs were observed with the addition of SA.  
Figure 10: Expression profiles of proteins (i.e., APX, CAT, ferritin, GPX, GRX, MDAR, PRDX, and SOD) involved in the generation of ROS revealed in the pairwise comparisons of _Haematococcus pluvialis_ based on proteomic analysis. *—indicates significant up-regulation (\(p<0.05\) and FC \(\geq 1.5\)) or significant down-regulation (\(p<0.05\) and FC \(\leq 0.67\)).  
Figure 11: Expression profiles of genes _bcsA_, _bcsZ_, and _Cals_ (**A**) and proteins BcsZ and CalS (**B**) involved in the cell wall biosynthesis revealed in the pairwise comparisons of _Haematococcus plurialis_ based on transcriptomic and proteomic analyses, respectively. *—indicates significant up-regulation (\(p<0.05\) and Log2 FC \(\geq 1\); \(p<0.05\) and FC \(\geq 1.5\)) or significant down-regulation (\(p<0.05\) and Log2 FC \(\leq-1\); \(p<0.05\) and FC \(\leq 0.67\)).  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Class**} & \multirow{2}{*}{**Unigene ID**} & **B02 vs.** & **B07 vs.** & **B02 vs.** & **B07 vs.** & **B07 vs.** & **B252 vs.** & **B257 vs.** \\  & & **W02** & **W07** & **N** & **B02** & **N** & **B02** & **B07** \\ \hline dashCRY & N40695\_c3\_g2 & \(-0.47\) & \(-0.12\) & \(-0.54\) & \(-0.39\) & \(-0.70\) & \(-0.17\) & \(0.38\) \\ dashCRY & N43038\_c0\_g10 & \(-0.74\) & \(-0.49\) & \(-1.48\) & \(-0.09\) & \(-1.34\) & \(0.48\) & \(0.45\) \\ dashCRY & N49636\_c1\_g1 & \(0.35\) & \(-0.33\) & \(-4.15\) & \(-1.54\) & \(-5.46\) & \(0.03\) & \(1.01\) \\ PHOT & N44442\_c1\_g2 & \(-0.15\) & \(-0.03\) & \(0.32\) & \(-0.48\) & \(0.07\) & \(0.30\) & \(-0.12\) \\ PHOT & N50230\_c0\_g1 & \(-0.32\) & \(-0.34\) & \(-0.93\) & \(-0.68\) & \(-1.38\) & \(0.14\) & \(0.02\) \\ CRY & N44179\_c1\_g4 & \(0.00\) & \(-0.41\) & \(-1.40\) & \(-0.65\) & \(-1.83\) & \(0.16\) & \(-0.03\) \\ CRY & N50367\_c0\_g2 & \(0.21\) & \(-0.11\) & \(-1.58\) & \(-0.97\) & \(-2.33\) & \(-0.20\) & \(0.06\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Expression of genes encoding three classes of blue light receptors identified in different pairwise comparisons of _Haematococcus plurialis_.