Transcriptome analysis reveals pathways responsible for the promoting effect of sucrose on astaxanthin accumulation in Haematococcus pluvialis under high light condition

Haematococcus pluvialis accumulates large amount of astaxanthin, a valuable ketocarotenoid with super antioxidant activity, under stress conditions. Providing suitable carbon source has been proved to be an effective method to promote astaxanthin accumulation in H. pluvialis, however, mechanisms remain obscure. Here, we demonstrate that adding sucrose (1-10 mM) into the culture media increase astaxanthin yield by 27.9-34.2% in H. pluvialis under high light stress. Subsequently, comparative transcriptomic analysis revealed the mechanism underling the promoting effect of sucrose on astaxanthin biosynthesis. Sucrose treatment significantly upregulated the expression of many enzyme encoding genes involved in sucrose and starch metabolism, glycolysis, astaxanthin biosynthesis, and fatty acids metabolism. In addition, sucrose treatment significantly changed the expression of 29 transcriptional factors, potential key regulators in sucrose metabolism, lipid biosynthesis and astaxanthin biosynthesis. Furthermore, exogenous application of metabolites involved in sucrose catabolism and glycolysis pathway (glucose-6-phosphate disodium and fructose-1,6-diphosphate trisodium) significantly promoted astaxanthin yield by 33.1% and 18.1%, respectively. Our results indicated that sucrose treatment exerts remarkable effects on the transcriptomes of H. pluvialis, favoring the shift from carbon metabolism to astaxanthin accumulation under high light condition.

Automated summary

The addition of sucrose in Haematococcus pluvialis significantly increases astaxanthin accumulation, by upregulating genes involved in sucrose and starch metabolism, glycolysis, astaxanthin biosynthesis, and fatty acids metabolism. This study demonstrates the potential of sucrose treatment in promoting astaxanthin biosynthesis and shifting carbon metabolism towards astaxanthin accumulation in H. pluvialis under high light stress conditions.