Enhancement of astaxanthin biosynthesis in Haematococcus pluvialis via inhibition of autophagy by 3-methyladenine under high light

The objective of this study is to characterize effects of autophagy inhibition by 3-methyladenine on astaxanthin and fatty acid accumulation in Haematococcus pluvialis cultivated under high light condition. The present data show that 0.02 mM 3-methyladenine treatment effectively inhibited autophagosome formation but no impact on the cell growth and biomass of H. pluvialis, leading to a large increase in cellular reactive oxygen species (ROS), astaxanthin and fatty acid accumulation as well as palmitic acid enrichment under high light of 700 mu mol.m(-2).s(-1). Furthermore, the key genes such as phytoene synthase (PSY), beta-carotene ketolase (CRTO), and beta-carotene hydroxylase (CRTR-b) in astaxanthin pathway are upregulated significantly whereas the expressions of the lipid-related genes biotin carboxylase (BC) and diacylglycerol acyltransferase (HpDGAT2D) just increased slightly in the 3-methyladenine-treated cells. Astaxanthin accumulation is not perfectly linear with fatty acid biosynthesis in H. pluvialis treated by 3-methyladenine under high light. Overall, autophagy might function importantly in astaxanthin and lipid enrichment in H. pluvialis under stress condition. The findings provide new insights to further investigation on the metabolic regulation in microalgae.