Secondary carotenoid accumulation in flagellates of the green alga Haematococcus lacustris

The combination of nitrogen deprivation and increased cultivation light intensity resulted in the synthesis of secondary carotenoids in flagellates of Haematococcus lacustris. The pigment pattern was characterized by high-pressure liquid chromatography analysis during the accumulation period and in response to inhibitors of carotenoid biosynthesis (diphenylamine, norflurazon and tetcyclacis). Diphenylamine treatment resulted in (i) a decrease in ketocarotenoids and (ii) an accumulation of beta-carotene and zeaxanthin due to inhibition of the beta-carotene oxygenase. Our results indicate that astaxanthin synthesis in H. lacustris follows the biosynthetic pathway elucidated in the marine bacterium Agrobacterium aurantiacum.