The effect of light intensity on the production and accumulation of pigments and fatty acids in Phaeodactylum tricornutum

The diatom Phaeodactylum tricornutum is known to accumulate polyunsaturated fatty acids (PUFAs), especially omega-3 fatty eicosapentaenoic acid (EPA) 20:5n3, which is health beneficial and are essential in human and animal diets. The main genes involved in the biosynthesis of EPA have been reported, but the effect of light and other environmental factors on transcription of such genes is poorly understood. This paper evaluates the transcription of six genes related to EPA production, fatty acid methyl esters (FAMEs), and pigments as a result of growing P. tricornutum under 150 and 750 mu mol photons m(-2) s(-1) irradiance up to 72 h. Regarding transcription levels, all genes displayed a wide variation range in time. Under 24 h of exposure to 750 mu mol photons m(2) s(-1), transcription of PTD6, PTD15, ELO6_b1, and ELO6_b2 significantly increased, whereas 72 h exposure led PTD6 transcript levels to decrease significantly, and PTD5 alpha and ELO6_b1 1 to increase. The 72-h evaluation showed that the 150 mu mol photons m(-2) s(-1) irradiance resulted in a 4-fold increase pigments (chlorophyll and carotenoids) production, as well as in PUFAs (16.59%) production, including EPA (5.72%). Conversely, the 750 mu mol photons m(-2) s(-1) irradiance resulted in increased saturated fatty acids (SFAs) and decreased PUFA concentrations in the FAME distribution. The irradiance variation had a major effect on microalgal metabolism as a result of membranes remodeling, PUFA synthesis rerouting, SFA, and pigments. Such information could be utilized for improving pigments, EPA, and other PUFA syntheses from P. tricornutum.