Transcriptome analysis reveals regulation of gene expression during photoacclimation to high irradiance levels in Dunaliella salina (Chlorophyceae)

The unicellular green alga Dunaliella salina is an attractive organism for studying photoacclimation responses. Changes in irradiance level during cell growth affect the organization and structure of the photosystem and the composition of pigments. In this study, D. salina was exposed to different irradiance levels, and cell growth, photosynthetic activity, pigments, and neutral lipids were analyzed. Photosystem II activity and chlorophyll content were reduced, carotenoids content and neutral lipids increased as light intensity increased, suggesting that photosynthetic apparatus was reduced and photoprotection mechanisms were activated. The RNA of D. salina was sequenced to investigate the transcriptomic response of the organism after transitioning from normal light conditions to higher light intensity. Genes encoding for enzymes involved in photosynthesis were downregulated, whereas genes involved in the metabolism of carotenoid and triacylglycerol were upregulated. Genes encoding for photoprotective enzymes related to reactive oxygen species scavenging and to the xanthophyll cycle were also upregulated at higher irradiance levels. The present transcriptomic study would assist in the comprehensive understanding of photoacclimation mechanisms of D. salina.