2Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia
3Institute for Cellular and Intracellular Symbiosis, Urals Branch of the Russian Academy of Sciences, 460000 Orenburg, Russia
4National Research Nuclear University “MEPhI”, Center of Humanitarian Studies and Technologies, 115409 Moscow, Russia
* To whom correspondence should be addressed.
Received July 6, 2015; Revision received July 21, 2015
We report on the effects of high light irradiance (480 µmol quanta/(m2·s)) and salinity (160 and 200 g/liter NaCl) on culture growth as well as on cell lipid pigment and fatty acid (FA) composition in three novel strains of halophile microalga from the genus Dunaliella. Based on the ITS1–5.8S rRNA–ITS2 sequence and on the capability of accumulation of secondary (uncoupled from the photosynthetic apparatus) β-carotene, the strains Dunaliella sp. BS1 and BS2 were identified as D. salina and Dunaliella sp. R5 as D. viridis. Under conditions optimal for growth, chlorophylls and primary carotenoids (mainly lutein) dominated the pigment profile of all investigated strains. The main FA were represented by unsaturated C18 FA typical of thylakoid membrane structural lipids. In all studied cells, stressors caused a decline in chlorophylls and an increase in unsaturated C16 and C18 FA associated with reserve lipids. The carotenogenic species D. salina demonstrated 10-fold increase in carotenoids accompanied by a decline in lutein and a drastic increase in β-carotene (up to 75% of total carotenoids). In D. viridis, only 1.5-fold increase in carotenoid content took place, the ratio of major carotenoids remaining essentially unchanged. The role of the carotenogenic response in mechanisms of protection against photooxidative damage is discussed in view of halophile microalgae stress tolerance and application of the new Dunaliella strains for biotechnological production of β-carotene.
KEY WORDS: carotenoids, chlorophylls, fatty acids, molecular identification, photoacclimation, salt tolerance, stress