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Dunaliella salina is a halotolerant marine microalga, known for the accumulation of β-carotene. The BCH-type β- carotene hydroxylase plays a major role in the conversion of β-carotene to xanthophylls. The β-carotene hydroxylase fromthe chlorophycean microalga, Chlamydomonas reinhardtii was amplified, and the sequence alignment analysis showed that the amplified gene belongs to the group of BCH-type hydroxylases. The amplified β-carotene hydroxylase gene with rubisco promoter and chloroplast transit peptide was introduced into the genome of the D. salina by Agrobacterium-mediated genetic transformation. The carotenoid analysis showed a 3-fold increase of violaxanthin at growth stage and a 2-fold increase of zeaxanthin under stress conditions in transformed D. salina.

Phenolic compounds such as vanillin, vanillic acid, gallic acid, coumarin, caffeic acid and acetosyringone, extracted and identified from spent medium of Dunaliella salina has shown to facilitate the virulence (vir) gene induction in Agrobacterium strain A348 (harboring pSM358, a virE::LacZ fusion vector). Among these phenolic compounds, vanillin showed highest concentration of 38.12 ± 0.88 μg L−1 in spent medium. All these phenolic compounds were evaluated independently for induction of vir gene expression using β-galactosidase activity. Our results showed that except for gallic acid, therewas significant vir gene induction activity and these phenolic compounds may be involved in facilitating efficient Agrobacterium-mediated transformation in D. salina.