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Browsing by Author "Brenig, Bertram"

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  • Isolation and characterization of a stress-inducible Dunaliella salina Lcy-β gene encoding a functional lycopene β-cyclase
    Publication . Ramos, Ana; Coesel, Sacha; Marques, Ana; Rodrigues, Marta; Baumgartner, Alexandra; Noronha, João; Rauter, Amélia; Brenig, Bertram; Varela, J.
    The halotolerant green alga Dunaliella salina accumulates large amounts of β-carotene when exposed to various stress conditions. Although several studies concerning accumulation and biotechnological production of β-carotene have been published, the molecular basis and regulation of the genes involved in carotenoid biosynthesis in D. salina are still poorly known. In this paper, we report the isolation and regulation of the lycopene β-cyclase (Lcy-β) gene by abiotic stress. The function of this gene was determined by heterologous genetic complementation in E. coli. Gene expression and physiological analyses revealed that D. salina Lcy-β steady-state transcript and carotenoid levels were up-regulated in response to all stress conditions tested (salt, light and nutrient depletion). The results presented here suggest that nutrient availability is a key factor influencing carotenogenesis as well as carotenoid biosynthesis-related gene expression in D. salina.
    2008Journal article Restricted access Show more
  • Molecular and functional characterization of a cDNA encoding 4-hydroxy-3-methylbut-2-enyl diphosphate reductase from Dunaliella salina
    Publication . Ramos, Ana; Marques, A. R.; Rodrigues, M.; Henriques, Nuno; Baumgartner, Alexandra; Castilho, Rita; Brenig, Bertram; Varela, J.
    In green algae,the final step of the plastidial methylerythritol phosphate (MEP) pathway is catalyzed by 4-hydroxy-3-methylbut-2-enyldiphosphate reductase(HDR; EC: 1.17.1.2),an enzyme proposed to play a keyrole in the regulation of isoprenoid biosynthesis. Here we report the isolation and functional characterization of a 1959- bp Dunaliella salina HDR (DsHDR) cDNA encoding a deduced polypeptide of 474 amino acid residues. Phylogenetic analysis implied a cyanobacterial origin for plant and algal HDR genes. Steady-state DsHDR transcript levels were higher in D. salina cells submitted to nutritional depletion, high salt and/or high light, suggesting that DsHDR may respond to the same environmental cues as genes involved in carotenoid biosynthesis.
    2009Journal article Restricted access Show more