Induced beta-carotene synthesis driven by triacylglycerol deposition in the unicellular alga Dunaliella bardawil

• Published in: Plant physiology (Bethesda) Vol. 116; no. 4; pp. 1239 - 1248
• Main Authors: Rabbani, S. (Universitat Freiburg, Freiburg, Germany.), Beyer, P, Lintig, J.V, Hugueney, P, Kleinig, H
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-04-1998
• Subjects: ACETYL-COA CARBOXYLASE; Algae; beta -carotene; BIOCHEMICAL PATHWAYS; Biochemistry and Enzymology; Biological and medical sciences; BIOSYNTHESIS; CAROTENOIDS; CELL STRUCTURE; Chromoplasts; DUNALIELLA; Dunaliella bardawil; Enzymes; ENZYMIC ACTIVITY; Fatty acids; Fundamental and applied biological sciences. Psychology; LIGASES; LIGHT; LIGHT INTENSITY; Lipids; LOCALIZATION; Messenger RNA; Metabolism; NUTRIENT DEFICIENCIES; PHYTOENE; Plant physiology and development; Plants; PLASTIDS; Storage and secretion, pigments, phytochrome; STRESS RESPONSE; TRANSCRIPTION; TRANSLATION; triacylglycerol; TRIGLYCERIDES; ULTRASTRUCTURE; Algae; Chlorophycophyta; Environmental factor; Biosynthesis; Stress; Regulation(control); Dunaliella; Triacylglycerol; Light; Sequestering power; Betacarotene; Biological accumulation; Deposition; Thallophyta
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.116.4.1239

Under stress conditions such as high light intensity or nutrient starvation, cells of the unicellular alga Dunaliella bardawil overproduce beta-carotene, which is accumulated in the plastids in newly formed triacylglycerol droplets. We report here that the formation of these sequestering structures and beta-carotene are interdependent. When the synthesis of triacylglycerol is blocked, the overproduction of beta-carotene is also inhibited. During overproduction of beta-carotene no up-regulation of phytoene synthase or phytoene desaturase is observed on the transcriptional or translational level, whereas at the same time acetyl-CoA carboxylase, the key regulatory enzyme of acyl lipid biosynthesis, is increased, at least in its enzymatic activity. We conclude that under normal conditions the carotenogenic pathway is not maximally active and may be appreciably stimulated in the presence of sequestering structures, creating a plastid-localized sink for the end product of the carotenoid biosynthetic pathway