This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (76) Citing Articles via Google Scholar Google Scholar Articles by Ben-Amotz, A. Articles by Avron, M. Search for Related Content PubMed PubMed Citation Articles by Ben-Amotz, A. Articles by Avron, M. Agricola Articles by Ben-Amotz, A. Articles by Avron, M.

Metabolism and Enzymology

Stereoisomers of -Carotene and Phytoene in the Alga Dunaliella bardawil

National Institute of Oceanography, Israel Oceanographic & Limnological Research, Tel-Shikmona, P. O. B. 8030, Haifa 31080, Israel, Department of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel

Dunaliella bardawil, a halotolerant green alga, was previously shown to accumulate high concentrations of -carotene when grown outdoors under defined conditions. The -carotene of algae cultivated under high light intensity in media containing a high salt concentration is composed of approximately 50% all-trans -carotene and 40% 9-cis -carotene. We show here that the 9-cis to all-trans ratio is proportional to the integral light intensity to which the algae are exposed during a division cycle. In cells grown under a continuous white light of 2000 microeinsteins per square meter per second, the ratio reached a value of around 1.5, while in cells grown under a light intensity of 50 microeinsteins per square meter per second, the ratio was around 0.2. As previously shown, algae treated with the herbicide norflurazon accumulate phytoene in place of -carotene. Electron micrographs showed that the phytoene is accumulated in many distinct globules located in the interthylakoid spaces of the chloroplast. Here too, two isomers are present, apparently all-trans and 9-cis phytoene, and their ratio is dependent upon the integral light intensity to which the algae are exposed during a division cycle. In the presence of norflurazon, Dunaliella bardawil grown under a light intensity of 2000 microeinsteins per square meter per second contained about 8% phytoene with a 9-cis to all-trans ratio of about 1.0. This ratio decreased to about 0.1 when the light intensity was reduced to 50 microeinsteins per square meter per second. These data suggest that the isomerization reaction which leads to the production of the 9-cis isomer occurs early in the path of carotene biosynthesis, at or before the formation of all-trans phytoene. The presence of the 9-cis isomer of -carotene and the dependence of its preponderance on light intensity seem to be a common feature of many plant parts. Thus carrots which are exposed to minimal light contain no 9-cis isomer while sun-exposed leaves, fruits, and flowers contain 20 to 50% of the 9-cis isomer.

This article has been cited by other articles:

				A. Harari, D. Harats, D. Marko, H. Cohen, I. Barshack, Y. Kamari, A. Gonen, Y. Gerber, A. Ben-Amotz, and A. Shaish A 9-cis {beta}-Carotene-Enriched Diet Inhibits Atherogenesis and Fatty Liver Formation in LDL Receptor Knockout Mice J. Nutr., October 1, 2008; 138(10): 1923 - 1930. [Abstract] [Full Text] [PDF]

				A. Bonora, S. Pancaldi, R. Gualandri, and M. P. Fasulo Carotenoid and ultrastructure variations in plastids of Arum italicum Miller fruit during maturation and ripening J. Exp. Bot., May 1, 2000; 51(346): 873 - 884. [Abstract] [Full Text] [PDF]

				S. C. Orset and A. J. Young Exposure to Low Irradiances Favors the Synthesis of 9-cis beta ,beta -Carotene in Dunaliella salina (Teod.) Plant Physiology, February 1, 2000; 122(2): 609 - 618. [Abstract] [Full Text]