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MASSIVE ACCUMULATION OF PHYTOENE INDUCED BY NORFLURAZON IN DUNALIELLA BARDAWIL (CHLOROPHYCEAE) PREVENTS RECOVERY FROM PHOTOINHIBITION1
Authors:Ami Ben-Amotz  Jonathan Gressel  Mordhay Avron
Institution:1. Israel Oceanographic & Limnological Research, Tel-Shikmona, P.O.B. 8030, Haifa 31080, Israel

Address for reprint requests and correspondence.;2. Department of Plant Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;3. Department of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel

Abstract:The effects of nanomolar to micromolar concentrations of the herbicide norflurazon were studied in Dunaliella bardawil Ben-Amotz et Avron, a β-carotene-accumulating halotolerant alga. The large amount of β-carotene which Dunaliella bardawil can contain, around 8% of the algal dry weight, is reduced to 0.2% by treatment with 100 nm norflurazon. Simultaneously, phytoene is accumulated to a similar level of about 8%. The gradual increase in phqtoene content, in response to increasing norflurazon concentrations, corresponds to the decrease in β-carotene, with no evident change in other isoprenoid intermediates. Carotene-rich Dunaliella bardawil is substantially resistant to high-intensity photoinhibition. This resistance is lost in cells grown to contain low & carotene and in the nor-urazon-treated phytoene-rich cells. These obseruations are in agreement with the hypothesis that the accumulated β-carotene in Dunaliella bardawil portects the cells against injury by excessive irradiation.
Keywords:β-carotene  Dunaliella  photoinhibition  phytoene
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