MASSIVE ACCUMULATION OF PHYTOENE INDUCED BY NORFLURAZON IN DUNALIELLA BARDAWIL (CHLOROPHYCEAE) PREVENTS RECOVERY FROM PHOTOINHIBITION1 |
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Authors: | Ami Ben-Amotz Jonathan Gressel Mordhay Avron |
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Institution: | 1. Department of Plant Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;2. Department of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel |
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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 phytoene 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 β-carotene and in the norflurazon-treated phytoene-rich cells. These observations are in agreement with the hypothesis that the accumulated β-carotene in Dunaliella bardawil protects the cells against injury by excessive irradiation. |
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Keywords: | β-carotene Dunaliella photoinhibition phytoene |
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