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Effects of Glucose on the Growth of Phaeodactylum tricornutum, Fucoxanthin Content and Related Gene Expression

??OBJECTIVE To explore the effects of glucose on the growth of algae, the content of fucoxanthin, and expressions of genes related to biosynthesis of fucoxanthin. METHODS The cell growth of algae induced by glucose was researched by using spectrophotometric method. The content of fucoxanthin was measured by HPLC. The expressions of the genes which were related to biosynthesis of fucoxanthin were detected by using quantitative PCR. RESULTS At the end of the platform period, the density of cells treated by glucose was higher than that of the control group. The growth of P. tricornutum was promoted by glucose. The result of HPLC analysis showed that fucoxanthin content in the algae treated by different concentrations of glucose was decreased than that in the control group. When the concentration of glucose reached 50 mg??L^-1, the content of fucoxanthin was the lowest (0.26 mg??g^-1 DW), which was 67.5% lower than the control, indicating that glucose inhibited the biosynthesis of fucoxanthin in P. tricornutum. RT-qPCR result showed that the expression of genes related to the biosynthesis pathway of fucoxanthin, i.e., zep, pys, zds, lcyb, crtiso, and pds, were all lower than those of the control when the concentration of glucose was in the range from 10 to 50 mg??L^-1. This result was consistent with the change of fucoxanthin content. CONCLUSION This result further illustrates that glucose may inhibit the biosynthesis of fucoxanthin in P. tricornutum by down-regulating the expression of related genes.