Abstract
Similar to many plants, the leaves of Begonia semperflorens accumulate anthocyanins and turn red in autumn. This induction of anthocyanin biosynthesis in autumn has been attributed to low temperature, but the effects of light on this process are still under debate. In the present work, light was found to be necessary for anthocyanin biosynthesis under low temperature. When seedlings were exposed to light and low temperature, both upstream (phenylalanine ammonialyase and chalcone isomerase) and downstream [dihydroflavonol 4-reductase (DFR), flavonoid-3-O-glucosyltransferase (UFGT)] enzymes of the anthocyanin biosynthesis pathway were activated. However, when seedlings were exposed to low temperature in the dark, downstream enzymes (DFR and UFGT) were inhibited. The carbon flux caused by blocked anthocyanin biosynthesis in the dark-exposed plants channeled into flavonoid (for example, flavonol) and phenolic acid, but not lignin, biosynthesis.
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