Synergistic effects of light and temperature on anthocyanin biosynthesis in callus cultures of red-fleshed apple (Malus sieversii f. niedzwetzkyana)

We established a red callus from the leaves of a red-fleshed apple individual, which was a hybrid offspring of the cross between Malus sieversii f. niedzwetzkyana and Malus domestica cv. 'Fuji'. We analyzed callus growth and anthocyanin biosynthesis/metabolism under different combinations of temperature and light conditions. Incubation in darkness resulted in decreased anthocyanin accumulation, while it promoted callus growth. Exposure to light and low temperature (16 A degrees C) induced the expression of MYB10 and bHLH3/33, which are responsible for coordinating the regulation of anthocyanin biosynthesis, as well as the expression of other structural genes. Treatments with light and high temperature (32 A degrees C) induced MYB16 expression, which repressed anthocyanin biosynthesis. Additionally, low temperature (16 A degrees C) inhibited the expression of MYB111. We analyzed the expression patterns of MYB and bHLH transcription factor genes by quantitative real-time polymerase chain reaction. Our data suggest that light-induced regulation of anthocyanin biosynthesis is primarily caused by altered MYB10 transcript levels, while temperature-induced regulation is the result of changes to the expression of bHLH3/33, MYB16, MYB17, MYB111, and other repressors. In conclusion, we investigated the reciprocal effects of light and temperature on anthocyanin biosynthesis in red-fleshed apple calli. Our findings may provide a theoretical basis for breeding red-fleshed apple varieties with high anthocyanin contents.