UV-A SPECIFIC REGULATION OF ANTHOCYANIN BIOSYNTHESIS IN RED TURNIP, BRASSICA RAPA L. SUBSP. RAPA: UV-A MEDIATED PROTEIN PHOSPHORYLATION

The swollen hypocotyls of the ‘Tsuda’ cultivar of red turnip exhibited sunlight dependent anthocyanin accumulation and chalcone synthase gene (CHS) expression. However, these same cellular responses were not observed in the cv. Yurugi-Akamaru. CHS expression was enhanced by repeating daily 6-hour exposures to sunlight in ‘Tsuda’. Anthocyanin production was also induced by a 6-hour UV-A irradiation trial, after subsequent incubation in darkness for more than 15 h. The minimum length of UV-A exposure required was less than two hours. Phosphoprotein detection by western blotting showed that a 51-kDa protein was phosphorylated after 5 min. of UV-A exposure and its dephosphorylation was complete within 120 min. of the exposure.