Regulation of Anthocyanin Synthesis in Apple Skin. III. Involvement of Phenylalanine Ammonia-lyase

Abstract

The relationship between L-phenylalanine ammonia-lyase (PAL) activity and anthocyanin synthesis in apple skin was investigated. Enzyme activity was induced by exposure to white light. After a lag phase of less than 10 h, PAL activity increased to a maximum at 30 h and then declined. Anthocyanin accumuIation, after a lag phase of 20 h, continued at a constant rate for a further 100 h. The increased rate of anthocyanin accumulation which resulted from u.v. light and cycloheximide treatment of whole fruit was preceded by comparable increases in the level of PAL activity. Wounding, which stimulated anthocyanin synthesis in skin discs, caused a far greater increase in PAL activity. In wounded tissue (skin discs) neither u.v. light or cycloheximide treatment caused any increase in anthocyanin accumulation or PAL activity. Cycloheximide inhibited anthocyanin formation in skin discs and, to a lesser extent, reduced PAL activity. When cycloheximide was applied as a single drop to a whole fruit, it inhibited anthocyanin formation but increased PAL activity in the skin to which it was applied. In a surrounding ring of skin, both anthocyanin level and PAL activity were increased. Without light, anthocyanin synthesis did not occur and there was virtually no PAL activity in whole fruit skin. However, in skin discs held in the dark, PAL activity developed to the same level as in illuminated discs, but no anthocyanin accumulated. The results indicate that, although the level of PAL activity may control the rate of anthocyanin synthesis in whole fruit, it is not the only critical enzyme regulating anthocyanin synthesis in apple skin. The mechanisms by which treatments may stimulate PAL activity and anthocyanin synthesis and the possible involvement of ethylene are discussed.

Changes in L-Phenylalanine Ammonia-lyase Activity and Anthocyanin Synthesis during Berry Ripening of Three Grape Cultivars

“…`Super Hamburg' accumulated more anthocyanin and phenols in the skin and higher PAL activity than `Kyoho' in this period. Such a close relationship between PAL activity and anthocyanin accumulation has been observed with other fruit species; e. g. strawberries (7), peaches(1) and apples (6,19).…”

“…PAL extraction and assay : PAL was extracted by the method based on that of Faragher and Chalmers (6).…”

Changes in phenolics and antioxidant property of peach fruit during ripening and responses to 1-methylcyclopropene

“…Compared with the control peach, the application of 1-MCP treatment had insignificant effect (p > 0.05) on the protocatechuic acid. (Faragher and Chalmers, 1977)) showed a relationship between ethylene production, anthocyanidin accumulation and phenylalanine lyase activity in apple fruit. Therefore, it was reasonable to suggest that inhibition of ethylene production by 1-MCP may lead to reduced concentration or interruption of normal metabolism of phenolic compounds in 1-MCP treated fruit.…”

Anthocyanin, antioxidant activity and stress-induced gene expression in high CO2-treated table grapes stored at low temperature

“…PAL was extracted from 5 g of skin according to the method of Faragher and Chalmers (1977). The skin was ground in 25 ml of 100 mM H 3 BO 3 -NaOH buffer (pH 8.8) containing 25 mM 2-mercaptoethanol and 6% PVP.…”