Possible regulatory role of phenylalanine ammonia-lyase in the production of anthocyanins in asparagus (Asparagus officinalis L)

The regulatory role of phenylalanine ammonia-lyase (PAL) in the light-induced accumulation of anthocyanins in the epidermis of asparagus spears has been analysed. A correlation between the stimulation of PAL activity and the rise in total anthocyanin content has been observed. Light radiation induced PAL activity, which in turn stimulated anthocyanin accumulation, a hypothesis which has been confirmed by treating asparagus spears with S-carvone, an inhibitor of PAL activity. A marked delay was observed in the rise in PAL activity and total anthocyanin content in asparagus spears treated with this compound during light irradiation. PAL activity and anthocyanin synthesis continued when the spears were stored in darkness for 5 days after being subjected to light, but the inhibitory effect of S-carvone remained during this storage. When the asparagus spears were immersed in water for 20 h, no PAL activity could be detected and scarcely any total anthocyanin content was measured. However, after 5 days of storage in darkness a sharp upsurge in PAL activity was found, which was not translated into a parallel increase in total anthocyanin content. (c) 2005 Society of Chemical Industry.