The effects of salicylic acid and glucose on biochemical traits and taxane production in a Taxus baccata callus culture

The combined use of elicitors can be an effective way to increase the production of secondary metabolites (SMs) in plant cell, tissue and organ cultures. This study investigated the effects of a salicylic acid (SA) pretreatment and different glucose levels on the growth, biochemical traits and taxane production in a Taxus baccata callus culture. For this purpose, after a pretreatment with SA (5 mu M), three-month-old calli were cultured on B5 medium fortified with different concentrations of glucose (0, 0.5, 1, 2 and 3%), and they were compared with calli cultured on a B5 medium supplemented only with glucose. When the calli were harvested at 21 days, their fresh weight (g), dry weight (g) and cell viability (%) had decreased significantly (p < 0.05) with the higher glucose concentrations. The glucose treatment increased the hydrogen peroxide (H2O2) and malondialdehyde (MDA) content, and caused oxidative stress in treated tissues. The lower H2O2 content and oxidative stress was associated with an increased antioxidant enzyme activity in the SA-pretreated samples, which resulted in less membrane damage and improved growth and cell viability under the glucose treatment compared to the control. By reducing the activity of phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO), the SA pre-treatment reduced the production and oxidation of phenolic compounds under the glucose treatment; this decrease was associated with less browning of tissues and higher viability. Increases in taxol (5.1-fold) and total taxanes (3.5-fold) in the SA-pretreated calli cultured on the medium containing 2% glucose, compared to the control, indicated that the two treatments had a significant effect on taxane production in the T. baccata callus culture.