Abstract:

Endophytic fungus of Phomopsis isolated from birch(Betula platyphylla) bark can be used as an elicitor to induce accumulation of triterpenoids in birch cell suspension culture. The change of dry weight and triterpenoids content of birch suspension cell were investigated at early growth phase, exponential growth phase and late growth phase after a fungal elicitor of 40, 100, and 400 μg ·mL^-1 concentration was added to birch suspension cells. Results showed that different induction schemes all promoted accumulation of triterpenoids, while the treatments reduced the dry weight of birch cells. Suspension cells at exponential growth phase were most easy to be induced, and 40 μg ·mL^-1 fungal elicitor enhanced the triterpenoids content to 29.47 mg ·g^-1, increasing by 78% than that of the control. We investigated changes in pH and conductivity of the medium, and the activity of phenylalanine ammonialyase (PAL) and peroxidase (POD) under the optimal induction condition. Results showed that the fungal elicitor induced alkalinization of the medium and increased the conductivity, and significantly increased the activity of PAL and POD of birch suspension cells, which was 5.70 and 5.74 fold as high as the control after 6-10 h of treatment, respectively. These results suggested that fungal elicitation induced defense reaction in birch suspension cell. General phenylpropanoid pathway and oxidative burst might involved in the triterpenoids accumulation induced by the fungal elicitor.

Key words: Betula platyphylla, fungal elicitor, triterpenoids, suspension culture