Effect of salicylic acid on DNA methylation in Thymus daenensis Celak. under hyperhydricity syndrome

Thymus daenensis Celak. is an endemic plant in Iran and In vitro culture is useful for its propagation. Hyperhydricity syndrome is a common problem in In vitro culture causing abnormalities in growth and development of in vitro plants. In this investigation we studied the effect of benzyladenine and salicylic acid on DNA methylation of hyperhydric shoots. For this purpose, seeds were cultured into glass jar having benzyladenine and salicylic acid. Active oxygen and antioxidant enzymes analyses were done. Proline and H2O2 levels were high in BA treated-plantlets and also in plantlets growing without hormone but SA that reversed hyperhydric shoots to normal status, reduced the content of prolin, H2O2 and antioxidant enzymes. No statistical differences were observed in organelles DNA methylation, but 5 µM SA decreased the nuclear DNA methylation. Defense activator SA may have triggered genes engaged in stress response with an increase of proteins. Probably the decrease of methylation under SA treatment may be related with the reversion of hyperhydricity.