Calcium-Calmodulin complex mediates the trans-differentiation of Zinnia elegans leaf mesophyl! cells in to tracheary elements in cell suspension culture

Abstract

Leaf mesophyll cells of Zinnia elegans cv Envy could be induced to be frans differentiated in to tracheary elements by anxin and cytokmin in cell suspension culture) with peak differentiation at 96 hours, which has been used as a model system in studying the physiology and biochemistry of cellular differentiation. In the present study, the involvement of calcium ions and calmodulin (CaM) in the process of tracheary element (TE) differentiation was examined. Calcium chelator EGTA was used to deplete the Ca2+ concentration in the medium while calmodulin inhibitors triffluoferazsn (TFP) and chlorpromazine (CPZ) were used to inhibit the calmodulin activity. Blocking the Ca2+ sequestration with 0.1 mM EGTA and the inhibition of calmodulin action by TFP and CPZ at 10 and 20 pM concentrations significantly inhibited the TE differentiation process. It implies that, Ca2+ itself and Ca/CaM complex has a specific role to play in the trans-differentiation process of Zinnia mesophyl! cells in to tracheary elements. Further increase in EGTA upto O.SmM, TFP and CPZ upto 40 juM concentrations resulted a high rate of ceil death probably due to non-specific toxic effects, which may lead to membrane damage.