Total DNA 5-methylcytosine level of rice calli derived from protoplasts is independent of regeneration ability

To study the roles of m5C in the differentiation of rice calli derived from protoplasts (protoclones), the m5C level of the total DNA was analyzed using the32P post-labeling method. The level of m5C in regenerable and nonregenerable protoclones was similar, as was in calli and leaves of plants regenerated from the same protoclones. Treatment with 0.5 mM 5-azacytidine caused significant reduction of the level of m5C and of the regeneration frequency of callus. Significantly increased m5C levels were observed during prolonged culture.