Phosphorylation of a protein (pp56) is related to the regeneration of rice cultured suspension cells.

Short-term cultured suspension cells of rice (Oryza sativa L.) are capable of regeneration, but not in long-term culture. For clarification of the mechanism of regeneration, protein phosphorylation in short-term and long-term cultured suspension cells was compared by two dimensional-polyacrylamide gel electrophoresis. A 56 kDa protein having an isoelectric point of 4.5 was phosphorylated in vitro in short-term cultured suspension cells, but was not phosphorylated after regeneration. This protein in long-term cultured suspension cells remained phosphorylated after transfer to the regeneration medium. However, using an antibody raised against this protein from short-term cultured suspension cells, it was always detected in long-term and short-term cultured suspension cells after transfer to the regeneration medium. The partial amino acid sequence of the HPLC-purified protein showed homology to a calcium-binding protein from maize. The phosphorylation of the 56 kDa protein (pp56) appears to be associated with the regeneration of cultured rice cells.