Laboratory of Radiation Genetics and Chemical Mutagenesis, Faculty of Agriculture, University of Tokyo, Bunkyo-ku, Tokyo, 113 Japan
Auxins and cytokinins, two types of phytohormones, plant an important role in
the callus initiation and regeneration. We have focussed attention on the
experimentally-induced reorganization of rice callus. Water- and alcohol-
soluble proteins were extracted from both induced callus on the auxin (2, 4-D)-
containing medium and regenerating callus on the cytokinin (6-
benzylaminopurine)-containing medium.
For the water-soluble fraction, 30 bands were detected after the S.D.S. -polyacrylamide gel electrophoresis (Fig. 1). One band detected at the 17,000 dalton position was always present and increased amounts day by day in the regenerating callus. After the electrophoresis of the alcohol-soluble fraction, 12 bands were detected (Fig. 1). The major band detected at the 38,000 dalton position was present in the induced calli, but practically disappeared by 5 days after subculture on the regeneration medium containing cytokinins. Another band at the 46,000 dalton position appeared in the regenerating calli, while it was absent in the induced calluses. All bands obtained from calli subcultured on the regeneration medium were maintained with no significant changes for about one month.
Thus, we have found a promising tissue culture system for studying hormonal action at the molecular level in rice. We plant to find out whether the production of the proteins in regenerating calli is transcriptionally regulated or not.
Fig. 1. SDS polyacrylamide gel band pattern.