Euploidy in Ricinus. I. Euploidy and gene dosage effects on cellular proteins.

Investigations of an euploid series of castor bean, Ricinus communis L., Consisting of haploid, diploid, and tetraploid individuals, was performed to determine the value of such a series in studying the biochemical consequences of genome multiplication. The effects of euploidization of the nuclear genome on the biosynthesis of cellular proteins were examined. Extracts of total soluble proteins from 10-day-old leaves of all three ploidy levels examined by electrophoresis on polyacrylamide gels revealed no difference in the complement of proteins present; however, differences in intensity of several protein bands were detected. Analysis of esterases isozyme activity by isoelectric focusing revealed both increases and decreases in the activity levels of individual isozyme variants in responses to changes in ploidy levels. Results from this analysis are discussed in terms of possible regulatory mechanisms active in the regulation of duplicated genes.