Peptide mapping of the ribulose bisphosphate carboxylase small subunit from the somatic hybrid of tomato and potato

Abstract

Five somatic hybrids of potato and tomato obtained by protoplast fusion were identified using the isoelectric focusing patterns of ribulose bisphosphate carboxylase as phenotypic markers of the nuclear and chloroplast genomes. Together with the previously analyzed hybrids (14) this brings the number of verified somatic hybrids between the two species to nine. The products of both tomato and potato nuclear genomes are present in the ribulose bisphosphate carboxylase oligomer from all nine hybrids. Four of the hybrids contain the tomato large subunit and hence the tomato chloroplast DNA is functional, whereas in five hybrids the potato ribulose bisphosphate carboxylase large subunit and thereby the potato chloroplast DNA is present. The former are designated topatoes and the latter pomatoes (11).Mapping of chymotryptic peptides of the small subunit of tomato and potato revealed a tyrosine containing peptide with species specific mobility. Peptide maps from an analyzed somatic hybrid contained both the tyrosine peptide specific for potato and that specific for tomato. Maps of tryptic peptides of the small subunit of tomato differed from those of the potato in 2 peptides. The tryptic peptide maps of one analyzed hybrid contained the two peptides unique to potato as well as the two peptides unique to tomato. The tomato-potato hybrids are aneuploid with chromosome numbers ranging from 48 to 74, the expected allotetraploid number being 48 and the expected allohexaploid number 72.