Hybrid cell lines Arabidopsis thaliana + Brassica campestris: No evidence for specific chromosome elimination

Protoplasts from callus tissue of Arabidopsis thaliana and from leaves of Brassica campestris were fused using the PEG-high pH-high Ca++-technique. Single dividing fusion products were isolated mechanically and cultured further in 1 μl microdroplets. 31 cell lines each originating from a single fusion event have been obtained. Cytological analysis of 6 cell lines was conducted 4–7 months after isolation. All metaphases examined contained chromosomes of both species. Both Arabidopsis and Brassica specific chromosomes were still retained in cells of 7 month old cultures. Reconstituted di- and multiconstrictional chromosomes were also observed. Biochemical analysis of 12 cell lines was performed in 6–7-month old cultures. Electrophoresis on PAG and specific staining for esterase, lactate dehydrogenase, and peroxidase activities revealed isozymes of both parents to be present in all cell lines. The data obtained are interpreted as evidence for retention and functional activity in hybrid cells of specific chromosomes from each species for at least 7 months of culture.