BEAN (PHASEOLUS-VULGARIS L) PROTOPLASTS AS A MODEL SYSTEM TO STUDY THE EXPRESSION AND STABILITY OF RECOMBINANT SEED PROTEINS

A suitable protocol for the transient expression of seed protein genes in protoplasts derived from cell suspension cultures of common bean h as been established. Preliminary analyses of cultures to verify the sy nthesis of phaseolin - actively accumulated by the starting tissue, th e developing cotyledon - showed that the protein was no longer synthes ised after 5 days of culture. Transient expression of a phaseolin sequ ence, driven by a constitutive promoter, resulted in the accumulation of the correctly glycosylated and assembled protein. This system, when compared to tobacco protoplasts, largely avoids phaseolin fragmentati on and the presence of contaminant polypeptides in the immunoprecipita tes. Therefore, bean protoplasts are a good system to study the expres sion of wild-type as well as in-vitro-modified bean seed proteins.