ULTRASTRUCTURAL AND BIOCHEMICAL-CHANGES IN POTATO-TUBER CELLS RELATEDTO TUMORIGENESIS

Tumours were induced on potato (Solanum tuberosum L.) tuber discs with Agrobacterium tumefaciens, B6S3. Control and tumour cells were compar ed in their ultrastructures. Chloro-amyloplasts were characteristic fo r the control cells, while in tumour cells leukoplasts or even proplas tids were found. The tumour cells were smaller, rich in cytoplasm and their nuclei were irregular in shape. Soluble protein patterns of cont rol and tumour tissues differed in polypeptide, representing a large s ubunit of ribulose-1,5-bisphosphate carboxylase (RuBisCO) and storage protein patatin, present only in the control extracts. The only tumour -related polypeptide was that of about 39 kDa. For isolated plastides, differences were found in membrane protein fractions. Control membran es contained greater quantities of light-harvesting complex II (LHCII) polypeptides, while tumour membranes were characterized by greater am ounts of tight-harvesting complex I (LHCI) polypeptides, which was in accordance with electron microscopy results.