ADENYLATE KINASE IN TOBACCO CELL-CULTURES .2. VARIABILITY AND REGULATION OF ISOFORM ACTIVITY PATTERNS IN DIFFERENT CELL-LINES

Specific activity and isoform patterns of adenylate kinase (AK) were i nvestigated in tissue cultures of cloned tobacco cell lines that diffe red mainly in hormone requirement, proximate cause of hormone-autotrop hy and neoplastic growth characteristics. Variations in the AK isoform pattern were related to growth and ageing processes, differentiation state of tissues, differences between culture cycles as well as the ne oplastic characteristics of the cell lines. High specific AK activity and isoform patterns with dominating chloroplastic activities appeared as typical of green, photosynthetic and actively growing tissues (cal li in growth phase, callus outer tissues). Lower specific AK activity and isoform patterns with dominating cytosolic activity were typical f or senescent or non-photosynthetic tissue (calli in stationary phase, callus core tissues), but sometimes also occurred in entire young call i, apparently as a consequence of stress. This isoform pattern is ther efore proposed as a stress marker in plant cell cultures. The isoform patterns of the different cell lines were analyzed in detail for the V ariations during different culture cycles and the differences appearin g under optimal growth conditions. The observed characteristics were r elated to proximate cause of hormone-autotrophy and neoplastic state. The main differences appeared between normal and neoplastic, transform ed tissues. Changes in compartmentation of AK activities under differe nt metabolic situations are discussed with respect to the physiologica l characteristics of the cell lines, energy metabolism and ATP/ADP rat ios of cellular compartments and the presumed role of AK in ageing and stress.