Loss of plant organogenic totipotency in the course of in vitro neoplasticprogression

The aptitude for organogenesis from normal hormone-dependent cultures very commonly decreases as the tissues are serially subcultured. The reasons for the loss of regenerative ability may vary under different circumstances: g enetic variation in the cell population, epigenetic changes, disappearance of an organogenesis-promoting substance, etc. The same reasons may be evoke d for the progressive and eventually irreversible loss of organogenic totip otency in the course of neoplastic progressions from hormone-independent tu mors and hyperhydric teratomas to cancers. As in animal cells, plant cells at the end of a neoplastic progression have probably undergone several inde pendent genetic accidents with cumulative effects. They indeed are characte rized by atypical biochemical cycles from which they are apparently unable to escape. The metabolic changes are probably not the primary defects that cause cancer, rather they may allow the cells to survive. How these changes , namely an oxidative stress, affect organogenesis is not known. The litera ture focuses on somatic mutations and epigenetic changes that cause aberran t regulation of cell cycle genes and their machinery.