Biopolymers and cell. 2000; 16 (3): 159 - 185

Genome variability in the somatic plant cells. 6. Variability and selection in the course of adaptation to in vitro conditions

V. A. Kunakh

Data on the dynamics of the cell population genetic structure as well as the role and peculiarities of the selection effects in the course of the cell adaptation to in vitro conditions have been reviewed. Effect of the growth conditions, role of the genotype, phytohormones and other factors that control the variability and selection trends liave been discussed. The plant cell adaptation has been shown to be the multistage event. The physiological adaptation to the conditions of maintenance in vitro is observed on the early steps of the culturing, later on there occur the processes of the genetic adaptation manifested as a change in tlie cell population genetic structure. In the course of adaptation the representative strain samples exhibit ail types of the population genetic structure evolution i. e. divergence, convergence and parallelism. Three periods in the adaptation process have been revealed: (i) the primary population of isolated cells, (ii) the strain formation and (Hi) the established strain. These periods are determined by the type, mainstream, and rigidity of the selection operating in the cell population. The established (adapted) strains are characterized by the physiological and genetic homeo-stasis that preferentially results from the action of stabilizing selection. It has been concluded that celt adaptation to the conditions of long-term maintenance in the passaged culture is the process of formation of the novel biological system as a result of the effect of the major driving factors of evolution, viz., variability, heredity, selection and possibly gene (genotypes) drift. On the whole, the phenomenon studied may provide a model of the profound (but reversible) regressive evolution of the biological system — from the multicellular level to the unicellular one.