Evolution of cell populations in vitro: Peculiarities, driving forces, mechanisms and consequences

Abstract

This review outlines the major features and distinctions of cell populations, types and directions of selection in such populations. Population-genetic basis for cell adaptation to growth conditions in vitro is elucidated; in particular, peculiarities ofgenome evolution in the course ofcell dedifferentiation and further cell adaptation to growth conditions in passaged culture are evaluated. Main factors ofvariation and selection in cell populations in vitro, influence ofgrowth conditions on structure ofcell populations and some regularities ofcultured cells and regenerated plants are considered. Details of creation of stable cell lines-producers of biologically active substances are presented. Views and suppositions ofauthor resulting from analysis ofboth literature data and own multiyear studies on cell population genetics are set forth. Among others are substantiated such key statements: cell culture in vitro presents dynamically-heterogeneous biological system, clone population, which is developing (evolving) as a result of major driving factors of evolution - variation, heredity, selection and drift of genes (genotypes); interaction between these processes determines the biological characteristics of each particular cell line grown in specific conditions; in adaptation ofcells to growth conditions in vitro one can single out three periods: the initial population of isolated cells, the period of strain (cell line) formation and the established strain. The division into periods is determined by the type, direction and intensity of «natural» selection that acts in cell population. The formed (adapted to growth in vitro) strains are genetically heterogeneous, they are characterized by the presence ofphysiological and genetic homeostasis, which are mostly caused by the action ofstabilizing selection; cultured cells of higher plants are able to synthesize practically all classes ofsecondary (specialized) compounds (alkaloids, steroids, terpenoids, etc.); any somatic cell with living (functionally active) nucleus during its isolation and further cultivation in tissue culture, as a result ofthe process of«somaclonal» variabilityoccur-ring according to the N. I. Vavilov's law of homologous series in hereditary variability, can restore in it's descendants, including regenerated plants, the entire genetic polymorphism (or at least a significant part ofit) characteristic of the plant's species and may be even it's genus. This provides an opportunity to preserve and restore the natural polymorphism in cultured cells and tissues in vitro.