Somatic embryogenesis: from discovery through investigation to application

Plant cells possess the remarkable ability to adapt to environmental changes. It is manifested by formation of embryos directly from the cells of plant body, bypassing the fertilization stage. These embryo structures develop into complete plants. The process itself, to distinguish the path of formation and emphasize consistency with zygotic embryogenesis, is referred to as somatic embryogenesis (SE). Although more than 60 years have passed since the first publication on the phenomenon has been written, the mechanism of reprogramming of a somatic cell into an embryogenic one is still not fully understood. This is a critical step in SE that can be induced by exo- and endogenous factors and stress treatments. The exposition of plant material to these factors affects the reorganization of the chromatin structure and gene expression, which can consequently trigger the program of embryogenesis. The paper reviews current knowledge on how the identity of totipotent cells is determined and the which stimuli are required to reprogram somatic cell development. Knowledge of key molecular regulators and the network of relationships that control the SE induction is summarized. Issues that are important for enhancing the understanding of the mechanisms underlying totipotency are also defined. Finally, the practical potential of SE is demonstrated, and examples of its use are provided.