THE EMBRYOGENESIS OF PLANT SOMATIC CELLS

Abstract

Embryogenesis in plants is not restricted to the fertilized egg cell but can be naturally or artificially induced in many different cell types, including somatic cells. Although genetic components clearly determine the potential of species/genotypes to form somatic embryos, the expression of embryogenic competence at the cellular level is defined by developmental and physiological cues. Competent cells can respond to a variety of conditions by the initiation of embryogenic development. In general, these conditions include alterations in auxin (exogenous and/or endogenous) levels and evoke stress responses. Recent experimental results in the field of developmental and molecular plant biology emphasize the role of chromatin remodelling in the coordination of overall gene expression patterns associated with developmental switches. It can be hypothesized that the initiation of somatic embryogenesis is a general response to a multitude of parallel signals (including auxin and stress factors). In addition to cellular and physiological reorganization, this response includes the extended remodelling of the chromatin and a release of the embryogenic programme otherwise blocked in vegetative cells by chromatin-mediated gene si1encing. In this paper we attempt to give a general overview of experimental results supporting the aforementioned hypothesis. In addition, we also outline our results at The Dalat Affiliate Institute of Biology (Vietnam) on somatic embryogenesis of Potato, Lilium spp., Carnation,  halaenopsis spp., Lisianthus spp., Paulownia spp., Orr-a sativa L., Rose, Strawberry, Cymbidium spp., Gloxinia, Panax vietnamensis, Tea, Anthurium spp., and some native Orchids.