Cell cultures totipotency

Another aspect of LIF was revealed by studies on the activity that prevents differentiation of totipotent ES cells derived from normal blastocysts (Williams et al., 1988 Smith et al., 1988 Gough et al., 1989 Smith et al., 1992). It is known that to maintain the totipotency of ES cells, they must be grown on a feeder layer of fibroblasts. The activity secreted by the feeder layer fibroblasts, termed DIA (differentiation inhibitory activity) or DRF (differentiation retarding factor), has been purified, and its characteristics suggest that DIA/DRF may be identical to LIF. Indeed, not only does LIF exhibit the same activities as DIA and DRF in vitro, but also ES cells cultured with LIF can retain their totipotency. When the ES cells treated with LIF are injected into mouse blastocysts and then introduced into pseudo-pregnant females, they contribute extensively to the development of all of the somatic tissues (Williams et al., 1988 Gough et al., 1989). 

Plant cell culture originating from Cell Totipotency Theory was proposed by Haberlandt, a German botanist, in 1902. Plant cell secondary metabolites are widely used, have significant economic value, and can be made into medicines such as paclitaxel, ginsenosides, and artemisinin. The structures of... 

Plant cell cultures are an attractive alternative way to produce high-value secondary metabolites when compared to the whole plant (Ravishankar et al. 1999). Plant cells are biosynthetically totipotent, which means that each cell in culture retains complete genetic information, and hence it can produce the range of chemicals found in the parent plant. 

In order to produce secondary metabolic products from a plant, exogenous plant tissue instead of a whole plant, may be cultivated as a suspension culture in an aseptic condition. The technical rationale for using plant tissue is based on the unique biochemical totipotency of plant cells.8... 

Since plant tissue culture has become a potential biotechnological field, it is justified to investigate the past of this valuable tool. As early as 1839, Schwann suggested that plant cells should be considered totipotent. This means that each living cell of plant tissue is able to develop into a whole organism provided the cell is maintained in a proper environment, esp. with respect to nutrition. 

ES cells should be cultured on a feeder layer of inactivated embryonic fibroblasts (Robertson, 1987). Embryonic fibroblasts should be used within a week after inactivation. The ES cells should be split every second day (see below). It is important that the ES cells be trypsinized to obtain a single cell suspension to avoid differentiation. Totipotency in ES cells tends to be lost with passage number it is therefore advisable to subclone the cells each 20 passages to recover the full potentiality. 

Most of our studies have been carried out in Nicotiana silvestris, chosen for the following advantageous characteristics. It is a true diploid (2n=24). A background of basic classical genetics exists. It is self-fertile, flowers rapidly and produces numerous seeds. It has a relatively short life cycle. Haploids are readily obtained. It grows rapidly in suspension culture and is totipotent. Protoplast techniques have been developed and somatic-cell hybridization is feasible. 

For definitive testing of the totipotency concept, single cells or protoplasts must be picked axenically from the culture medium and placed on a suitable growing medium then through manipulation of the mineral, vitamin, amino acid, and hormonal components of the medium cause development of a tissue (usually callus) that gives rise to embryoids that in turn develop roots, stems. 

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