Gene Expression and the Control of Cell Differentiation
The cells of a developing organism can synthesize different proteins and diverge in structure and function even though they share a common genome. If a mature cell removed from a root or leaf can dedifferentiate in tissue culture and give rise to the diverse cell types of a plant, then it must pos- sess all the genes necessary to make any kind of cell in the plant (see Figure 20.15). Therefore, cell differentiation de- pends, to a large degree, on the control of gene expression— the regulation of transcription and translation, resulting in the production of specific proteins.
Evidence suggests that the activation or inactivation of specific genes involved in cell differentiation results largely from cell-to-cell communication. Cells receive information about how they should specialize from neighboring cells. For example, two cell types arise in the root epidermis of Arabidopsis: root hair cells and hairless epidermal cells. Cell fate is associated with the position of the epidermal cells.