Summary - Tissue Culture

Transformation is the step in the genetic engineering process where a new gene (transgene) is inserted into a single plant cell.
There are several things that must happen correctly for a cell to be successfully transformed:
1. The new gene must be delivered into the nucleus of a cell and insert into a chromosome.
2. The cells that receive the new gene must stay alive.
3. The cells and plants that contain the new gene must be easily identifiable (selectable markers).
4. The transformed cell must divide and give rise to an entire plant.
5. The location where the transgene inserts into the chromosome must not interfere with the expression of the gene.
6. The new gene must not insert into an existing gene in the chromosome that influences survival of the plant cell or productivity of the entire plant.
Tissue culture is when clusters of undifferentiated cells, called callus, are grown in culture.
The steps in tissue culture are:
1. Tissue samples are taken from a plant (explanting).
2. The samples are grown on media and masses of undifferentiated cells begin to grow.
3. The undifferentiated cells can be manipulated (procedures such as, DNA extraction and transformation with a transgene and selectable marker, can be done).
4. Growth hormones are added to the media causing the cells to multiply and differentiate into entire plants.
Genotype specificity - some crop lines are genetically more equipped to handle the stresses of tissue culture. Since these lines are typically lower yielding, older lines, once a plant is successfully transformed it must go through backcrossing to move the transgene into a high yielding, elite line.
Alternatives to tissue culture include transforming germline cells or pollen.
Selectable marker genes are genes that encode easily detectable traits. Selectable marker genes are co-transformed with another gene of interest into a plant cell making transgenic cells easy to select out from non-trangnic cells.