ABSTRACT
The principle of direct transfer of genes consists of mixing plant cells with DNA in solution. The DNA is not necessarily a transformation vector and the transgenes can be DNA fragments, which are called "naked DNA". However, the cell wall in plants (and fungi) is an obstacle to the integration of DNA in cells. Therefore, it is necessary to prepare protoplasts by digestion of the pecto-cellulosic wall that will be mixed with the DNA in solution. The application of appropriate physicochemical conditions to this mixture causes a transitory and reversible permeabilization of the plasma membrane that allows DNA molecules to penetrate the protoplasts. These DNA molecules reach the nucleus-by a mechanism that is still unknown-and are integrated by recombination with chromosomes of the plant cell.
