Potential risks of gene escape from transgenic crops through pollen and seed dispersal are being actively discussed and have slowed down full utilization of gene technology in crop improvement. To ban the transgene flow, barren zones and 'terminator' technology were developed as GMO risk management technologies in transgenic crops. Unfortunately, the technologies have not protected reliably the transgene migration to wild relatives. The present study offers a novel molecular technique to eliminate gene flow from transgenic plants to wild relatives by recoverable block of function (RBF). The RBF consists of a blocking sequence linked to the gene of interest and a recovering sequence, all in one transformable construct. The blocking sequence blocks a certain molecular or physiological function of the host plant. Action of the blocking sequence leads to the death of the host plant or to an alteration in its phenotype resulting in inability for sexual reproduction in nature. The recovering construct recovers the blocked function of the host plant. The recovering construct is regulated externally by a specific chemical or physical treatment of the plants and does not act under natural conditions. In nature, hybrids of the transgenic plants with its wild relatives carrying the RBF will die or be unable to reproduce because of the blocking construct action. A wet-king model of RBF is described in this report as one example of the RBF concept. This RBF example is based on ba, nase (the blocking construct) and barstar (the recovering construct) gene expression in tobacco under sulfhydryl endopeptidase (SH-EP) and a heat shock (HS) promoter, respectively.