In contrast, the artificially programmed cell death is so designed as to cover all the races of a pathogen and possibly, more than one pathogen as well. There are two schemes for artificial cell death, viz.,
(1) two-component and
(2) single-component systems.
The single-component system is based on the expression of a toxic polypeptide in response to pathogen infection. The transgenes usable in this scheme may be those that encode toxins, ribonucleases, or other enzymes, whose products are toxic to plant cells.
The barnase gene from Bacillus amyloliquefaciens was placed under the control of infection specific promoter prp1-1and was transferred into potato. Transgenic potatoes showed effective control of Phytophthora infestans. Promoter prp1-1j ensures the expression of barnase gene in such cells that are infected by a fungal pathogen.
Synthesis of Barnase protein, an RNase, in such cells leads to their death; the pathogen would also die along with the dying host cells. Obviously, the strategy of artificially programme cell death will be effective against obligate parasites, but not against facultative parasites; in fact, facultative parasites may be pleased to use it to their own advantage.
