Chemical catalysts

A number of promoters are now known (several already patented), which respond to chemical inducers. As many as 29 traitor technology patents, issued during 1998, all involved 'inducible promoters' that would respond to external chemical stimuli.

There are both negative and positive aspects of the use of these inducible promoters in transgenic crops.

This technology, if ever used in future, will though increase the profits of seed companies by forcing the farmers to buy their proprietary chemicals (e.g. an insecticide/herbicide manufactured by the same company) along with the seed, but the seed company will not be .able to sell this package of seed + chemical, if the net profit earned by the farmer is not more than what he earns by growing the existing varieties.

For instance, PR-la promoter drives expression of a defence gene, and is induced by pathogen attack, oxidative stress and leaf senescence. But it also responds to benzothiadiazole (BTH) and INA (isonicotinic acid).

If Bt gene for o-endotoxin is combined with PR-Ia, the expression of the gene will be induced only by spraying BTH or INA. Such a use of inducible promoter will be desirable because constitutive expression of δ-endotoxin may favour adaptive process of a pathogen.

We only hope that the seed companies will make use of inducible promoters in a manner, which serves the farmers and also meets their commercial objectives.