EXPRESSION OF A SINGLE-CHAIN FV ANTIBODY AGAINST ABSCISIC-ACID CREATES A WILTY PHENOTYPE IN TRANSGENIC TOBACCO

The plant hormone abscisic acid (ABA) participates in the control of s everal important physiological processes in plants such as stomata reg ulation, seed dormancy and stress tolerance. A new strategy was develo ped to study these phenomena by blocking abscisic acid with intracellu larly expressed specific single-chain variable fragment (scFv) antibod ies. Here evidence is presented that the expression of single-chain Fv antibodies against abscisic acid in the endoplasmic reticulum of tran sgenic tobacco cells leads to a witty phenotype. Stomatal conductance is increased at high CO2 concentrations dependent on the level of anti body expression in leaves. Symptoms of abscisic acid deficiency were g enerated in the transformants although they have even higher levels of abscisic acid than wild-type plants.