Expression of horseradish peroxidase in transgenic tobacco.

Introduction Peroxidases are common oxidoreductases present in plants, animals and micro-organisms. Plant peroxidases are classified as basic, neutral or acidic enzymes, depending on their profiles of elution during ion-exchange column chromatography or isoelectric points [ 11. Horseradish (Amtoru~h rusticuna) peroxidases (HRPs; EC 1.1 1.1.7), are probably the best characterized of these enzymes. They are believed to be involved in plant responses to a number of biotic and abiotic stresses, notably in the disruption of free radicals and active derivatives of oxygen. The effects of these molecules have been well described [2], and in general the presence of these compounds are ‘highly destructive’ for cell metabolism. However, these oxygen derivatives are involved in halogenation and hydroxylation reactions in peroxisomes and in the cell wall, suggesting that the plant cell needs a fine regulation between production and destruction of oxygen radicals. A key to the comprehension of the role of peroxidase activity in this and other stress responses could be the study of the effect of modified expression and targeting of peroxidase activity in transgenic plants. The present report describes the production of such tobacco plants using a synthetic HRP gene [ 31, with a range of regulatory and targeting sequences.