Construction of a heat‐inducible chimaeric gene to increase the cytokinin content in transgenic plant tissue

Abstract

The ipt gene of Agrobacterium tumefaciens T‐DNA encodes an isopentenyltransferase which causes cytokinin overproduction and developmental alterations in transformed plants. A chimaeric gene constructed by positioning the ipt coding region under the control of the hsp70 gene from Drosophila melanogaster allows heat‐regulated expression in transgenic plant tissue. Heat‐shock treatment of tobacco calli transgenic for the chimaeric hsipt gene increases the endogenous cytokinin concentration and enables these calli to grow on cytokinin‐free medium. Transgenic plants regenerated from calli transformed with the hsipt gene and grown at normal temperature are phenotypically normal.