A REPRESSION SYSTEM FOR GENES ENCODING PROTEINS TOXIC TO BACTERIA IN AGROBACTERIUM-TUMEFACIENS-MEDIATED PLANT TRANSFORMATION

Transfer of a chimeric gene encoding secretory T4 lysozyme under the c ontrol of the mannopine synthase promoter (pMAS) into tobacco by Agrob acterium-mediated gene transfer has proven to be difficult, This can b e due to unwanted expression of the lysozyme gene inserted into the T- DNA in Agrobacterium tumefaciens. Two different strategies have been s uccessfully tested to inhibit expression of foreign genes in bacteria using the T4 lysozyme gene as a model system: (a) cloning of the TAC p romoter in anti-orientation to the respective gene inside the T-DNA, a nd (b) insertion of an antisense T4 lysozyme gene under the control of the TAC promoter outside of the T-DNA. Transformation frequencies com parable to controls lacking the T4 lysozyme gene could be achieved whe n testing potato transformation using both approaches, These strategie s might also be useful for the transfer of other genes encoding compou nds with detrimental effects to bacteria. (C) 1998 Elsevier Science B. V. All rights reserved.