COORDINATED ACTIVATION OF PROGRAMMED CELL-DEATH AND DEFENSE-MECHANISMS IN TRANSGENIC TOBACCO PLANTS EXPRESSING A BACTERIAL PROTON PUMP

In plants, programmed cell death is thought to be activated during the hypersensitive response to certain avirulent pathogens and in the cou rse of several differentiation processes. We describe a transgenic mod el system that mimics the activation of programmed cell death in highe r plants. In this system, expression of a bacterial proton pump in tra nsgenic tobacco plants activates a cell death pathway that may be simi lar to that triggered by recognition of an incompatible pathogen. Thus , spontaneous lesions that resemble hypersensitive response lesions ar e formed, multiple defense mechanisms are apparently activated, and sy stemic resistance is induced in the absence of a pathogen. Interesting ly, mutation of a single amino acid in the putative channel of this pr oton pump renders it inactive with respect to lesion formation and ind uction of resistance to pathogen challenge. This transgenic model syst em may provide insights into the mechanisms involved in mediating cell death in higher plants. In addition, it may also be used as a general agronomic tool to enhance disease protection.