INHIBITION OF FUNGAL DISEASE DEVELOPMENT IN PLANTS BY ENGINEERING CONTROLLED CELL-DEATH

We have tested a new strategy for engineering fungal disease resistanc e in crops which is based on inhibition of fungal growth and reproduct ion by controlled generation of necrotic lesions at infection sites, a nalogous to the naturally occurring hypersensitive cell death, The app roach relies on the use of two chimeric genes. On the one hand, a prom oter fragment of the potato prp1-1 gene which mediates rapid and local ized transcriptional activation selectively in response to pathogen at tack is used to drive the expression of the bacterial ribonuclease, ba rnase, On the other hand, transgenic plants express barstar, a specifi c inhibitor of barnase, to minimize the detrimental effects of potenti al background barnase synthesis in non-infected tissue. Sporulation of the late-blight fungus Phytophthora infestans was considerably reduce d on leaves from transgenic potato lines harboring this two-component system, Treatment of leaves from such plants with ethylene, a chemical stimulus of prp1-1 promoter activity, resulted in rapid tissue destru ction, indirectly indicating the inducibility and action of barnase, F urthermore, the reduction of fungal sporulation cosegregated,vith the transgenes in an F1 population,