THE HYPERSENSITIVE RESPONSE - A PROGRAMMED CELL-DEATH ASSOCIATED WITHPLANT-RESISTANCE

In plants, the hypersensitive response (HR) is defined as a rapid cell death occurring in response to pathogen attack, and is closely relate d to active resistance. Initiation of the HR process begins with the r ecognition of the pathogen by the plant, which is mediated mainly by t he pathogen avirulence genes and the plant resistance genes. Then, com plex signal transduction pathways intervene, involving changes in prot ein phosphorylation, production of reactive oxygen species and modific ation of ion fluxes. Components required for the regulation of the HR cell death are now being identified genetically by the isolation of mu tants, in contrast to those involved in the execution of the cell deat h programme, which are still largely unknown. Further genetic and bioc hemical analyses will undoubtedly answer the question as to whether th is form of programmed cell death (PCD) can be compared with other form s of PCD in plants and with apoptosis in animals. (C) Academie des sci ences/Elsevier, Paris.