The hypersensitive reaction of higher plants to viruses: a molecular approach

The molecular basis of necrosis and localization, the two fundamental processes involved in plant hypersensitivity, are critically examined. Cell death, followed by visible necrosis, is discussed in relation to: (i) the role of wounding; (ii) the possible occurrence of signal molecules; (iii) the series of biochemical events leading to necrosis; and (iv) the events restricting the necrotic lesion within a limited area. Localization of virus infection is considered as a consequence of two events, (i) the synthesis of antiviral factors around the lesion, and (ii) the inhibition of the synthesis of the protein responsible for cell-to-cell spread of virus infection. The present knowledge, however, supplies only poor information on both the first events of cell-virus interaction and the chemical nature and role of putative signal molecules.