The Hypersensitive response (HR) is (nearly always) associated with resistance (see Collinge et al., 1994, Dangl, 1996). The mechanisms are poorly understood but the accumulation of specific transcripts is involved (e.g. Boudet for tobacco). Their function is unknown, and may well be downstream of the key event. The analysis of cell death mutants, which mimic the hypersensitive response will presumably shed some light on the mechanisms involved (Dangl, 1996).
Studies with transcriptional inhibitors (e.g. Carver with barley-powdery mildew - see Collinge et al., 1996) indicate that transcription is necessary.
The current, most widely accepted model for HR suggests that an oxidative burst is reponsible for the depolarization of the membrane (see Hammond-Kosack et al 1996 illustrated from barley and again). The mechanisms by which this occurs are not entirely clear, since contradictory evidence has been obtained fromdifferent systems - e.g. cereals seem to behave differently.
revised 13-09-01 Author dbc@kvl.dk