Using a temperature shift, from 33 C to 20 C, to initiate and synchronise the HR we have monitored presymptomatic infection foci by fluorescence, confocal and electron microscopy. Following cell death and necrotic lesion development virus infected cells are still present at the necrotic lesion margin, however, all remaining infected cells eventually die indicating that for this pathosystem the HR is a two phase process. In parallel studies aimed at investigating the induction of cell death in plants by the mammalian proapoptotic protein bax a number of similarities to the TMV-induced hypersensitive response were observed suggesting the possibility that bax could interact with components of the plant cell death machinery. Significantly the cytotoxic effect of bax required mitochondrial localisation raising the possibility that in plants, like animals, cell death signalling is transduced through mitochondria. 2 IACR-Long Ashton Research Station, Long Ashton, Bristol.
Colletotrichum species cause anthracnose on a wide range of plants.
Colletotrichum lindemuthianum is in the latter grouping, and aspects of spore adhesion, germination and appressorium development will be described as well as the formation of biotrophic and necrotrophic hyphae. Function of pili in molecular interaction of Pseudomonas syringae with the host plant Martin Romantschuk Viikki Biocenter, Department of Biosciences, Division of General Microbiology, PO Box 56, FIN-00014 University of Helsinki, Finland Pseudomonas syringae is an opportunistic plant pathogen which is capable of colonizing aerial plant surfaces and leaf tissue without causing disease symptoms. The bacterium possesses a variety of traits that makes it withstand the variable and harsh conditions on plant leaf surfaces. It is resistant to UV radiation, drought, and to dislocation by physical forces such as rain and wind. In dry conditions on the leaf surface clusters of bacteria are found encapsulated in extracellular polysaccharide.