The expression of pathogen-related (PR-) proteins was measured by northern blot analysis in wounded and pathogen-challenged chestnut in vitro stems using heterologous probes. It showed that hypovirulent C. parasitica triggered PR-protein gene transcription strongly, but also that virulent C. parasitica and wounding caused an accumulation of PR-transcripts, although to a lesser extent.
Further investigations focussed on the wound response of chestnut and on the influence of pathogen infection on the expression of wound-responsive genes. Wound-responsive genes were isolated from chestnut stems by differential mRNA display and comprised genes involved in signalling, pathogen and stress response, growth regulation, protein metabolism, light and energy related genes and genes of unknown function. Comparison of the expression patterns of the isolated genes revealed that C. parasitica inoculation altered the expression of wound-responsive genes: Some groups, predominantly pathogen defence genes, e.g. beta-1.3-glucanase, were strongly induced when C. parasitica was applied to the wounds, whereas others, such as growth-regulating genes were highly expressed when the plants were only wounded and no fungal inoculum was present in the wound.