K HAHLBROCK, O BATZ, J HAGEMEIER, E KOOPMANN and E LOGEMANN

Max-Pianck lnstitut for Zuchtungsforschung, Carl-von-Linne-Weg 10, D-50829 Koln, Germany

The large diversity of potential plant-pathogen interactions occurring at the whole-organism level is mirrored at the molecular level by a multitude of reactions involved in the sequential steps of recognition, signal transduction, gene expression and product accumulation. In fact. it seems that a challenged plant cell undergoes more or less total reprogramming of its metabolic activity [1].

The induced shift in metabolism includes a complex mechanism of signal perception and signal conversion in the plant cell membrane. Within a few minutes, these processes trigger, via a network of intracellular signalling cascades, numerous alterations in gene activity. These in turn are rapidly followed by corresponding changes in metabolic activities, including those leading to secondary product accumulation [1].

Results from studies of two particularly well-suited model systems, Petroselinum crispum and Arabidopsis thaliana, will be presented. In both cases, the large complexity of the overall response was observed at all levels: timing of the induced changes, spatial distribution, and structural and functional variations among the multitude of either transiently or stably accumulating products.

References
1. Somssich IE, Hahlbrock K, 1998. Trends Plant Science (in press).