POTATO GENES ACTIVATED BY INFECTION WITH PHYTOPHTHORA INFESTANS
T HAIZEL, M SCHNEIDER and JP METRAUX
Institute of Plant Biology, University of Fribourg, CH-1700 Fribourg, Switzerland
Background and objectives
The hypersensitive response (HR), a defence mechanism that involves rapid plant cell death, is associated with resistance and with the induction of systemic acquired resistance (SAR). We took advantage of the fact that, in tobacco, several genes have been described that are transcriptionally activated during HR of leaves infiltrated with an incompatible isolate of Pseudomonas solanacearum . Some of these genes might be related to HR itself or to resistance mechanisms that derive from it. If expressed under appropriate inducible promoters, such genes could lead to resistance. Potato homologues of these genes were therefore isolated for further characterization.
Materials and methods
For fungal induction experiments, leaves of 4-week-old potato plants were sprayed with P. infestans (strain 94-28) zoospore suspension (4000-5000 spores/ml) and harvested at different time points. Control plants were water-treated and harvested.
Results and conclusions
The two other genes are 72% identical but do not show any significant homologies with any gene present in the databases. Nevertheless, the expression of these two genes is different: while the first is constitutively expressed, the second exhibits a maximum induction 14 h after inoculation with P. infestans. Results from Southern blot analysis on potato genomic DNA suggest that these two genes belong to a multigene family. The function of these genes is yet to be found. However, their corresponding genomic clones have been isolated. Several promoter-reporter gene constructs have been generated for further study of the regulation and expression of these genes. Potato plants transformed with these constructs are currently being analysed.