Cloning of genes by mRNA differential display induced during the hypersensitive reaction of soybean after inoculation with Pseudomonas syringae pv. glycinea.

Soybean (Glycine max [L.] Merr.) cell suspension cultures (cv. Williams 82) inoculated with the pathogenic bacteria Pseudomonas syringae pv. glycinea respond with a hypersensitive reaction (HR) when the bacteria express the avirulence gene avrA. A mRNA differential display was established for this system to allow the identification of genes induced during the HR. Six PCR-fragments (DD1-DD6) from the differential display analysis were identified, which are induced during the HR. Database searches revealed that the fragment DD1 encodes chalcone isomerase and DD2 was identified as ubiquitin. The fragment DD3 shares significant homology to the signalling molecule 14-3-3. The partial DD4 product is homologous to the enhancer of rudimentary from Drosophila and an uncharacterized homologue of it from Arabidopsis. The fragment DD5 is similar to glucose-6-phosphate dehydrogenase which provides NADPH to the cell. The PCR-product DD6 seems to be a new leucine-rich-repeat disease resistance gene from soybean, which is significantly induced during the HR. All of the identified genes are clearly induced during a HR in infected plants of the same cultivar, indicating that results from the cell culture model system can be transferred to intact plants. These studies show that complex mRNA differential display is a powerful tool to identify new induced gene in plant-pathogen interactions.