Plants are constantly exposed to different abiotic and biotic stresses during their lifetime. Among the most important stress factors are pathogenic microorganisms causing diseases. This has lead to the development of elaborate resistance mechanisms by plants and sophisticated virulence mechanism by pathogens during their co-evolution. The exploitation of  disease-resistance mechanisms leading to durable protection is one major objectives of centemporary plant breeding and biotechnology. However, in order to achieve this goal much has yet to be learned about molecular plant-pathogen interactions, with special emphasis on pathogen effectors and quantitative  resistance controlled by multiple QTL.

The group Transcriptome Analysis is aiming at discovering genes and alleles in barley and wheat for resistance against major fungal diseases, with special emphasis on the barley powdery mildew fungus Blumeria graminis, by using approaches of functional genomics.

We have established an EST database from Blumeria-attacked barley epidermis in order to characterize the transcriptional response of this important tissue, which directly interacts with the majority of pathogenic fungi that exhibit a direct mode of penetration. Complex cDNA arrays that contain 10,450 and 13,000 unigenes, respectively,  from 26 cDNA libraries of barley have been developed in a joint effort of the Plant Genome Resources Centre (PGRC), and these have been used to analyse the transcriptome of host and nonhost plants.

We furthermore developed biolistic test systems based on transient gene expression in barley or wheat leaves that allow addressing gene function in plant disease resistance. These test systems are amenable for high throughput and include overexpression of foreign or host genes, as well as transient-induced gene silencing (TIGS) by RNAi. The transient single-cell expression systems take advantage of the fact that the interaction between Blumeria graminis and attacked host cells is largely a cell-autonomous event. Therefore, the outcome of interactions of transformed epidermal cells transiently expressing transgene constructs attacked by Blumeria graminis can be rapidly scored under a light microscope. Transformed epidermal cells can be identified by co-transformation of test-constructs with a reporter gene such as ß-Glucuronidase (Figure). So far we have tested approximately 1,000 candidate genes for a possible role in nonhost resistance against the wheat powdery mildew or in basal host  resistance against the barley powdery mildew. Microscopic analysis including pattern recognition has been fully automated in collaboration with the Bioinformatics Centre Gatersleben-Halle (BMBF).