Establishment of cell-specifically inducible expression systems in transgenic barley and maize

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Experimental approaches to over-expression or knock-down of genes implicated in plant pathosystems using constitutive or tissue-specific promoters often result in pleiotrophic effects such as developmental aberrations or reduced viability. Hence, the immediate gene function confined to the context of plant-pathogen interaction cannot be studied properly using these conventional expression systems in transgenic plants. Thus, this project aims at establishing gene expression systems in barley and maize based on the ethanol-inducible AlcRlalcA promoter system derived from Aspergillus nidulans. This two-component system provides control of transgene expression at three levels: (1) the transactivator gene AlcR can be driven by an appropriate cell-specific promoter, (2) the inducing agent can be applied at any developmental stage of choice, and (3) locally confined to only a part of the plant investigated. Two candidate promoters specific for highly relevant tissues in plant-pathogen interactions will be functionally verified first by Agrobacterium-mediated transformation of barley using conventional reporter gene constructs. These promoters will then be used in conjunction with the transactivator AlcR to develop cell-specifically inducible expression systems. In parallel we will establish genetic transformation of maize via infection of either immature embryos or androgenetic pollen cultures with Agrobacteria. Eventually, it is envisaged to provide a proof of concept by transformation of barley and maize using the cell-specifically inducible expression systems with the alcA promoter driving the GFP gene. In various follow-up approaches, the established systems will be highly valuable for functional characterisation of genes putatively implicated in the compatible interaction of barley or maize with various pathogenic or mutualistic fungi.