Redirection of photoassimilate partitioning by biotrophic, hemibiotrophic and mutualistic fungi through altered transporter gene expression

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Allocation and distribution of carbohydrates, amino acids, ions, water and numerous other compounds is tightly regulated in higher plants. It is essential for sufficient and timely supply of these compounds to multiple sinks that continuously change in strength and number during development and in response to environmental factors. During plant-pathogen interactions the formation of new sink tissues is triggered by the pathogen that aims to participate in the host s pool of photoassimilates. The signal transduction mechanisms underlying these changes in transporter gene expression are largely unknown. The aim of this project is the identification and characterization of host target genes responsible for altered assimilate partitioning and of fungal transport proteins regulated during host/fungus interaction. To this end, plants from three different species (barley, Arabidopsis, maize) will be infected with a pathogenic (Blumeria - barley [B2]; Erysiphe - Arabidopsis; Ustilago [A2] and Colletotrichum [A1] - maize) and a mutualistic fungus (Piriformospora [B2] for all three species) and with apathogenic fungal mutants, where available (Ustilago, A2). Altered levels of transporter gene transcripts will be identified (microarray analyses) and will be separated into unique (plant and/or plant-pathogen specific) and ubiquitous changes. The effect of overexpression or of reduced expression (RNAi) of these genes on fungal infection in wild type and mutant plants (Arabidopsis) will be analyzed. Fungal transporter genes (Colletotrichum) will be identified from different stages of the interaction [A1] and their role for fungal growth will be analyzed.