Project description:The success of plant pathogenic fungi mostly relies on their arsenal of virulence factors that are expressed and delivered into the host tissue during colonization. The biotrophic fungal pathogen Ustilago hordei causes covered smut disease on both barley and oat. The biotrophic interaction of the fungus with its host plant starts with formation of appressorium and subsequent penetration of invasive hyphae into the plant cell, in which the plasma membrane of the infected cell gets invaginated and encases the penetrating hypha. After penetration, the fungus grows towards and in later stages along the vascular bundles, which contain assimilates and metabolites, representing a source of nutrients for the fungus. In this study, we combined cytological, genomics and molecular biological methods to achieve a better understanding of the molecular interactions in the U. hordei-barley pathosystem. This study focuses on the genome-wide Agilent Microarray-based transcriptome analysis of U. hordei during early stages (20 hpi, 40 hpi, 3 dpi, 6 dpi) of the biotrophic interaction in comparison to axenic culture growth. This should give insights into the molecular processes during these stages by the identification of regulated genes. Furthermore, the regulation of putative secreted enzymes and effector proteins can be studied. Transcriptome analysis of U. hordei at different stages of host infection revealed 273 effector gene candidates with differentially expressed transcript levels. Furthermore, U. hordei transcriptionally activates core-effector genes that may suppress even non-host early defense responses. It could be shown that about one half of the U. hordei open reading frames are differentially regulated during at least one of the analyzed stages. Based on the transcriptome data, some of them were identified to be involved in stage-specific processes, e.g. in the nutrient acquisition by the induction of carbohydrate transporters during the later stages of infection. Furthermore, a set of strongly induced genes was identified, which encode for secreted proteins. The acquired datasets show a strong induction of stage-specific secreted effector proteins, whose functions remain unclear. Based on the expression values, a group of 16 promising candidates was chosen for functional characterization. The success of plant pathogenic fungi mostly relies on their arsenal of virulence factors that are expressed and delivered into the host tissue during colonization. The biotrophic fungal pathogen Ustilago hordei causes covered smut disease on both barley and oat. The biotrophic interaction of the fungus with its host plant starts with formation of appressorium and subsequent penetration of invasive hyphae into the plant cell, in which the plasma membrane of the infected cell gets invaginated and encases the penetrating hypha. After penetration, the fungus grows towards and in later stages along the vascular bundles, which contain assimilates and metabolites, representing a source of nutrients for the fungus. In this study, we combined cytological, genomics and molecular biological methods to achieve a better understanding of the molecular interactions in the U. hordei-barley pathosystem. This study focuses on the genome-wide Agilent Microarray-based transcriptome analysis of U. hordei during early stages (20 hpi, 40 hpi, 3 dpi, 6 dpi) of the biotrophic interaction in comparison to axenic culture growth. This should give insights into the molecular processes during these stages by the identification of regulated genes. Furthermore, the regulation of putative secreted enzymes and effector proteins can be studied. Transcriptome analysis of U. hordei at different stages of host infection revealed 273 effector gene candidates with differentially expressed transcript levels. Furthermore, U. hordei transcriptionally activates core-effector genes that may suppress even non-host early defense responses. It could be shown that about one half of the U. hordei open reading frames are differentially regulated during at least one of the analyzed stages. Based on the transcriptome data, some of them were identified to be involved in stage-specific processes, e.g. in the nutrient acquisition by the induction of carbohydrate transporters during the later stages of infection. Furthermore, a set of strongly induced genes was identified, which encode for secreted proteins.The acquired datasets show a strong induction of stage-specific secreted effector proteins, whose functions remain unclear. Based on the expression values, a group of 16 promising candidates was chosen for functional characterization.
Project description:Ustilago hordei is a basidiomycete fungus that infects barley and oats. It has a narrow host range and can infect only germinating seedlings. Symptoms do not occur until heading of the mature plants when the fungus has proliferated in meristematic tissue and replaces kernels with masses of black teliospores. Incompatibility is due to the presence of an avirulence effector product, UhAVR1, expressed in the fungus upon infection and secreted into the host, which is subsequently recognized by the barley plant resistance gene product RUH1 in cultivar Hannchen, leading to plant cell death, fungal growth arrest, and no disease. We have identified UhAvr1, and the transcriptome response of the barley plant to strains with and deleted for this gene was assessed using the 22K Affymetrix barley array. Incompatibility and cell death is apparent at 48 hrs after inoculation, so the transcriptome was assessed at this time point. For comparison, the transcriptome of barley cultivar Odessa, which lacks resistance gene Ruh1, during a compatible interaction was also assessed.