Project description:Cytosine methylation is an important epigenetic modification of DNA that is involved in genome defense and transcriptional regulation in eukaryotes. Despite extensive efforts to understand genome-wide distribution and function of DNA methylation in mammals and plants, contribution of DNA methylation to biology of microbial eukaryotes is largely unknown to date. Here we used genetic manipulations and high-throughput bisulphite sequencing on the model plant pathogenic fungus, Magnaporthe oryzae to elucidate the dynamics and mechanics of DNA methylation during pathogenic development.
Project description:Cytosine methylation is an important epigenetic modification of DNA that is involved in genome defense and transcriptional regulation in eukaryotes. Contribution of DNA methylation to biology of microbial eukaryotes is largely unknown to date. Here we used RNA-seq to examine the impact of DNA methylation on transcriptional output in the genome of a model pathogenic fungus, Magnaporthe oryzae by comparing expression profiles of wild-type and methylation-deficient mutant strains.
Project description:The nucleolus has emerged as a central hub for nuclear functions in eukaryotes. Studies in mammals and the model yeast Saccharomyces cerevisiae showed that the nucleolus is pivotal to nuclear functions other than ribosome biogenesis. Importantly, rDNA transcription and ribosome assembly were shown to positively correlate with the size of the nucleolus. However, little is known about the nucleolus of filamentous fungi. Here, we investigated how the size and shape of nucleolus in the plant pathogenic filamentous fungus, Magnaporthe oryzae, respond to nutrient conditions and infection-related development by monitoring the nucleolar marker protein, MoNOP1 tagged with red fluorescent protein (MoNOP1-RFP). Our work revealed that in the hyphae of M. oryzae, the nucleolar size is decoupled from the nucleolar activity under low nutrient condition. A complete lack of carbon or nitrogen did not cause such decoupling. In conidia, no or faint RFP signals were initially observed, hinting at the absence of functional nucleoli. RFP signals only started to become visible in conidia within 2 hours of germination when the germ tube tip began to differentiate a specialized infection structure, the appressorium. RFP signals diminished thereafter. In contrast, in the appressorium, signals became concentrated after 6 hours as the appressorium matured. We propose that such nucleolar dynamics may reflect the strategy of filamentous fungi under low nutrient availability to forage for food resources as well as the roles of the nucleolus during fungal development. IMPORTANCE The nucleolus is a dynamic subnuclear structure that is involved in many fundamental processes of the nucleus. In higher eukaryotic cells, the size and shape of nucleoli correlate with nucleolar activities. For fungi, knowledge of the nucleolus and its functions is primarily gleaned from budding yeast. Whether such correlation is conserved and how nucleolar functions are regulated in filamentous fungi including important human and crop pathogens are largely unknown. Our observations reveal that the dynamics of nucleolus in a model plant pathogenic fungus, Magnaporthe oryzae, is distinct from those of animal and yeast nucleoli under low nutrient availability and during pathogenic development. Our data not only provide new insight into the nucleoli in filamentous fungi but also highlight the need for investigating how nucleolar dynamics is regulated in comparison to other eukaryotes.
Project description:To investigate plant-fungus interactions in early stage of infection, we analyzed response of rice against Magnaporthe grisea infection deficient mutants. In M. grisea, Mgb1 and Mst12 are essential for development of infection structures. Deletion of MGB1 results in defect in appresorium formation, and MST12, in penetration peg development. Analysis of gene expression profiles in rice by microarray revealed the mutant-specific and R gene dependent gene expression, strongly suggesting that gene-for-gene interaction commences before the penetration into rice cell. Keywords: disease state analysis
Project description:A cell death pathway, ferroptosis, occurs in conidial cells and is critical for formation and function of the infection structure, the appressorium, in the rice blast fungus Magnaporthe oryzae. In this study, we identified an orthologous lysophosphatidic acid acyltransferase (Lpaat) acting at upstream of phosphatidylethanolamines (PEs) biosynthesis and which is required for such fungal ferroptosis and pathogenicity. Two PE species, DOPE and SLPE, that depend on Lpaat function for production were sufficient for induction of lipid peroxidation and the consequent ferroptosis, thus positively regulating fungal pathogenicity. On the other hand, both DOPE and SLPE positively regulated autophagy. Loss of the LPAAT gene led to a decrease in the lipidated form of the autophagy protein Atg8, which is probably responsible for the autophagy defect of the lpaatΔ mutant. GFP-Lpaat was mostly localized on the membrane of lipid droplets (LDs) that were stained by the fluorescent dye monodansylpentane (MDH), suggesting that LDs serve as a source of lipids for membrane PE biosynthesis and probably as a membrane source of autophagosome. Overall, our results reveal novel intracellular membrane-bound organelle dynamics based on Lpaat-mediated lipid metabolism, providing a temporal and spatial link of ferroptosis and autophagy.
Project description:Parent-specific differentially methylated regions (DMRs) are established during gametogenesis and regulate parent-specific expression of imprinted genes. Monoallelic expression of imprinted genes is essential for development, suggesting that imprints are faithfully maintained in embryos and adults. To test this hypothesis, we targeted a reporter for genomic methylation to the imprinted Dlk1-Dio3 intergenic DMR (IG-DMR) to assess the methylation of both parental alleles at single-cell resolution. Biallelic gain or loss of IG-DMR methylation occurred in a small fraction of mouse embryonic stem cells, significantly affecting developmental potency. Mice carrying the reporter in either parental allele showed striking parent-specific changes in IG-DMR methylation, causing substantial and consistent tissue- and cell-type-dependent signatures in embryos and postnatal animals. Furthermore, dynamics in DNA methylation persisted during adult neurogenesis, resulting in inter-individual diversity. This substantial cell-cell DNA methylation heterogeneity implies that dynamic DNA methylation variations in the adult may be of functional importance.
Project description:Fungal diseases cause enormous crop losses, but defining the nutrient conditions encountered by the pathogen remains elusive. Here, we generated a mutant strain of the devastating rice pathogen Magnaporthe oryzae impaired for de novo methionine biosynthesis. The resulting methionine-requiring strain grew strongly on synthetic minimal media supplemented with methionine, aspartate or complex mixtures of partially digested proteins, but could not establish disease in rice leaves. Live-cell-imaging showed the mutant could produce normal appressoria and enter host cells but failed to develop, indicating the availability or accessibility of aspartate and methionine is limited in the plant. This is the first report to demonstrate the utility of combining biochemical genetics, plate growth tests and live-cell-imaging to indicate what nutrients might not be readily available to the fungal pathogen in rice host cells.