Project description:Sirtuin is considered to play a significant role in the growth phase-dependent gene expression. In this study, we characterized sirtuin in the white koji fungus, Aspergillus kawachii, to examine their role on regulation of amylolytic enzymes and citric acid productions during the solid-state culture (koji). Characterization of rice-koji made using five putative sirtuin gene disruptants indicated that they are involved in amylolytic activity and acidity of rice koji; especially the sirD disruptant showed lower levels of α-amylase activity and citric acid production per mycelial weight in the koji compared the control strain. In addition, the sirD disruptant also showed a change in mycelial pigmentation, higher sensitivity to cell wall biogenesis inhibitor such as calcofluor white and Congo red, and reduced conidia formation, indicating that SirD is required for secondary metabolism, cell wall integrity, and conidial development. The cap analysis gene expression (CAGE) indicated that the transcriptional changes related to the characteristic phenotype of the sirD disruptant (e.g., a reduced transcript level of acid-stable α-amylase gene and a citric acid exporter) in rice koji. These results indicated that SirD has a significant role on the global transcriptional regulation including productions of α-amylase and citric acid in A. kawachii during the solid-state fermentation process.
Project description:Rice blast caused by Magnaporthe oryzae is the most devastating disease of cultivated rice. Several protein kinase cascades have been known to be essential to pathogenesis or important for response to stress, mycelial growth and conidiation in M. oryzae. However, phosphoproteins and their phosphorylation sites (p-sites) in this important fungal pathogen remain largely to be identified. In this study, 8087 phosphopeptides corresponding to 9825 p-sites from 1147 phosphoproteins were identified in mycelia of M. oryzae under a false discovery rate of < 0.55% at the peptide level. Notably, 33 previously reported pathogenesis-related proteins were included in the phosphoproteins at the mascot delta score 10. Further analyses of 581 motif-containing phosphoproteins that met more stringent criteria revealed that the phosphoproteins shared 19 distinct phosphorylation motifs, including the motif RxxpSP that was newly identified in this study but is widely distributed in diverse organisms. These phosphoproteins were mapped into 81 biological pathways. A total of 82 acidic motif-containing phosphoproteins were identified. Surprisingly, none of them except one were mapped to any of the metabolic pathways. Furthermore, a prediction disclosed a total of 174 kinase-substrate specific interactions in mycelia of M. oryzae. This study also detected phosphorylation of the tyrosine phosphatase Pmp1 and 7 other proteins upstream of Pmk1, but not Pmk1 and its downstream transcription factors. These results prompted a necessary revision of Pmk1 MAPK cascade, in which dephosphorylation of Pmk1 by Pmp1 in mycelia may block the activation of downstream targets.
Project description:The hemibiotrophic fungus Magnaporthe oryzae produces specialized biotrophic invasive hyphae (IH) that alter membrane structure and defense responses in invaded rice cells. IH successively invade live neighbor cells, apparently through plasmodesmata. Understanding fungal and rice genes that contribute to biotrophic invasion has been a challenge because so few plant cells have encountered IH at the earliest infection stages. Using a rice sheath inoculation method, we successfully enriched for infected tissue RNA that contained ~20% fungal RNA at a point when most IH were still growing in first-invaded rice cells. The RNAs were analyzed using the whole-genome M. oryzae oligoarray and a rice oligoarray. Rice genes that were induced >50-fold during infection were enriched for genes involved in transferring information from sensors to cellular responses. Fungal genes that were induced >50-fold in IH included the PWL2 avirulence gene and genes encoding hypothetical secreted proteins. The IH-specific secreted proteins are candidate effectors, proteins that the fungus secretes into live host cells to control cellular processes. Gene knock-out analyses of three putative effector genes failed to show major effects on pathogenicity. Details of the blast interaction transcriptome will provide insights on the mechanisms of biotrophic plant disease. Experiment Overall Design: Our goal was to compare expression in infected rice sheath to expression in mock inoculated rice, and to compare expression in biotrophic IH to expression in mycelium grown in nutrient medium. Using the rice microarray (Agilent Technologies), we analyzed samples from three biological replicates of rice leaf sheath at 36 hours after inoculation with the rice blast fungus M. oryzae. The same samples were used with the Agilent M. oryzae microarray (see series GSE8517). To estimate the ratio of fungal to rice RNAs in the infected sheaths, we compared RT-PCR amplification of fungal genes in infected tissue to amplification in standards produced by mixing known ratios of pure mycelial RNA with mock-inoculated rice RNA. Using this assay, fungal RNA content in infected tissues were approximately 20% of the total RNAs. We prepared control mixtures by pooling 20% mycelial RNA and 80% RNA from mock-inoculated rice sheath. Complementary RNAs from infected tissues were labeled with Cy3 or Cy5 and hybridized together with the control mixture RNA labeled with the other dye. Three independent biological replications were performed, with separate hybridizations for 2 technical replications and corresponding dye swap experiments. Data were analyzed by Rosetta Resolver® and showed a correlation of over 80% between biological replications.