Oh, Y. et al. Transcriptome analysis reveals new insight into appressorium formation and function in the rice blast fungus Magnaporthe oryzae. Genome Biol. 9, R85

North Carolina State University, Center for Integrated Fungal Research, Raleigh, NC 27695-7251, USA.
Genome biology (Impact Factor: 10.81). 02/2008; 9(5):R85. DOI: 10.1186/gb-2008-9-5-r85
Source: PubMed


Rice blast disease is caused by the filamentous Ascomycetous fungus Magnaporthe oryzae and results in significant annual rice yield losses worldwide. Infection by this and many other fungal plant pathogens requires the development of a specialized infection cell called an appressorium. The molecular processes regulating appressorium formation are incompletely understood.
We analyzed genome-wide gene expression changes during spore germination and appressorium formation on a hydrophobic surface compared to induction by cAMP. During spore germination, 2,154 (approximately 21%) genes showed differential expression, with the majority being up-regulated. During appressorium formation, 357 genes were differentially expressed in response to both stimuli. These genes, which we refer to as appressorium consensus genes, were functionally grouped into Gene Ontology categories. Overall, we found a significant decrease in expression of genes involved in protein synthesis. Conversely, expression of genes associated with protein and amino acid degradation, lipid metabolism, secondary metabolism and cellular transportation exhibited a dramatic increase. We functionally characterized several differentially regulated genes, including a subtilisin protease (SPM1) and a NAD specific glutamate dehydrogenase (Mgd1), by targeted gene disruption. These studies revealed hitherto unknown findings that protein degradation and amino acid metabolism are essential for appressorium formation and subsequent infection.
We present the first comprehensive genome-wide transcript profile study and functional analysis of infection structure formation by a fungal plant pathogen. Our data provide novel insight into the underlying molecular mechanisms that will directly benefit efforts to identify fungal pathogenicity factors and aid the development of new disease management strategies.

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    • "This pathway is fungus specific, and the ergosterol is required for the generation of a major constituent of the fungal plasma membrane (Parks and Casey 1995). The ergosterol biosynthesis is via the mevalonate pathway, in which the ERG13 (HMG-CoA synthase) and HMG1 (HMG-CoA reductase) catalyze two key consecutive steps for the conversion of acetoacetyl-CoA to HMG-CoA and HMG-CoA to mevalonate, respectively (Oh et al. 2008). As critical components of cell membranes of all eukaryotic organisms, steroid is required for the regulation of membrane fluidity and permeability (Lepesheva and Waterman 2007). "
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    • "No such expression pattern was not observed for transcripts encoding CRN proteins, suggesting different roles for these two classes of cytoplasmic effectors. Previous studies reported the detection of transcripts encoding secreted effectors in appressoria from Phytophthora species such as P. infestans, P. sojae, and P. capsici and in appressoria from ascomycetes, such as Magnaporthe grisea and Colletotrichum higginsianum [19, 21, 40, 41]. However, the secretion of Phytophthora cytoplasmic effectors has been documented only in haustoria to date. "
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    • "). Furthermore, several of these transporters are up-regulated during appressorium formation (Oh et al., 2008), under stress treatments or in planta (Mathioni et al., 2011), and are required for pathogenicity (Urban et al., 1999; Sun et al., 2006; Patkar et al., 2012b), possibly to protect against the buildup of peroxides and oxidative damage (Sun et al., 2006). Given our concerns over H 2 DCFDA localization and specificity , we also examined the more sensitive, specific and photostable long-wavelength ROS probe CRDR. "
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