title: Transcriptome analysis reveals new insight into appressorium formation and function in the rice blast fungus Magnaporthe oryzae.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: North Carolina State University, Center for Integrated Fungal Research, Raleigh, NC 27695-7251, USA. yoh2@ncsu.edu
authors.forename: Yeonyee
authors.initials: Y
authors.lastname: Oh
authors.forename: Nicole
authors.initials: N
authors.lastname: Donofrio
authors.forename: Huaqin
authors.initials: H
authors.lastname: Pan
authors.forename: Sean
authors.initials: S
authors.lastname: Coughlan
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Brown
authors.forename: Shaowu
authors.initials: S
authors.lastname: Meng
authors.forename: Thomas
authors.initials: T
authors.lastname: Mitchell
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Dean
mesh_terms: D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D050356:Lipid Metabolism; D020082:Magnaporthe / Q000166:cytology* / Q000235:genetics* / Q000502:physiology; D015398:Signal Transduction; D013172:Spores, Fungal / Q000166:cytology* / Q000235:genetics*
chemical_list: D005656:Fungal Proteins