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Peroxisomal carnitine acetyl transferase is required for elaboration of…

- - - - Bounded by a melanin-rich
        cell wall
      - Accumulates glycerol to very high concentrations
    - - Regulated
        by the cAMP response pathway
  - - - Convert acetyl
        CoA units to acetyl-carnitine for transport across the membrane
      - PTH2, as potentially
        encoding a CAT
        
        Pth2 is regulated
        by the cyclic AMP response pathway
        
        Located in
        peroxisomes
        
        Lipid reserve mobilization during
        appressorium maturation
        
        Penetration
        hypha formation and host invasion
- - - - Protein extracts were prepared by grinding 0.2 g of mycelium (wet weight).
      - with glass beads in 1 ml of 50 mM Tris·HCl (pH 7.5)
      - and centrifuging the resulting slurry at maximum
      - speed in a microcentrifuge for 1 min.
  - - - the sGFP coding sequence was removed from pMJK80
      - and inserted before the penultimate codon of PTH2 ensuring the integrity of the SKL peroxisomal targeting sequence.
- - - - this is indicating that PTH2 is not needed for generation or maintenance of appressorium turgor
  - - - Large numbers of lipid bodies were present within conidia, germ tubes and developing appressoria of Guy 11
      - lipid bodies were predominantly mobilized to appressoria after 8 hrs
      - between 12 and 24 h, lipid bodies became depleted
        at the onset of turgor generation
      - in pth2 mutant, a few lipid bodies presence in appressoria after 8hr
    - - Quantitative revealed the large number of lipid bodies in germ tube of pth2 mutants after 24hrs incubation
  - - - the ability cause rice blast symptoms was partly restored to pth2 mutants
      - the mutant was still reduced in disease
        lesion formation when compared with the wild-type strain
      - lipid mobilization to the appressorium in pth2 mutant also restored to the normal level
      - it seems like the glucose take up by the fungus can partly restore the functional competence of appressoria
  - - - Vegetative hyphae of pth2 mutants stained normally with calcofluor white
      - These findings provide
        evidence that chitin synthesis during invasive hypha formation is impaired in the Dpth2 mutant
- - - - Cat2 provides for peroxisomally generated acetyl CoA to transfer to the cytoplasm
      - Cat1 channels acetyl CoA into mitochondria for oxidation via the tricarboxylic acid cycle
  - - - 2nd- PTH2 is involved in the supply of acetate units for melanin biosynthesis via the dihydroxynaphthalene pathway
        
        Although there is a reduction in melanization, this is not the primary reason for loss of pathogenicity in Dpth2
        
        1st- both light and electron microscopy confirmed appressorial melanin biosynthesis does occur in Dpth2 mutants
        
        2nd-Appressorium turgor generation was normal in Dpth2 mutants
        
        3rd-Addition of a melanin biosynthesis intermediate, scytalone, failed to restore lesion formation in Dpth2 mutants
        
        Concluded that although Pth2 activity very likely contributes to melanin biosynthesis
        
        Dpth2 mutants showed a reduction in melanin production in appressoria when observed by electron microscopy
        
        Evidence showed appressorium melanization is vital for plant infection by M. grisea
        
        CAT is not essential for turgor generation in appressoria.
      - 1st- Pth2 is required for turgor generation necessary for appressorium-mediated penetration
        
        which is necessary for turgor generation
        
        Cytorrhysis assays shows no observable difference in appressorium turgor in Dpth2 mutants
        
        to yield precursors to glycerol biosynthesis
        
        Acetyl CoA from fatty acid b-oxidation could be processed via the glyoxylate cycle and gluconeogenesis
    - - therefore set out explore the likely roles of Pth2 in plant infection by M. grisea