Peroxisomal carnitine acetyl transferase is required for elaboration of penetration hyphae during plant infection by Magnaporthe grisea

Abstract

SummaryMagnaporthe grisea, the causal agent of rice blast disease, invades plant tissue due to the action of specialized infection structures called appressoria, which are used to breach the leaf cuticle and allow development of intracellular, infectious hyphae. In this report we demonstrate that peroxisomal carnitine acetyl transferase (CAT) activity is necessary for appressorium function, and in particular, for the elaboration of primary penetration hyphae. The major CAT activity in M. grisea is encoded by the PTH2 gene, which shows elevated expression in response to acetate and lipid, and is regulated by the cyclic AMP response pathway. Furthermore, a Pth2-GFP fusion protein colocalizes with a peroxisomal marker protein. Targeted deletion of PTH2, generated mutants that were completely non-pathogenic, lacked CAT activity and were unable to utilize a range of lipid substrates. The impairment of appressorium function in Dpth2 was associated with a delay in lipid reserve mobilization from germ tubes into developing infection cells, and abnormal chitin distribution in infection structures. Addition of glucose to Dpth2 mutants partially restored the ability to cause rice blast disease and lipid reserve mobilization. Taken together, our findings provide evidence that Pth2 plays a role in the generation of acetyl CoA pools necessary for appressorium function and rapid elaboration of penetration hyphae during host infection.

Peroxisomal and Mitochondrial β-Oxidation Pathways Influence the Virulence of the Pathogenic Fungus Cryptococcus neoformans

“…Defects in ␤-oxidation compromise virulence in phytopathogenic fungi (2,31,32,61,81; see also the accompanying article by Kretschmer et al [33a]). For example, we previously demonstrated that a mutant lacking the multifunctional enzyme Mfe2 in the basidiomycete Ustilago maydis had reduced virulence and sporulation on maize (32).…”

The Tig1 Histone Deacetylase Complex Regulates Infectious Growth in the Rice Blast Fungus Magnaporthe oryzae

“…Fungal growth and conidiation were observed after incubation for 2 to 3 d. For staining with DAB (Sigma-Aldrich), rice leaf sheath samples were incubated in 1 mg/mL DAB solution, pH 3.8, for 8 h and destained with ethanol/acetic acid (94/4, v/v) for 1 h before examination. For aniline blue staining (Bhambra et al, 2006), barley leaves were sampled 72 h after inoculation and incubated in 1 M KOH at 708C for 20 min. After washing three times with water and once with 67 mM K 2 HPO 4 , pH 9.0, the samples were stained with 0.05% aniline blue and examined with a Nikon epifluorescence microscope.…”

Peroxisome Function Regulates Growth on Glucose in the Basidiomycete Fungus Cryptococcus neoformans

“…Deletion of pex6 in the fungus Colletotrichum lagenarium reduces disease on bean leaves by impairing appressorium function during the initial stages of infection (36). Recently, a PEX6 homolog and a peroxisome-targeted acetyltransferase have been shown to be required for appressorium formation and pathogenicity of the major rice pathogen Magnaporthe grisea (4,60). Similarly, hex1 mutations impair appressorium formation in M. grisea (68).…”