Cgl-SLT2 is required for appressorium formation, sporulation and pathogenicity in Colletotrichum gloeosporioide

The mitogen-activated protein (MAP) kinase pathways has been implicated in the pathogenicity of various pathogenic fungi and plays important roles in regulating pathogenicity-related morphogenesis. This work describes the isolation and characterization of MAP kinase gene, Cgl-SLT2, from Colletotrichum gloeosporioides. A DNA sequence, including 1,633 bp of Cgl-SLT2 open-reading frame and its promoter and terminator regions, was isolated via DNA walking and cloned. To analyze gene function, a gene disruption cassette containing hygromycin-resistant gene was constructed, and Cgl-SLT2 was inactivated via gene deletion. Analysis on Cgl-slt2 mutant revealed a defect in vegetative growth and sporulation as compared to the wild-type strain. When grown under nutrient-limiting conditions, hyperbranched hyphal morphology was observed in the mutant. Conidia induction for germination on rubber wax-coated hard surfaces revealed no differences in the percentage of conidial germination between the wild-type and Cgl-slt2 mutant. However, the percentage of appressorium formation in the mutant was greatly reduced. Bipolar germination in the mutant was higher than in the wild-type at 8-h post-induction. A pathogenicity assay revealed that the mutant was unable to infect either wounded or unwounded mangoes. These results suggest that the Cgl-SLT2 MAP kinase is required for C. gloeosporioides conidiation, polarized growth, appressorium formation and pathogenicity.

Ca~(2+) Signaling Pathway Involved in Bipolaris maydis Conidium Germination and Appressorium Formation / 微生物学通报

Bipolaris maydis, the causal agent of northern leaf blight of maize, forms a dome-shaped infection structure, an appressorium, to infect its host. To elucidate if calcium signaling pathway is correlated with conidium germination and appressorium formation of Bipolaris maydis induced by hydrophobic surface. Conidia were treated by three kinds of inhibitors. Microscopic examination and statistical data showed: (ⅰ)EGTA, a chelating agent selective for Ca~(2+), Verapamil which could block Ca~(2+) channels, KN93, a selective inhibitor of CaMK could inhibit germination and appressorium formation. (ⅱ)Under the same concentrations of inhibitors, appressorium formation was inhibited more strongly than conidium germination. These inhibitors caused the formation of small and abnormal appressorium. These results strongly suggested that Ca~(2+ )signaling pathway was involved in conidium germination and appressorium formation induced by hydrophobic surface.

A Review on Relations Between Pathogenicity and Melanin of Plant Fungi / 微生物学通报

Melanin is formed by oxidative polymerization of phenolic compounds,basically different kinds of melanin come from different organisms.DOPA melanin and DHN melanin have same physical and chemical characters although they have different biosynthetic pathway.DHN melanin is common in plant fungi and plays an important role on infection.The melanin accumulates in the fungal cell walls and prevents organic and inorganic molecules penetrating out,that insures appressorium's pressure and infection ability.This paper has reviewed the kinds and characters,especially discussed the role of melanin during pathogen infection based on our some research.