The “double-edged sword” model of cell death.

<p>Self-activated (programmed) cell death (<b>red</b> arrows) results in elimination of a small number of cells, effectively blocking the spread of “non-killer” pathogens (<b>blue</b> line). “Non-killer” pathogens use effectors to block host PCD as part of their infection strategy (<b>green</b> line). “Killer” pathogens thrive on this host response and use it to their advantage by activating PCD processes in the host (<b>black</b> arrow). Host organisms use a similar approach by targeting the fungal PCD (<b>purple</b> arrow).</p

Similar symptoms caused by fungal pathogens on plants and humans.

<p>(A) Cercospora shot hole (plants), (B) dermatophytosis (ringworm) (human), (C) Botrytis rot (plant), (D) mucormycosis (human).</p

Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen -0

Min); (c) germ tube formation (90–120 min); (d,e) germ tube elongation and second nuclear division (150–180 min); (f) appressorium formation and third nuclear division (4–6 h, arrow points to the septum between the germ tube and appressorium); (g, h) formation of the second germ tube and appressorium (7–9 h). Pictures represent sequence events and are projections of optical sections. The scale bar is 5 μm.<p><b>Copyright information:</b></p><p>Taken from "Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen "</p><p>http://www.biomedcentral.com/1741-7007/6/9</p><p>BMC Biology 2008;6():9-9.</p><p>Published online 14 Feb 2008</p><p>PMCID:PMC2276476.</p><p></p

Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen -2

On). Note that the nucleus is still in the hypha out of the incipient appressorium. (b-d) Time lapse of nuclear division within the appressorium: (b) the nucleus migrates from the hypha to the appressorium neck; (c) the nucleus divides within the appressorium neck; (d) one nucleus remains inside the appressorium and the other moves back into the hypha. (B) Effect of inhibitors on appressorium formation: (a) no treatment; (b) HU (fully developed appressorium develops without nuclear division); (c) benomyl. (C) Spores of strain H1-13 were inoculated onto onion epidermis. Pictures were taken after 24 h. (a) A hypha and an appressorium develop on the surface; a primary hypha is formed inside the plant under the appressorium. Note that the primary hypha is formed before nuclear division (arrow). (b, c) Nuclear division occurs in the appressorium after primary hypha formation. A single nucleus remains inside the appressorium: (b) projections of optical sections; (c) side view of the same sample. (d) A picture showing the spore from which infection originated, a hypha that developed on the leaf, an appressorium, and the underlying developing primary hyphae with several nuclei (arrow). Note that the spore and appressorium, which are on top of the onion epidermis, contain intact nuclei. Picture is a projection of optical sections. The scale bar is 5 μm.<p><b>Copyright information:</b></p><p>Taken from "Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen "</p><p>http://www.biomedcentral.com/1741-7007/6/9</p><p>BMC Biology 2008;6():9-9.</p><p>Published online 14 Feb 2008</p><p>PMCID:PMC2276476.</p><p></p

Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen -5

Nomyl; (g, h) LatA. The scale bar is 5 μm.<p><b>Copyright information:</b></p><p>Taken from "Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen "</p><p>http://www.biomedcentral.com/1741-7007/6/9</p><p>BMC Biology 2008;6():9-9.</p><p>Published online 14 Feb 2008</p><p>PMCID:PMC2276476.</p><p></p

Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen -3

Developed on the surface of the onion epidermis contain intact nuclei. (b) After 48 h post inoculation the mycelium and appressoria on the leaf surface still retain intact nuclei. Pictures represent the scan of the surface without optical sections. (c, d) Projection of optical sections showing the hyphae on and inside the leaf 72 h post inoculation: (c) top view; (d) side view of the same image. Upper nuclei line is on the leaf surface. (B) Spores were germinated on a slide with PE. (a) Untreated hyphae of strain H1-13 showing intact nuclei. (b) Spores and hyphae of wild-type strain stained with FDA (positive staining indicates viable cells). (c) Spores of strain H1-13 were germinated and then treated with lovastatin, which induces apoptosis. Picture was taken 24 h after treatment. Note the abnormal development of the hyphae and smearing of the GFP signal, which indicates nuclei disintegration. (d) Spores of the wild-type strain were germinated and then treated with lovastatin. The sample was stained with FDA 24 h after lovastatin application. (C) TUNEL assay of mycelium on the onion epidermis. Spores of the wild-type strain were inoculated onto the onion epidermis. TUNEL staining was performed 48 h post infection. (a) DNAse-treated sample (positive control). (b) Control of a sample that was incubated only with labeling solution without the terminal transferase (negative control). (c) Picture showing a spore (black arrow), a mature appressorium and underlying primary hyphae (white arrow) stained with TUNEL. Lack of staining indicates lack of PCD (viable cells). The scale bar for (b-d) in (A) is 20 μm; for all others it is 5 μm.<p><b>Copyright information:</b></p><p>Taken from "Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen "</p><p>http://www.biomedcentral.com/1741-7007/6/9</p><p>BMC Biology 2008;6():9-9.</p><p>Published online 14 Feb 2008</p><p>PMCID:PMC2276476.</p><p></p

Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen -1

Nomyl; (g, h) LatA. The scale bar is 5 μm.<p><b>Copyright information:</b></p><p>Taken from "Cell cycle and cell death are not necessary for appressorium formation and plant infection in the fungal plant pathogen "</p><p>http://www.biomedcentral.com/1741-7007/6/9</p><p>BMC Biology 2008;6():9-9.</p><p>Published online 14 Feb 2008</p><p>PMCID:PMC2276476.</p><p></p

Genomic Analysis of the Necrotrophic Fungal Pathogens <i>Sclerotinia sclerotiorum</i> and <i>Botrytis cinerea</i>

<div><p><i>Sclerotinia sclerotiorum</i> and <i>Botrytis cinerea</i> are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of <i>S. sclerotiorum</i> and two strains of <i>B. cinerea</i>. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38–39 Mb genomes include 11,860–14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the <i>S. sclerotiorum</i> assembly to 16 chromosomes and found large-scale co-linearity with the <i>B. cinerea</i> genomes. Seven percent of the <i>S. sclerotiorum</i> genome comprises transposable elements compared to <1% of <i>B. cinerea</i>. The arsenal of genes associated with necrotrophic processes is similar between the species, including genes involved in plant cell wall degradation and oxalic acid production. Analysis of secondary metabolism gene clusters revealed an expansion in number and diversity of <i>B. cinerea</i>–specific secondary metabolites relative to <i>S. sclerotiorum</i>. The potential diversity in secondary metabolism might be involved in adaptation to specific ecological niches. Comparative genome analysis revealed the basis of differing sexual mating compatibility systems between <i>S. sclerotiorum</i> and <i>B. cinerea</i>. The organization of the mating-type loci differs, and their structures provide evidence for the evolution of heterothallism from homothallism. These data shed light on the evolutionary and mechanistic bases of the genetically complex traits of necrotrophic pathogenicity and sexual mating. This resource should facilitate the functional studies designed to better understand what makes these fungi such successful and persistent pathogens of agronomic crops.</p></div