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  • 1
    Electronic Resource
    Electronic Resource
    Cross-talk between cAMP and calcium signalling in Aspergillus niger (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Very little is known about cross-talk between cAMP and calcium signalling in filamentous fungi. The aim of this study was to analyse the influence of cAMP and protein kinase A (PKA)-dependent phosphorylation on calcium signalling in Aspergillus niger. For this purpose, cytosolic free calcium ([Ca2+]c) was measured in living hyphae expressing codon-optimized aequorin. The calcium signature following mechanical perturbation was analysed after applying dibutryl-cAMP or IBMX which increased intracellular cAMP, or H7 which inhibited phosphorylation by PKA. Calcium signatures were also measured in mutant strains in which phosphorylation by PKA was increased or lacking. The results indicated that calcium channels were activated by cAMP-mediated, PKA-dependent phosphorylation. Further evidence for cross-talk between cAMP and calcium signalling came from the analysis of a mutant in which the catalytic subunit of PKA was under the control of an inducible promoter. The consequence of PKA induction was a transient increase in [Ca2+]c which correlated with a polar–apolar transition in hyphal morphology. A transient increase in [Ca2+]c was not observed in this mutant when the morphological shift was in the opposite direction. The [Ca2+]c signatures in response to mechanical perturbation by polarized and unpolarized cells were markedly different indicating that these two cell types possessed different calcium signalling capabilities. These results were consistent with PKA-dependent phosphorylation increasing [Ca2+]c to induce a polar to apolar shift in hyphal morphology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04541.x
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium Waves and Dynamics Visualized by Confocal Microscopy in Xenopus Oocytes Expressing Cloned TRH Receptors (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 6 (1994), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Laser scanning confocal microscopy was used to analyse changes in free cytosolic calcium ([Ca2+]i) in Xenopus laevis oocytes expressing the cloned rat TRH receptor in response to TRH. In oocytes expressing TRH receptors, TRH invariably evoked a dose-dependent, biphasic calcium response. This response consisted of an initial transient planar wave of calcium propagating just below the surface of the membrane followed by a slower, secondary calcium phase. The TRH antagonist, chlordiazepoxide, markedly inhibited this calcium wave. The origins of calcium involved in this biphasic response were investigated using a variety of intra- and extra-cellular calcium antagonists. The intracellular calcium antagonists thapsigargin and TMB-8 reduced the initial and to a lesser extent the secondary phase of the planar calcium wave. In contrast, EGTA and the calcium channel blocker nifedipine produced a profound inhibition of the secondary phase while the initial phase was only slightly reduced. These results indicate that the release of intracellular calcium is predominantly responsible for the initial phase of the calcium wave while the influx of extracellular calcium is mainly involved in the secondary phase. Qualitative changes in the patterns of calcium release induced by TRH were observed following pretreatment with intracellular calcium antagonists. Following pretreatment with these compounds, TRH induced spiral or regenerative calcium waves. Addition of EGTA to the extracellular medium did not alter these responses confirming the importance of intracellular calcium in the generation of these spiral calcium waves. This study demonstrates the nature and multiplicity of regulating mechanisms of [Ca2+]i following activation of TRH receptors expressed in Xenopus oocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1994.tb00569.x
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  • 3
    Electronic Resource
    Electronic Resource
    Conidial anastomosis tubes in filamentous fungi (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 249 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Conidial anastomosis tubes (CATs) can be recognized in 73 species of filamentous fungi covering 21 genera, and develop in culture and in host-pathogen systems. They have been shown to be morphologically and physiologically distinct from germ tubes in Colletotrichum and Neurospora, and under separate genetic control in Neurospora. CATs are short, thin, usually unbranched and arise from conidia or germ tubes. Their formation is conidium-density dependent, and CATs grow towards each other. MAP kinase mutants of Neurospora are blocked in CAT induction. Nuclei pass through fused CATs and are potential agents of gene exchange between individuals of the same and different species. CAT fusion may also serve to improve the chances of colony establishment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.06.048
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  • 4
    Electronic Resource
    Electronic Resource
    Role of external signals in regulating the pre-penetration phase of infection by the rice blast fungus,Magnaporthe grisea (1994)
    Springer
    Planta 194 (1994), S. 471-477 
    Details
    ISSN: 1432-2048
    Keywords: Appressorium ; Contact sensing ; Infection structure ; Magnaporthe ; Oryza ; Rice blast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of external signals (particularly the substratum surface and light) in regulating the pre-penetration phase ofMagnaporthe grisea (Herbert) Barr [anamorph,Pyricularia grisea Sacc.] were analysed on rice (Oryza sativa L.) leaves, artificial substrata and in liquid suspension. Surface contact was found to be essential for appressorium induction but not conidium germination. Both a high surface hydrophobicity and light favoured the formation of short differentiated germ tubes and large numbers of appressoria, but neither factor was essential for their induction. Light intensity had a graded effect on the lengths of differentiated germ tubes but not on the number of appressoria formed. Higher numbers of appressoria differentiated on rice leaves than on artificial substrata suggesting that the host provides additional factors, and thus a more conducive environment, for promoting appressorium formation. Our study indicates that the pre-penetration phase of rice blast infection involves a programme of growth and differentiation triggered at conidium germination and regulated by multiple signals from the host and environment. No evidence was found for a single, external signal which initiates appressorium formation. Starvation is suggested as providing the necessary intracellular signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714458
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  • 5
    Electronic Resource
    Electronic Resource
    The genome sequence of the filamentous fungus Neurospora crassa (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 422 (2003), S. 859-868 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Neurospora crassa is a central organism in the history of twentieth-century genetics, biochemistry and molecular biology. Here, we report a high-quality draft sequence of the N. crassa genome. The approximately 40-megabase genome encodes about 10,000 protein-coding genes—more than twice as ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01554
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  • 6
    Electronic Resource
    Electronic Resource
    The genome sequence of the rice blast fungus Magnaporthe grisea (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 434 (2005), S. 980-986 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Magnaporthe grisea is the most destructive pathogen of rice worldwide and the principal model organism for elucidating the molecular basis of fungal disease of plants. Here, we report the draft sequence of the M. grisea genome. Analysis of the gene set provides an insight into the adaptations ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03449
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  • 7
    Electronic Resource
    Electronic Resource
    Role of topography sensing for infection-structure differentiation in cereal rust fungi (1997)
    Springer
    Planta 202 (1997), S. 163-170 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Appressorium ; Cereal rusts ; Infection structure ; Puccinia ; Topography-sensing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Over 90% of the germ tubes of Puccinia graminis tritici (wheat stem rust) and Puccinia hordei (barley brown rust) differentiate appressoria on encountering stomata.There has been controversy as to the role of host topographical signals in the highly precise and efficient induction of these infection structures over stomata by cereal rusts. In the present study, polystyrene replicas of microfabricated silicon wafers, bearing precise microtopographies of defined dimensions, were used to investigate the influence of ridge spacing and height on infection-structure induction by P. graminis tritici and P. hordei. It was found that artificial topographical signals alone can induce a reproducibly high percentage (83–86%) of germ tubes to differentiate infection structures. Multiple, closely spaced (1.5 μm) ridges which were 2.0 μm high provided the most inductive topography. Differentiation on flat surfaces and over single ridges was 〈 4%. Appressorium induction commonly initiated a cascade of differentiation events involving the formation of infection pegs, vesicles, infection hyphae, and occasionally haustorial mother cells. It is suggested that the close spacing of cell junctions associated with the dumbbell-shaped guard cells of cereal stomatal complexes provide inductive signals for infection-structure formation by cereal rusts in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050115
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