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1.
Pathogenic development ofUstilago maydis, the causative agent of corn smut disease, is a multistep process. Compatible yeast-like cells fuse and this generates the infectious dikaryon which grows filamentously. Having entered the plant the dikaryon induces tumors in its host in which massive proliferation of fungal material, karyogamy and spore formation occur. In order to follow fungal development from the initial steps to the final stage we have expressed the green fluorescent protein (GFP) fromAequorea victoria as a vital marker inU. maydis and demonstrate that GFP-tagged strains can be used to study host-pathogen interactions in vivo. 相似文献
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Stacey A. Bruce Barry J. Saville R. J. Neil Emery 《Journal of Plant Growth Regulation》2011,30(1):51-63
The infection of maize (Zea mays) by the basidiomycete fungus Ustilago maydis leads to common smut of corn characterized by the production of tumors in susceptible aboveground plant tissues. LC-(ES)MS/MS
profiles of abscisic acid (ABA) and 12 different cytokinins (CKs) were determined for infected and uninfected maize tissues
over a time course following fungal exposure. Samples were taken at points corresponding to the appearance of disease symptoms.
Axenic cultures of haploid and dikaryon forms of U. maydis were also profiled. This study confirmed the capability of Ustilago maydis to synthesize CKs, ABA, and auxin (IAA). It also provided evidence for the involvement of CK and ABA in the U. maydis-maize infection process. Significant quantities of CKs and ABA were detected from axenic cultures of U. maydis as was IAA. CKs and ABA levels were elevated in leaves and stems of maize after infection; notable was the high level of
cis-zeatin 9-riboside. Variation among hormone profiles of maize tissues was observed at different time points during infection
and between infections with nonpathogenic haploid and pathogenic dikaryon strains. This suggested that CKs and ABA accumulate
and are likely metabolized in maize tissue infected with U. maydis. Because U. maydis produced these phytohormones at significant levels, it is possible that the fungal pathogen is a source of these compounds
in infected tissue. This is the first study to confirm the production of CKs and document the production of ABA by U. maydis. This study also established an involvement of these phytohormones and a possible functional role for ABA in U. maydis infection of maize. 相似文献
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Disruption of two genes for chitin synthase in the phytopathogenic fungus Ustilago maydis 总被引:4,自引:2,他引:2
The phytopathogenic fungus Ustilago maydis exhibits a dimorphic transition in which non-pathogenic, yeast-like cells mate to form a pathogenic, filamentous dikaryon. Northern analysis indicated that two chitin synthase genes, chs1 and chs2, from U. maydis are expressed at similar levels in yeast-like cells and in cells undergoing the mating reaction leading to the filamentous cell type. A mutation was constructed in each of the chitin synthase genes by targeted gene disruption. Each mutant showed a reduction in the level of trypsin-activated enzyme activity, compared with a wild-type strain, but retained the wild-type morphology, the ability to mate and the ability to form the filamentous pathogenic cell type. 相似文献
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Gunther Doehlemann Ramon Wahl Miroslav Vranes Ronald P. de Vries Jrg Kmper Regine Kahmann 《Journal of plant physiology》2008,165(1):29
The fungus Ustilago maydis is a biotrophic pathogen parasitizing on maize. The most prominent symptoms of the disease are large tumors in which fungal proliferation and spore differentiation occur. In this study, we have analyzed early and late tumor stages by confocal microscopy. We show that fungal differentiation occurs both within plant cells as well as in cavities where huge aggregates of fungal mycelium develop. U. maydis is poorly equipped with plant CWDEs and we demonstrate by array analysis that the respective genes follow distinct expression profiles at early and late stages of tumor development. For the set of three genes coding for pectinolytic enzymes, deletion mutants were generated by gene replacement. Neither single nor triple mutants were affected in pathogenic development. Based on our studies, we consider it unlikely that U. maydis feeds on carbohydrates derived from the digestion of plant cell wall material, but uses its set of plant CWDEs for softening the cell wall structure as a prerequisite for in planta growth. 相似文献
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Robin J. Horst Timo Engelsdorf Uwe Sonnewald Lars M. Voll 《Journal of plant physiology》2008,165(1):19
The Basidiomycete fungus Ustilago maydis is the common agent of corn smut and is capable of inducing gall growth on infected tissue of the C4 plant maize (Zea mays). While U. maydis is very well characterized on the genetic level, the physiological changes in the host plant in response to U. maydis infection have not been studied in detail, yet.Therefore, we examined the influence of U. maydis infection on photosynthetic performance and carbon metabolism in maize leaf galls.At all stages of development, U. maydis-induced leaf galls exhibited carbon dioxide response curves, CO2 compensation points and enzymatic activities that are characteristic of C3 photosynthesis, demonstrating that the establishment of C4 metabolism is prevented in infected tissue. Hexose contents and hexose/sucrose ratio of leaf galls remained high at 6 days post infection, while a shift in free sugar metabolism was observed in the uninfected controls at that time point. Concomitantly, transitory starch production and sucrose accumulation during the light period remained low in leaf galls. Given that U. maydis is infectious on young developing tissue, the observed changes in carbohydrate metabolism suggest that the pathogen manipulates the developing leaf tissue to arrest sink-to-source transition in favor of maintaining sink metabolism in the host cells.Furthermore, evidence is presented that carbohydrate supply during the biotrophic phase of the pathogen is assured by a fungal invertase. 相似文献
7.
14-3-3 proteins are a family of highly conserved polypeptides that function as small adaptors that facilitate a diverse array of cellular processes by binding phosphorylated target proteins. One of these processes is the regulation of the cell cycle. Here we characterized the role of Bmh1, a 14-3-3 protein, in the cell cycle regulation of the fungus Ustilago maydis. We found that this protein is essential in U. maydis and that it has roles during the G2/M transition in this organism. The function of 14-3-3 in U. maydis seems to mirror the proposed role for this protein during Schizosaccharomyces pombe cell cycle regulation. We provided evidence that in U. maydis 14-3-3 protein binds to the mitotic regulator Cdc25. Comparison of the roles of 14-3-3 during cell cycle regulation in other fungal system let us to discuss the connections between morphogenesis, cell cycle regulation and the evolutionary role of 14-3-3 proteins in fungi. 相似文献
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The tarspot complex is caused by the interaction of Phyllachora maydis and Monographella maydis. Coniothyrium phyllachorae, possibly a mycoparasite, is found in older ascostromata of P. maydis, which always appears first causing tarspot. M. maydis follows and is responsible for the damaging fisheye symptom. The fisheye symptom is always associated with a tarspot in the center of the lesion, whereas 12 to 20% of the Phyllachora ascostromata remained free of M. maydis. Inoculations of maize leaves with the Microdochium anamorph of the Monographella (usually produced in lesions) failed to produce infections. Some infections with M. maydis were, however, obtained under unusual conditions in the field. Inoculations onto tarspots in the laboratory were unsuccessful, but in field experiments inoculations with conidia of M. maydis enhanced severity of the tarspot complex. Fisheye symptoms of the complex naturally appear 2 to 7 days after the manifestation of P. maydis. This is followed a week later by the appearance of M. maydis which became predominant in the lesions and is associated with empty perithecia of P. maydis. In the early stages of the tarspots pycnidia of the anamorph of P. maydis, Linochora sp., could occasionally be observed. Ascomata of M. maydis were rare in the field. Of the 36 genetic materials of CIMMYT tested, 30 developed the fisheye symptom, 4 tarspots only and 2 remained free of symptoms 相似文献
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A rapid, inexpensive bioassay to detect Myrothecium spp.-produced macrocyclic trichothecenes was developed. Media containing Myrothecium isolates were inoculated with Chlorella vulgaris, Ustilago maydis and Trichoderma viride. Based on width of the inhibition zone, isolates could be classified as highly toxigenic, non-toxigenic and intermediate. Whereas, C. vulgaris and U. maydis showed significant differences in their response to toxigenic and non-toxigenic isolates, T. viride did not. Production of roridins and verrucarins by the toxigenic isolates (by bioassay) was confirmed by thin layer chromatography and high performance liquid chromatography. This bioassay system, combined with confirmation chemical analyses, increases our ability to detect toxigenic fungal isolates. 相似文献
11.
Beatriz Xoconostle-Cázares Charles A. Specht Phillips W. Robbins Yilun Liu Claudia León José Ruiz-Herrera 《Fungal genetics and biology : FG & B》1997,22(3):199-208
A fragment corresponding to a conserved region of a fifth gene coding for chitin synthase in the plant pathogenic fungusUstilago maydiswas amplified by means of the polymerase chain reaction (PCR). The amplified fragment was utilized as a probe for the identification of the whole gene in a genomic library of the fungus. The predicted gene product ofUmchs5has highest similarity with class IV chitin synthases encoded by theCHS3genes fromSaccharomyces cerevisiaeandCandida albicans, chs-4fromNeurospora crassa,andchsEfromAspergillus nidulans. Umchs5null mutants were constructed by substitution of most of the coding sequence with the hygromycin B resistance cassette. Mutants displayed significant reduction in growth rate, chitin content, and chitin synthase activity, specially in the mycelial form. Virulence to corn plantules was also reduced in the mutants. PCR was also used to obtain a fragment of a sixth chitin synthase,Umchs6.It is suggested that multigenic control of chitin synthesis inU. maydisoperates as a protection mechanism for fungal viability in which the loss of one activity is partially compensated by the remaining enzymes. 相似文献
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Austin R Provart NJ Sacadura NT Nugent KG Babu M Saville BJ 《Functional & integrative genomics》2004,4(4):207-218
A large-scale comparative genomic analysis of unisequence sets obtained from an Ustilago maydis EST collection was performed against publicly available EST and genomic sequence datasets from 21 species. We annotated 70% of the collection based on similarity to known sequences and recognized protein signatures. Distinct grouping of the ESTs, defined by the presence or absence of similar sequences in the species examined, allowed the identification of U. maydis sequences present only (1) in fungal species, (2) in plants but not animals, (3) in animals but not plants, or (4) in all three eukaryotic lineages assessed. We also identified 215 U. maydis genes that are found in the ascomycete but not in the basidiomycete genome sequences searched. Candidate genes were identified for further functional characterization. These include 167 basidiomycete-specific sequences, 58 fungal pathogen-specific sequences (including 37 basidiomycete pathogen-specific sequences), and 18 plant pathogen-specific sequences, as well as two sequences present only in other plant pathogen and plant species.Supplemental Excel Table 1 used for analysis and the derivation of Fig. 3 as well as supplemental Tables 2 and 3 are available at All ESTs used in this analysis have been submitted to GenBank. The accession numbers are CF638289–CF645747, CF663122–CF663127, and CD487847–CD490309 (Supplemental Table 3) 相似文献
15.
Ustilago maydis is the causative agent of common smut of corn. Early studies noted its ability to synthesize phytohormones and, more recently these growth promoting substances were confirmed as cytokinins (CKs). Cytokinins comprise a group of phytohormones commonly associated with actively dividing tissues. Lab analyses identified variation in virulence between U. maydis dikaryon and solopathogen infections of corn cob tissue. Samples from infected cob tissue were taken at sequential time points post infection and biochemical profiling was performed using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS). This hormone profiling revealed that there were altered levels of ABA and major CKs, with a marked reduction in CK glucosides, increases in methylthiol CKs and a particularly dramatic increase in cisZ CK forms, in U. maydis infected tissue. These changes were more pronounced in the more virulent dikaryon relative to the solopathogenic strain suggesting a role for cytokinins in moderating virulence during biotrophic infection. These findings highlight the fact that U. maydis does not simply mimic a fertilized seed but instead reprograms the host tissue. Results underscore the suitability of the Ustilago maydis– Zea mays model as a basis for investigating the control of phytohormone dynamics during biotrophic infection of plants. 相似文献
16.
Ustilago maydis killer toxins are small polypeptides (7–14 kDa) whichkill susceptible cells of closely related fungal species. The KP4 toxin is a single polypeptide subunit with a molecular weight of 11.1 kDa. In this work, a transgenic tobacco plant was constructed which secretes the KP4 toxin at a high level. The KP4 toxin expressed in this transgenic plant was of the same size and specificity as the authentic Ustilago KP4 toxin. The expression level was at least 500 times higher than that of the KP6 toxin expressed in plants. Transgenic crop plants producing the KP4 toxin could be rendered resistant to KP4-susceptible fungal pathogens. 相似文献
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Transgenic maize plants expressing the Totivirus antifungal protein, KP4, are highly resistant to corn smut 总被引:2,自引:0,他引:2
The corn smut fungus, Ustilago maydis, is a global pathogen responsible for extensive agricultural losses. Control of corn smut using traditional breeding has met with limited success because natural resistance to U. maydis is organ specific and involves numerous maize genes. Here, we present a transgenic approach by constitutively expressing the Totivirus antifungal protein KP4, in maize. Transgenic maize plants expressed high levels of KP4 with no apparent negative impact on plant development and displayed robust resistance to U. maydis challenges to both the stem and ear tissues in the greenhouse. More broadly, these results demonstrate that a high level of organ independent fungal resistance can be afforded by transgenic expression of this family of antifungal proteins. 相似文献
18.
In the corn smut fungus Ustilago maydis, pathogenic development is initiated when two compatible haploid cells fuse and form the infectious dikaryon. Mating is dependent on pheromone recognition by compatible cells. In this report, we set out to evaluate the relationship between the cell cycle and the pheromone response in U. maydis. To achieve this, we designed a haploid pheromone-responsive strain that is able to faithfully reproduce the native mating response in nutrient-rich medium. Addition of synthetic pheromone to the responsive strain induces the formation of mating structures, and this response is abolished by mutations in genes encoding components of the pheromone signal transduction cascade. After recognition of pheromone, U. maydis cells arrest the cell cycle in a postreplicative stage. Visualization of the nucleus and microtubule organization indicates that the arrest takes place at the G2 phase. Chemical-induced cell cycle arrest and release in the presence of pheromone further support this conclusion. 相似文献
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