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1.
Cell recognition and mating in the smut fungus Ustilago maydis have been proposed to involve specific pheromones and pheromone receptors. The respective structural genes are located in the a mating type locus that exists in the alleles a1 and a2. We demonstrate that binding of pheromone to the receptor can induce a morphological switch from yeast-like to filamentous growth in certain strains. Using this as biological assay we were able to purify both the a1 and a2 pheromone. The structure of the secreted pheromones was determined to be 13 amino acids for a1 and nine amino acids for a2. Both pheromones are post-translationally modified by farnesylation and carboxyl methyl esterification of the C-terminal cysteine. An unmodified a1 peptide exhibits dramatically reduced activity. The pheromone alone is able to induce characteristic conjugation tubes in cells of opposite mating type and confers mating competence; even cells of the same mating type undergo fusion. We discuss the role of pheromones in initiating filamentous growth and pathogenic development. 相似文献
2.
Identification of a motor protein required for filamentous growth in Ustilago maydis. 总被引:5,自引:0,他引:5
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C Lehmler G Steinberg K M Snetselaar M Schliwa R Kahmann M B?lker 《The EMBO journal》1997,16(12):3464-3473
The phytopathogenic fungus Ustilago maydis exists in two stages, the yeast-like haploid form and the filamentous dikaryon. Both pathogenicity and dimorphism are genetically controlled by two mating-type loci, with only the filamentous stage being pathogenic on corn. We have identified two genes (kin1 and kin2) encoding motor proteins of the kinesin family. Kin1 is most similar to the human CENP-E gene product, while Kin2 is most closely related to the conventional kinesin Nkin of Neurospora crassa. Deletion mutants of kin1 had no discernible phenotype; delta kin2 mutants, however, were severely affected in hyphal extension and pathogenicity. The wild-type dikaryon showed rapid tip growth, with all the cytoplasm being moved to the tip compartment. Left behind are septate cell wall tubes devoid of cytoplasm. In delta kin2 mutants, dikaryotic cells were formed after cell fusion, but these hyphal structures remained short and filled with cytoplasm. A functional green fluorescent protein (GFP)-Kin2 fusion was generated and used to determine the localization of the motor protein by fluorescence microscopy. Inspection of the hyphal tips by electron microscopy revealed a characteristic accumulation of darkly stained vesicles which was absent in mutant cells. We suggest that the motor protein Kin2 is involved in organizing this specialized growth zone at the hyphal tip, probably by affecting the vectorial transport of vesicles. 相似文献
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The pheromone response factor coordinates filamentous growth and pathogenicity in Ustilago maydis. 总被引:7,自引:3,他引:4
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In Ustilago maydis, the a and b mating type loci regulate cell fusion, filamentous growth and pathogenicity. The a locus encodes a pheromone-based cell recognition system, and the b locus specifies two homeodomain proteins. The expression of all genes in the a and b loci is induced by pheromone. We have identified a HMG protein (Prf1) that binds sequence specifically to pheromone response elements present in the a and b loci. prf1 mutants do not express the a and b genes and are sterile. The disruption of prf1 in pathogenic haploid strains results in a loss of pathogenicity. The constitutive expression of the b genes restores pathogenicity and induces filamentous growth in the absence of the pheromone signal. These results provide evidence that pheromone signalling, filamentous growth and pathogenic development are linked through Prf1. 相似文献
4.
Guanyl nucleotide exchange factor Sql2 and Ras2 regulate filamentous growth in Ustilago maydis 总被引:1,自引:0,他引:1
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The cyclic AMP (cAMP)-signaling pathway regulates cell morphology and plays a crucial role during pathogenic development of the plant-pathogenic fungus Ustilago maydis. Strains lacking components of this signaling pathway, such as the Gα-subunit Gpa3 or the adenylyl cyclase Uac1, are nonpathogenic and grow filamentously. On the other hand, strains exhibiting an activated cAMP pathway due to a dominant-active allele of gpa3 display a glossy colony phenotype and are unable to proliferate in plant tumors. Here we present the identification of sql2 as a suppressor of the glossy colony phenotype of a gpa3Q206L strain. sql2 encodes a protein with similarity to CDC25-like guanine nucleotide exchange factors, which are known to act on Ras proteins. Overexpression of sql2 leads to filamentous growth that cannot be suppressed by exogenous cAMP, suggesting that Sql2 does not act upstream of Uac1. To gain more insight in signaling processes regulated by Sql2, we isolated two genes encoding Ras proteins. Expression of dominant active alleles of ras1 and ras2 showed that Ras2 induces filamentous growth while Ras1 does not affect cell morphology but elevates pheromone gene expression. These results indicate that Ras1 and Ras2 fulfill different functions in U. maydis. Moreover, observed similarities between the filaments induced by sql2 and ras2 suggest that Sql2 is an activator of Ras2. Interestingly, sql2 deletion mutants are affected in pathogenic development but not in mating, indicating a specific function of sql2 during pathogenesis. 相似文献
5.
Gene expression during Ustilago maydis diploid filamentous growth: EST library creation and analyses
Ustilago maydis is an important model system for the plant pathogenic smut and rust fungi. Critical to the continued development of this model is establishing genomic resources. We have constructed a cDNA library from a forced diploid culture of U. maydis growing as filaments and have generated 7455 ESTs that are assembled into 3074 contiguous sequences. This represents as much as 46% of the coding capacity predicted for U. maydis. BLAST searches with a similarity cutoff of E = 10(-5), allow us to annotate 59% of the contigs based upon matches in the NCBI nr and dbEST databases. These annotated sequences provide information on mature mRNAs that will aid with gene prediction in the U. maydis genome sequence. Functional categorization and comparative analyses of the sequences provides gene identities, expression information and a solid base for future research in this model fungal pathogen. 相似文献
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Saavedra E Ramos-Casillas LE Marín-Hernández A Moreno-Sánchez R Guerra-Sánchez G 《FEMS yeast research》2008,8(8):1313-1323
The kinetic parameters of the 10 glycolytic enzymes and glycolytic fluxes were determined for the first time in Ustilago maydis. Enzyme activities in yeast grown in minimal medium and harvested in the stationary stage were twofold higher than those from yeast grown in rich medium. In contrast, in yeast harvested in the exponential stage, the enzyme activities were higher in cells grown in rich medium. Phosphofructokinase activity was the lowest in the four culture conditions analyzed, suggesting that this enzyme is a flux-controlling step in U. maydis glycolysis. The V(max) and K(m) values of hexokinase and pyruvate kinase were similar under all conditions. The results revealed that U. maydis aldolase belongs to the class II type of metalo-aldolases. 3-Phosphoglycerate mutase (PGAM) activity was 2,3-bisphosphoglycerate cofactor independent, which contrasted with the cofactor dependency predicted by the amino acid sequence alignment analysis. Pyruvate was secreted by U. maydis yeast in the presence and absence of external glucose. The glycolytic enzyme activities in the U. maydis mycelial form were similar to those found in yeast, except for one order of magnitude higher phosphofructokinase and PGAM activities, thus suggesting differences in the glycolysis regulatory mechanisms between the two cellular forms. 相似文献
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Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a budding haploid saprophyte and a filamentous dikaryotic pathogen. We are interested in identifying the genetic determinants of filamentous growth and pathogenicity in U. maydis. To do this, we have taken a forward genetic approach. Previously, we showed that haploid adenylate cyclase (uac1) mutants display a constitutively filamentous phenotype. Mutagenesis of a uac1 disruption strain allowed the isolation of a large number of budding suppressor mutants. These mutants are named ubc, for Ustilago bypass of cyclase, as they no longer require the production of cAMP to grow in the budding morphology. Complementation of one of these suppressor mutants led to the identification of ubc3, which is required for filamentous growth and encodes a MAP kinase most similar to those of the yeast pheromone response pathway. In addition to filamentous growth, the ubc3 gene is required for pheromone response and for full virulence. Mutations in the earlier identified fuz7 MAP kinase kinase also suppress the filamentous phenotype of the uac1 disruption mutant, adding evidence that both ubc3 and fuz7 are members of this same MAP kinase cascade. These results support an important interplay of the cAMP and MAP kinase signal transduction pathways in the control of morphogenesis and pathogenicity in U. maydis. 相似文献
14.
The Ustilago maydis ubc4 and ubc5 genes encode members of a MAP kinase cascade required for filamentous growth 总被引:2,自引:0,他引:2
Andrews DL Egan JD Mayorga ME Gold SE 《Molecular plant-microbe interactions : MPMI》2000,13(7):781-786
Ustilago maydis, the causal agent of corn smut disease, displays dimorphic growth in which it alternates between a budding haploid saprophyte and a filamentous dikaryotic pathogen. We are interested in identifying the genetic determinants of filamentous growth and pathogenicity in U. maydis. To do this we have taken a forward genetic approach. Earlier, we showed that haploid adenylate cyclase (uac1) mutants display a constitutively filamentous phenotype. Mutagenesis of a uac1 disruption strain allowed the isolation of a large number of budding suppressor mutants. These mutants are named ubc, for Ustilago bypass of cyclase, as they no longer require the production of cyclic AMP (cAMP) to grow in the budding morphology. Complementation of a subset of these suppressor mutants led to the identification of the ubc4 and ubc5 genes, which are required for filamentous growth and encode a MAP (mitogen-activated protein) kinase kinase kinase and a MAP kinase kinase, respectively. Evidence suggests that they are important in the pheromone response pathway and in pathogenicity. These results further support an important interplay of the cAMP and MAP kinase signal transduction pathways in the control of morphogenesis and pathogenicity in U. maydis. 相似文献
15.
Summary. Filamentous fungi are an important group of tip-growing organisms, which include numerous plant pathogens such as Magnaporthe grisea and Ustilago maydis. Despite their ecological and economical relevance, we are just beginning to unravel the importance of endocytosis in filamentous
fungi. Most evidence for endocytosis in filamentous fungi is based on the use of endocytic tracer dyes that are taken up into
the cell and delivered to the vacuole. Moreover, genomewide screening for candidate genes in Neurospora crassa and U. maydis confirmed the presence of most components of the endocytic machinery, indicating that endocytosis participates in filamentous
growth. Indeed, it was shown that in U. maydis early endosomes cluster at sites of growth, where they support morphogenesis and polar growth, most likely via endosome-based
membrane recycling. In humans, such recycling processes to the plasma membrane involve small GTPases such as Rab4. A homologue
of this protein is encoded in the genome of U. maydis but is absent from the yeast Saccharomyces cerevisiae, suggesting that Rab4-mediated recycling is important for filamentous growth. Furthermore, human Rab4 regulates traffic of
early endosomes along microtubules, and a similar microtubule-based transport is described for U. maydis. These observations suggest that Rab4-like GTPases might regulate endosome- and microtubule-based recycling during tip growth
of filamentous fungi.
Correspondence and reprints: MPI für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, 35043 Marburg, Federal Republic
of Germany. 相似文献
16.
Milorad Kojic Jeanette H. Sutherland José Pérez-Martín William K. Holloman 《Genetics》2013,195(4):1231-1240
A central feature of meiosis is the pairing and recombination of homologous chromosomes. Ustilago maydis, a biotrophic fungus that parasitizes maize, has long been utilized as an experimental system for studying recombination, but it has not been clear when in the life cycle meiotic recombination initiates. U. maydis forms dormant diploid teliospores as the end product of the infection process. Upon germination, teliospores complete meiosis to produce four haploid basidiospores. Here we asked whether the meiotic process begins when teliospores germinate or at an earlier stage in development. When teliospores homozygous for a cdc45 mutation temperature sensitive for DNA synthesis were germinated at the restrictive temperature, four nuclei became visible. This implies that teliospores have already undergone premeiotic DNA synthesis and suggests that meiotic recombination initiates at a stage of infection before teliospores mature. Determination of homologous recombination in plant tissue infected with U. maydis strains heteroallelic for the nar1 gene revealed that Nar+ recombinants were produced at a stage before teliospore maturation. Teliospores obtained from a spo11Δ cross were still able to germinate but the process was highly disturbed and the meiotic products were imbalanced in chromosomal complement. These results show that in U. maydis, homologous recombination initiates during the infection process and that meiosis can proceed even in the absence of Spo11, but with loss of genomic integrity. 相似文献
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M. A. de Waard 《Antonie van Leeuwenhoek》1976,42(3):211-216
Protoplasts of Ustilago maydis were obtained by incubating sporidia of the fungus with a combination of Helicase and a commercial Onozuka R-10 enzyme preparation of Trichoderma harzianum in the presence of 0.6 m (NH4)2 SO4 as an osmotic stabilizer. In the presence of the organic stabilizers sorbitol and sucrose, however, the release of protoplasts was inhibited. Combinations of Helicase with other lytic enzymes such as cellulase from Aspergillus niger, cellulase and hemicellulase from Rhizopus, and Driselase or Nagarse were inactive. 相似文献
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玉米黑粉菌(Ustilago maydis)可在其宿主植物玉米(Zea mays L.)地上部的所有器官诱导肿瘤发生。玉米黑粉菌成功定殖宿主并诱导形成肿瘤取决于与宿主植物多方位、多层次的相互作用以及该过程中发生的复杂的细胞和分子事件。本文综述了玉米黑粉菌与玉米互作研究的最新进展,介绍了玉米黑粉菌通过分泌效应子入侵、定殖玉米植株以及植株在分子水平上对入侵的响应;阐述了活体营养建立过程中,玉米黑粉菌与玉米通过效应子、激素、糖代谢酶和转运蛋白的差异调节,协调受感染宿主组织重新编程发育成膨大的植物肿瘤的关键因素,并对今后的研究方向进行了展望。 相似文献
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Valverde María Elena Vandemark George J. Martínez Octavio Paredes-López Octavio 《World journal of microbiology & biotechnology》2000,16(1):49-55
Thirty wild isolates belonging to five different locations in Mexico plus two laboratory strains of Ustilago maydis were characterized by restriction fragment length polymorphism (RFLP) analysis using 23 different clones as probes derived from a PstI library and two restriction enzymes. All loci analysed presented a high level of polymorphism, including one locus with thirty one different alleles. Geographical grouping of the populations was based on Nei's genetic distance and there was no correlation between genetic and geographic distances among these isolates. Our results suggest that DNA fingerprinting is a useful method for detecting genetic variation in populations of U. maydis. This work demonstrated that considerable genetic variation may be present within field populations of U. maydis. 相似文献