Morphological and Mutational Analysis of Mating in Ustilago hordei

Martínez-Espinoza, Alfredo D.; Gerhardt, Shirley A.; Sherwood, John E.

doi:10.1006/emyc.1993.1019

Cited by 30 publications

(13 citation statements)

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“…Bioassays were performed as previously described (Martinez-Espinoza et al, 1993). For pheromone response, 1 l of sample prepared as a 1 mg/ml solution in water or methanol was placed on an agar square and allowed to absorb, and MAT-1 or MAT-2 cells were added to assay MAT-2 or MAT-1 pheromone analogs, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The two mating types, MAT-1 and MAT-2, produce pheromones that bind to the complementary receptor of their mating partner and induce the formation of conjugation tubes. Conjugation tubes of opposite mating types grow toward each other, presumably by chemotropism, and fuse, resulting in the formation of dikaryotic mycelium (Martinez-Espinoza et al, 1993). This mycelium infects the seedling and grows through the plant until seed formation, when the mycelium differentiates to form teliospores.…”

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confidence: 99%

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Structural Requirements for Activity of the Pheromones of Ustilago hordei

Kosted

Gerhardt

Anderson

et al. 2000

Fungal Genetics and Biology

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Structural Requirements for Activity of the Pheromones of Ustilago hordei

Kosted

Gerhardt

Anderson

et al. 2000

Fungal Genetics and Biology

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“…Strains used in this study are listed in Table 1. Fungal strains were grown and mating tests were performed as described (12,13).…”

Section: Methodsmentioning

confidence: 99%

“…The b locus controls pathogenicity and completion of the life cycle through self vs. nonself recognition between bE and bW polypeptides to establish a regulatory factor (8,9). The homologues of the a and b genes from U. maydis and U. hordei are conserved in structure and function (2,3,(10)(11)(12). In both species, only cells of opposite mating type, that is, having different specificities at both a and b, successfully mate and form colonies with aerial hyphae (fuz ϩ reaction); these combinations are infectious when inoculated into host plants.…”

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The mating-type and pathogenicity locus of the fungus Ustilago hordei spans a 500-kb region

Lee

Bakkeren

Wong

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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110

103

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The fungal pathogen Ustilago hordei causes the covered smut disease of barley and oats. Mating and pathogenicity in this fungus are controlled by the MAT locus, which contains two distinct gene complexes, a and b. In this study, we tagged the a and b regions with the recognition sequence for the restriction enzyme I-SceI and determined that the distance between the complexes is 500 kb in a MAT-1 strain and 430 kb in a MAT-2 strain. Characterization of the organization of the known genes within the a and b gene complexes provided evidence for nonhomology and sequence inversion between MAT-1 and MAT-2. Antibiotic-resistance markers also were used to tag the a gene complex in MAT-1 strains (phleomycin) and the b gene complex in MAT-2 strains (hygromycin). Crosses were performed with these strains and progeny resistant to both antibiotics were recovered at a very low frequency, suggesting that recombination is suppressed within the MAT region. Overall, the chromosome homologues carrying the MAT locus of U. hordei share features with primitive sex chromosomes, with the added twist that the MAT locus also controls pathogenicity.MAT locus ͉ sex chromosome ͉ smut disease ͉ phytopathogen ͉ basidiomycete U stilago hordei represents a group of fungal pathogens that cause economically important smut diseases on small-grain cereals (1). These fungi grow as hyphae within developing seedlings without causing symptoms; upon flowering of the host plant, the fungal cells proliferate and form masses of dark teliospores that replace the seeds. The diploid teliospores germinate and undergo meiosis to yield haploid cells. These meiotic progeny must mate to infect the host, and infection is a prerequisite for completion of the sexual phase of the life cycle, i.e., the formation of teliospores. Sex and pathogenicity therefore are interconnected in U. hordei and related smut fungi, and the mating-type genes are considered pathogenicity factors.U. hordei has a bipolar mating system controlled by one mating-type locus (MAT) with two alleles or alternative specificities, MAT-1 and MAT-2. DNA hybridization experiments with the well-characterized a and b mating-type genes from the related species, Ustilago maydis, revealed that U. hordei possesses similar mating-type functions located at so-called a and b gene complexes within the MAT locus (2, 3). In contrast to U. hordei, U. maydis has a tetrapolar mating system because the a and b loci are on separate chromosomes and therefore segregate independently during meiosis (3, 4). Thus, the tetrapolar and bipolar mating systems are distinguished by differences in the genomic organizations of the a and b genes (3). In U. maydis, two specificities exist for the a locus: a1 and a2 (5, 6). The a locus encodes cell-type specific pheromones (mfa) as well as the pheromone receptors (pra) that recognize pheromones from compatible mating partners. The b locus of U. maydis is multiallelic and contains two divergently transcribed genes, bE (bEast) and bW (bWest) (4, 7-9). The b locus controls pathogenicity ...

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“…23 and 24) presumably control fusion events by a mechanism similar to that of the a locus of U. maydis. In fact, sequences that cross-hybridize with the U. maydis a locus and factors that may be diffusible pheromones have been detected in U. hordei (25,26). In addition, bipolar smut fungi do have homologs of the U. maydis bE and bW genes, and the b gene complexes from U. hordei are functional when transferred to U. maydis (25,27 (12,28).…”

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Linkage of mating-type loci distinguishes bipolar from tetrapolar mating in basidiomycetous smut fungi.

Bakkeren

Kronstad²

1994

Proc. Natl. Acad. Sci. U.S.A.

147

125

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Sexual compatibility requires self vs. non-self recognition. Genetically, two compatibility or mating-type systems govern recognition In heterothallic basidiomycete fungi such as the edible and woodrotting mushrooms and the economically important rust and smut phytopathogens. A bipolar system is defined by a single genetic locus (MAT) that can have two or multiple alleles. A tetrapolar system has two loci, each with two or more specificities. We have employed two species from the genus Usuilago (smut fungi) to discover a molecular explanation for the genetic difference in mating systems. Ustilago maydis, a tetrapolar species, has two genetically unlinked loci that encode the distinct mating functions of cell fusion (a locus) and subsequent sexual development and pathogenicity (b locus). We have recently described a b locus in a bipolar species, Ustiago hordei, wherein the existence of an a locus has been suspected, but not demonstrated. We report here the doning of an allele of the a locus (al) from U. hordei and the discovery that physical linkage ofthe a and b loci in this bipolar fungus accounts for the distinct mating system. Linkage establishes a large complex MAT locus in U. hordei; this locus appears to be in a region suppressed for recombination.A hallmark of the heterothallic basidiomycete fungi is the fusion of cells of different compatibility to form a dikaryotic mycelium in which each cell contains a pair of nuclei. The interaction of two non-self nuclei within one cell triggers a program of sexual development (1-5). Among the homobasidiomycetes, which include the mushrooms such as Schizophyllum commune and Coprinus cinereus (6, 7), w65% ofthe species regulate sexual compatibility genetically via a tetrapolar (bifactorial) mating system. In these fungi, two genetic loci, each with two or more allelic specificities, control sexual development. Approximately 25% of the species have a bipolar (unifactorial) mating system in which compatibility is governed by a single genetic locus. In the bipolar species, this locus can have two or multiple alleles, the latter being common in the homobasidiomycetes and the non-parasitic heterobasidiomycetes. The remaining 10% consist of homothallic species (6,8). Among the parasitic heterobasidiomycetes, such as the phytopathogenic rust, bunt, and smut fungi, the diallelic bipolar mating system is predominant with certain exceptions (9, 10). These exceptions include a multiallelic bipolar system for the bunt fungus Tilletia controversa (11) and the occurrence of a tetrapolar mating system in several smut species including Ustilago maydis and Ustilago longissima (10, 12). To our knowledge, the molecular mechanisms underlying the genetic differences between these mating systems have heretofore been unknown.Mating and dikaryon formation are intricately connected with pathogenicity in the smut fungi, and the mating-type loci in the tetrapolar smut pathogen U. maydis have recently been isolated and characterized (10,(13)(14)(15)(16)(17)(18)(19). The a locus has two s...

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Morphological and Mutational Analysis of Mating in Ustilago hordei

Cited by 30 publications

References 0 publications

Structural Requirements for Activity of the Pheromones of Ustilago hordei

Structural Requirements for Activity of the Pheromones of Ustilago hordei

The mating-type and pathogenicity locus of the fungus Ustilago hordei spans a 500-kb region

Linkage of mating-type loci distinguishes bipolar from tetrapolar mating in basidiomycetous smut fungi.

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