Two-Celled Promycelia and Mating-Type Segregation in Ustilago violacea (Microbotryum violaceum)

SUMMARYThe first part of the paper provides strong supportive evidence for the previous findings (Cummins & Day, 1973; Day & Cummins, 1973) that the two alleles of the mating-type locus of the basidiomycete Ustilago violacea have different periods of inducibility during a cell cycle, and that the cell cycle characteristics of each allele are maintained in freshly isolated diploids. This difference in temporal properties of the alleles appears to be the basis of the dominance of allele a2 as it is inducible during a phase of the cell cycle when allele a1 is non-inducible. During G1 both alleles appear to be inducible and apparently ‘neutralize’ each other so that the cell cannot mate.The second part of the paper provides evidence for a unique genetic control mechanism. The evidence suggests that the period of cell cycle inducibility of a locus governing a morphogenetic pathway may be regulated by a separate control gene the cc locus, with two known alleles ccstr(a stringent or restricted period of inducibility) and ccrel (a relaxed or non-restricted period of inducibility). This hypothesis stems from analysis of a diploid that was a1· ccstr/a2· ccrel and showed dominance of allele a2 during the S and G2 phases when freshly isolated, but which became incapable of mating after a period of subculturing. Analysis of haploids derived from this diploid strain showed that both mating-type alleles were functional but that it was now homozygous for ccstr, i.e. of genotype a1· ccstr/a2·ccstr· Thus the temporal and functional aspects of the mating type alleles are determined by different loci. It is postulated that cell cycle control loci may be widespread and serve to regulate the action of genes concerned with morphogenesis in relation to other cell cycle events.

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Host adaptation in the anther smut fungus Ustilago violacea (Microbotryum violaceum): infection success, spore production and alteration of floral traits on two host species and their F1-hybrid

Oecologia ◽

10.1007/bf00328447 ◽

1996 ◽

Vol 107 (3) ◽

pp. 307-320 ◽

Cited By ~ 44

Author(s):

Arjen Biere ◽

Sonja Honders

Keyword(s):

Host Species ◽

Host Adaptation ◽

Spore Production ◽

Smut Fungus ◽

Floral Traits ◽

Microbotryum Violaceum ◽

F1 Hybrid ◽

Ustilago Violacea ◽

Anther Smut

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Sex-Specific Costs of Resistance to the Fungal Pathogen Ustilago violacea (Microbotryum violaceum) in Silene alba

Evolution ◽

10.2307/2410650 ◽

1996 ◽

Vol 50 (3) ◽

pp. 1098 ◽

Cited By ~ 46

Author(s):

Arjen Biere ◽

Janis Antonovics

Keyword(s):

Fungal Pathogen ◽

Microbotryum Violaceum ◽

Ustilago Violacea ◽

Silene Alba

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Conjugation in Ustilago violacea. I. Morphology

Canadian Journal of Microbiology ◽

10.1139/m74-029 ◽

1974 ◽

Vol 20 (2) ◽

pp. 187-191 ◽

Cited By ~ 20

Author(s):

N. H. Poon ◽

J. Martin ◽

A. W. Day

Keyword(s):

Cell Cycle ◽

Mating Type ◽

Electron Micrographs ◽

Cell Walls ◽

Plasma Membranes ◽

Smut Fungus ◽

Type Ii ◽

Opposite Mating Type ◽

Ustilago Violacea ◽

Anther Smut

Conjugation in the anther smut fungus, Ustilago violacea, is described and five stages are characterized viz. (i) intimate pairing of cells of opposite mating type; (ii) development of bumps from each cell at the point of pairing. The cell walls of opposing pegs are fused, but the plasma membranes are not yet affected; (iii) elongation of the bumps into pegs; (iv) dissolution of the walls and plasma membranes of opposing pegs at the point of contact, and the formation of a tube; (v) elongation of the tube to the mature mating configuration (about 5 μm). Electron micrographs and Nomarski interference contrast micrographs of this sequence are illustrated. The assembly of the conjugation tube begins as early as 1.5 h after the cells are mixed on mating medium and is completed in about 45 min. Even in asynchronous populations there is a burst of synchronous mating, followed by later asynchronous mating. Observations on the ability to mate of unbudded and budded cells support the evidence from cell cycle work that allele a1 mates only in the G1 phase (unbudded) while allele a2 is competent to mate during all phases.

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Intratetrad mating, heterozygosity, and the maintenance of deleterious alleles in Microbotryum violaceum (=Ustilago violacea)

Heredity ◽

10.1046/j.1365-2540.2000.00748.x ◽

2000 ◽

Vol 85 (3) ◽

pp. 231-241 ◽

Cited By ~ 74

Author(s):

Michael E Hood ◽

Janis Antonovics

Keyword(s):

Microbotryum Violaceum ◽

Ustilago Violacea ◽

Deleterious Alleles

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Dimorphic Mating-Type Chromosomes in the Fungus Microbotryum violaceum

Genetics ◽

10.1093/genetics/160.2.457 ◽

2002 ◽

Vol 160 (2) ◽

pp. 457-461 ◽

Cited By ~ 1

Author(s):

Michael E Hood

Keyword(s):

Mating Type ◽

Sex Chromosomes ◽

Dna Sequences ◽

Karyotype Analysis ◽

Sequence Similarity ◽

Large Degree ◽

Microbotryum Violaceum ◽

Mating Compatibility ◽

Electrophoretic Techniques

Abstract Fungi often mate as haploids, and sex chromosomes (i.e., mating-type chromosomes) that are dimorphic for their size or overall DNA content have never been reported in this kingdom. Using electrophoretic techniques for karyotype analysis, a highly dimorphic chromosome pair that determines mating compatibility is shown to occur in populations of the fungus Microbotryum violaceum. This substantiates the evolution of such dimorphism as a general feature associated with haploid determination of mating compatibility, which previously had been known only in haplodioecious plants (mosses and liverworts). Size-dimorphic sex chromosomes are present in a lineage of M. violaceum native to Europe, as well as a lineage native to North America. However, they are very different in size between these lineages, indicating either independent evolution of the dimorphism or a large degree of divergence since their isolation. Several DNA sequences that show sequence similarity to transposons were isolated from these sex chromosomes.

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