Fungal fimbriae. II. Their role in conjugation in Ustilago violacea

1975 ◽  
Vol 21 (4) ◽  
pp. 547-557 ◽  
Author(s):  
A. W. Day ◽  
N. H. Poon
Keyword(s):  
Cell Surface ◽  
Mating Type ◽  
Electron Micrographs ◽  
Essential Role ◽  
Smut Fungus ◽  
Mating Types ◽  
Opposite Mating Type ◽  
Sensitive Material ◽  
Ustilago Violacea ◽  
Anther Smut

During conjugation in the anther smut fungus Ustilago violacea cells of opposite mating type first pair tightly and then develop a conjugation tube or bridge between them. The cells of both mating types are covered in long fine hairs or fimbriae, some of which appear to end in knobs. Experiments involving enzyme treatments of the cell surface indicate that these fimbriae do not play an essential role in cell pairing, instead pairing seems to be initiated when one or both mating types produce amorphous masses of α-amylase-sensitive material. Electron micrographs, enzyme and inhibitor studies, and experiments using restrictive temperatures suggest, however, that fimbriae may be essential for the later stages of conjugation i.e. development of the conjugation tube. If so, it is suggested that they may permit the exchange of macromolecules between the conjugating cells, initiating localized wall-softening and wall-breakdown.

Conjugation in Ustilago violacea. I. Morphology

1974 ◽  
Vol 20 (2) ◽  
pp. 187-191 ◽  
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.

scholarly journals Transcription and Translation of the Sex Message in the Smut Fungus, Ustilago Violacea

1974 ◽  
Vol 14 (3) ◽  
pp. 451-460
Author(s):  
A. W. DAY ◽  
J. E. CUMMINS
Keyword(s):  
Messenger Rna ◽  
Mating Types ◽  
Low Doses ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Rna Molecules ◽  
Ustilago Violacea ◽  
Anther Smut ◽  
Free Media ◽  
Type Strains

Cells of opposite mating type, a1 and a2, of the anther smut, Ustilago violacea assemble a conjugation tube after about 3-4 h of mating on nutrient-free media. Low doses of ultraviolet light (u.v.) delay but do not prevent conjugation in wild-type strains if given in the first 2-3 h of mating. However, irradiation later than this period has little effect and conjugation proceeds normally. The u.v. effect is photoreactivable and we conclude that u.v. induces dimers which affect transcription of specific messenger RNA molecules needed for conjugation (‘sex message’). Our evidence suggests that the dimers may cause mistranscription rather than the complete prevention of transcription. The effect of u.v. on conjugation in reciprocal crosses of u.v.-sensitive and wild-type strains indicates clearly that both partners must complete transcription of sex messages in order to conjugate. Inactivation of either partner before transcription prevents conjugation, but conjugation proceeds when either cell is inactivated after transcription of the sex messages has occurred. These results suggest that a mutual and reciprocal exchange of information between the 2 mating-types occurs prior to the assembly of the conjugation tube.

scholarly journals Sexual conjugation in yeast. Cell surface changes in response to the action of mating hormones.

1979 ◽  
Vol 80 (2) ◽  
pp. 326-333 ◽  
Author(s):  
J S Tkacz ◽  
V L MacKay
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Surface ◽  
Mating Type ◽  
Mating Types ◽  
Opposite Mating Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Yeast Cell Surface ◽  
Cell Surface Changes ◽  
Surface Changes ◽  
In Cells

In the yeast Saccharomyces cerevisiae, sexual conjugation between haploid cells of opposite mating type results in the formation of a diploid zygote. When treated with fluorescently labeled concanavalin A, a zygote stains nonuniformly, with the greatest fluorescence occurring at the conjugation bridge between the two haploid parents. In the mating mixture, unconjugated haploid cells often elongate to pear-shaped forms ("shmoos") which likewise exhibit asymmetric staining with the most intense fluorescence at the growing end. Shmoo formation can be induced in cells of one mating type by the addition of a hormone secreted by cells of the opposite mating type; such shmoos also stain asymmetrically. In nearly all cases, the nonmating mutants that were examined stained uniformly after incubation with the appropriate hormone. Asymmetric staining is not observed with vegetative cells, even those that are budded. These results suggest that, before and during conjugation, localized cell surface changes occur in cells of both mating types; the surface alterations facilitate fusion and are apparently mediated by the hormones in a manner that is mating-type specific.

scholarly journals Evolutionary strata on young mating-type chromosomes despite the lack of sexual antagonism

2017 ◽  
Vol 114 (27) ◽  
pp. 7067-7072 ◽  
Author(s):  
Sara Branco ◽  
Hélène Badouin ◽  
Ricardo C. Rodríguez de la Vega ◽  
Jérôme Gouzy ◽  
Fantin Carpentier ◽  
...  
Keyword(s):  
Mating Type ◽  
Balancing Selection ◽  
Smut Fungi ◽  
Mating Types ◽  
Sexual Antagonism ◽  
Recombination Suppression ◽  
Ancestral Gene ◽  
Anther Smut ◽  
Mating Type Genes ◽  
Suppressed Recombination

Sex chromosomes can display successive steps of recombination suppression known as “evolutionary strata,” which are thought to result from the successive linkage of sexually antagonistic genes to sex-determining genes. However, there is little evidence to support this explanation. Here we investigate whether evolutionary strata can evolve without sexual antagonism using fungi that display suppressed recombination extending beyond loci determining mating compatibility despite lack of male/female roles associated with their mating types. By comparing full-length chromosome assemblies from five anther-smut fungi with or without recombination suppression in their mating-type chromosomes, we inferred the ancestral gene order and derived chromosomal arrangements in this group. This approach shed light on the chromosomal fusion underlying the linkage of mating-type loci in fungi and provided evidence for multiple clearly resolved evolutionary strata over a range of ages (0.9–2.1 million years) in mating-type chromosomes. Several evolutionary strata did not include genes involved in mating-type determination. The existence of strata devoid of mating-type genes, despite the lack of sexual antagonism, calls for a unified theory of sex-related chromosome evolution, incorporating, for example, the influence of partially linked deleterious mutations and the maintenance of neutral rearrangement polymorphism due to balancing selection on sexes and mating types.

scholarly journals Extensive Divergence Between Mating-Type Chromosomes of the Anther-Smut Fungus

Genetics ◽  
2012 ◽  
Vol 193 (1) ◽  
pp. 309-315 ◽  
Author(s):  
Michael E. Hood ◽  
Elsa Petit ◽  
Tatiana Giraud
Keyword(s):  
Mating Type ◽  
Smut Fungus ◽  
Anther Smut

Fimbrial-dependent mating inMicrobotryum violaceuminvolves a mannose–lectin interaction

1996 ◽  
Vol 42 (5) ◽  
pp. 461-466 ◽  
Author(s):  
Alan J. Castle ◽  
Nadia Stocco ◽  
Robert Boulianne
Keyword(s):  
Cell Adhesion ◽  
Concanavalin A ◽  
Smut Fungus ◽  
Mating Types ◽  
Carbohydrate Component ◽  
Microbotryum Violaceum ◽  
Anther Smut ◽  
Cell To Cell Adhesion ◽  
Fimbrial Protein ◽  
Dependent Mechanism

Fimbriae of the anther smut fungus, Microbotryum violaceum are polymers of six 74-kDa glycoprotein isoforms. Digestion of fimbrial monomers with α-mannosidase yielded two polypeptides with masses of 70 and 48 kDa. The 70-kDa polypeptide is probably a product of incomplete digestion and the 48-kDa polypeptide is the aglycone. Thus, most of the carbohydrate component of fimbrial protein is mannose. Previous observations have suggested that fimbriae are necessary for mating in M. violaceum. Further evidence for this role was obtained in the present study by showing that mating is inhibited by an anti-fimbrial protein antiserum, by mannose and related sugars glucose and arabinose, and by the lectin concanavalin A. Since inhibition was not complete, however, two mechanisms for adhesion between compatible cells were proposed, one fimbrial dependent and one independent. Lastly, fimbrial protein from a1but not a2mating types bound to a mannose–agarose column, suggesting a lectin-like capability. The fimbrial dependent mechanism of cell-to-cell adhesion may involve binding of the mannose residues of the fimbriae of a2cells by the fimbriae of a1cells.Key words: mating, Microbotryum violaceum, lectin, fimbriae.

A SUPPRESSOR OF THE HETEROKARYON- INCOMPATIBILITY ASSOCIATED WITH MATING TYPE IN NEUROSPORA CRASSA

1970 ◽  
Vol 12 (4) ◽  
pp. 914-926 ◽  
Author(s):  
Dorothy Newmeyer
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Vegetative Growth ◽  
Mode Of Action ◽  
Wild Strain ◽  
Group Iv ◽  
Mating Types ◽  
Vegetative Incompatibility ◽  
Opposite Mating Type

Neurospora crassa strains of opposite mating type are ordinarily heterokaryon-incompatible during vegetative growth. An unlinked mutant called tolerant (tol) is described, which suppresses the vegetative incompatibility of unlike mating types without affecting their ability to cross. The mutant tol was selected and studied by means of duplications heterozygous for mating type. Use of the duplication eliminates complications due to unlinked heterokaryon genes. The mode of action of tol has been confirmed by conventional heterokaryon tests. tol has been mapped in linkage group IV, close to tryp-4. A suppressor similar or identical to tolerant has been found in a wild strain from Panama, out of 14 different wild types which were tested. By using a different duplication which covers the unlinked heterokaryon-compatibility locus C, it was shown that tolerant does not suppress C/c incompatibility. The fact that tolerant suppresses only one of the two functions ascribed to mating type revives the question of whether 'mating-type' is one gene or two. However, the data strongly support Pittenger's (1957) conclusion that, if two genes are involved, they must be closely linked.

scholarly journals Differential gene expression is associated with degeneration of mating-type chromosomes in the absence of sexual antagonism

2019 ◽  
Author(s):  
Wen-Juan Ma ◽  
Fantin Carpentier ◽  
Tatiana Giraud ◽  
Michael Hood
Keyword(s):  
Gene Expression ◽  
Differential Expression ◽  
Differential Gene Expression ◽  
Mating Type ◽  
Mating Types ◽  
Antagonistic Selection ◽  
Expression Of Genes ◽  
Sexually Antagonistic Selection ◽  
Differential Gene ◽  
Anther Smut

AbstractIn animals and plants, differential expression of genes on sex chromosomes is widespread and it is usually considered to result from sexually antagonistic selection; however differential expression can also be caused by asymmetrical sequence degeneration in non-recombining sex chromosomes, which has been very little studied. The anther-smut fungus Microbotryum lychnidis-dioicae is ideal to investigate the extent to which differential gene expression is associated with sequence degeneration because: 1) separate haploid cultures of opposite mating types help identify differential expression, 2) its mating-type chromosomes display multiple evolutionary strata reflecting successive events of gene linkage to the mating-type loci, and 3) antagonistic selection is unlikely between isogamous haploid mating types. We therefore tested the hypothesis that differential gene expression between mating types resulted from sequence degeneration. We found that genes showing differential expression between haploid mating types were enriched only on the oldest evolutionary strata of the mating-type chromosomes and were associated with multiple signatures of sequence degeneration. We found that differential expression between mating types was associated with elevated differences between alleles in non-synonymous substitution rates, indels and premature stop codons, transposable element insertions, and altered intron and GC content. Our findings strongly suggest that degenerative mutations are important in the evolution of differential expression in non-recombining regions. Our results are relevant for a broad range of taxa where mating compatibility or sex is determined by genes located in large regions of recombination suppression, showing that differential expression should not be taken as necessarily arising from antagonistic selection.Author SummaryDifferences between males and females, from morphology to behavior and physiology, are considered to largely reflect differential expression of genes that maximize fitness benefits relative to costs that are specific to one sex. However, there is an unexplored alternative to such ‘sexually antagonistic selection’ to explain differential expression. Reproductive compatibility is often determined by genes located in large non-recombining chromosomal regions, where degenerative mutations are expected to accumulate and may separately affect the expression of alternate alleles of genes. We tested the role of genetic degeneration in determining differential expression between the isogamous haploid mating types of the anther-smut fungus, Microbotryum lychnidis-dioicae, where sexually antagonistic selection is not a confounding factor. We show that differentially expressed genes are highly enriched in the non-recombining mating-type chromosomes, and that they are associated with various forms of degenerative mutations, some of which indicate that the less expressed allele suffers greater mutational effects. Our finding of the role for degenerative mutations in the evolution of differential expression is relevant for a broad range of organisms where reproductive compatibility or sex is determined by genes in regions of suppressed recombination, and shows that differential expression should not be taken as necessarily arising from antagonistic selection.

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