Genetic mapping and non-Mendelian segregation of mating type loci in the oomycete, Phytophthora infestans.

Genetics ◽  
1995 ◽  
Vol 141 (2) ◽  
pp. 503-512 ◽  
Author(s):  
H S Judelson ◽  
L J Spielman ◽  
R C Shattock
Keyword(s):  
Phytophthora Infestans ◽  
Mating Type ◽  
Dna Markers ◽  
Bulked Segregant Analysis ◽  
Random Amplified Polymorphic Dna ◽  
Mating Types ◽  
Mendelian Segregation ◽  
Range Restriction ◽  
Type Locus ◽  
Mating Type Locus

Abstract DNA markers linked to the determinants of mating type in the oomycete, Phytophthora infestans, were identified and used to address the genetic basis of heterothallism in the normally diploid fungus. Thirteen loci linked to the A1 and A2 mating types were initially identified by bulked segregant analysis using random amplified polymorphic DNA markers (RAPDs) and subsequently scored in three crosses polymorphisms (SSCP), cleaved amplified polymorphisms (CAPS), or allele-specific polymerase chain reaction markers (AS-PCR). All DNA markers mapped to a single region, consistent with a single locus determining both mating types. Long-range restriction mapping also demonstrated the linkage of the markers to one region and delimited the mating type locus to a 100-kb region. The interval containing the mating type locus displayed non-Mendelian segregation as only two of the four expected genotypes were detected in progeny. This is consistent with a system of balance lethal loci near the mating type locus. A model for mating type determination is presented in which the balanced lethals exclude form progeny those with potentially conflicting combinations of mating type alleles, such as those simultaneously expressing A1 and A2 functions.

scholarly journals Genetic and Physical Variability at the Mating Type Locus of the Oomycete, Phytophthora infestans

Genetics ◽  
1996 ◽  
Vol 144 (3) ◽  
pp. 1005-1013 ◽  
Author(s):  
Howard S Judelson
Keyword(s):  
Phytophthora Infestans ◽  
Dna Fingerprinting ◽  
Mating Type ◽  
Chromosomal Region ◽  
Single Locus ◽  
Mendelian Segregation ◽  
Genetic Analyses ◽  
Type Locus ◽  
Mating Type Locus ◽  
Type Data

Abstract Mating type in the oomyceteous fungus, Phytophthora infestans, is determined by a single locus. In a previous study of a few isolates, the locus segregated in a manner genetically consistent with its linkage to a system of balanced lethal loci. To determine the prevalence of this phenomenon within P. infestans, genetic analyses were performed using isolates representative of the diversity within the species that had been selected by DNA fingerprinting using probes linked to mating type. Non-Mendelian segregation of the mating type locus was observed in crosses performed with each isolate. An unusual group of isolates was identified in which the mating type determinants had been rearranged within the genome; these strains also produced an aberrantly large number of self-fertile progeny. Curiously, in all isolates, markers linked to the mating type locus appeared prone to duplication, transposition, deletion, or other rearrangement. This was not observed for loci unlinked to mating type. Data from the crosses and analyses of marker variation were used to erect models to explain the bases of mating type determination and of the unusual segregation of the chromosomal region containing the mating type locus.

INTERCONVERSION OF YEAST MATING TYPES II. RESTORATION OF MATING ABILITY TO STERILE MUTANTS IN HOMOTHALLIC AND HETEROTHALLIC STRAINS

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 373A-393
Author(s):  
James B Hicks ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Yeast Cells ◽  
Mating Types ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Ability ◽  
Mating Type Locus ◽  
Regulatory Information ◽  
Ho Gene

ABSTRACT The two mating types of the yeast Saccharomyces cerevisiae can be interconverted in both homothallic and heterothallic strains. Previous work indicates that all yeast cells contain the information to be both a and α and that the HO gene (in homothallic strains) promotes a change in mating type by causing a change at the mating type locus itself. In both heterothallic and homothallic strains, a defective α mating type locus can be converted to a functional a locus and subsequently to a functional α locus. In contrast, action of the HO gene does not restore mating ability to a strain defective in another gene for mating which is not at the mating type locus. These observations indicate that a yeast cell contains an additional copy (or copies) of α information, and lead to the "cassette" model for mating type interconversion. In this model, HM  a and hmα loci are blocs of unexpressed α regulatory information, and HMα and hm  a loci are blocs of unexpressed a regulatory information. These blocs are silent because they lack an essential site for expression, and become active upon insertion of this information (or a copy of the information) into the mating type locus by action of the HO gene.

scholarly journals A SUPPRESSOR OF MATING-TYPE LOCUS MUTATIONS IN SACCHAROMYCES CEREVISIAE: EVIDENCE FOR AND IDENTIFICATION OF CRYPTIC MATING-TYPE LOCI

Genetics ◽  
1979 ◽  
Vol 93 (4) ◽  
pp. 877-901 ◽  
Author(s):  
Jasper Rine ◽  
Jeffrey N Strathern ◽  
James B Hicks ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Mating Types ◽  
Type Locus ◽  
Mating Ability ◽  
Mating Type Locus ◽  
A Cells

ABSTRACT A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S. cereuisiae. This suppressor, sir1-1, restores mating ability to matαl and matα2 mutants and restores sporulation ability to matα2 and mata1 mutants. MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to α-factor, both properties of a/α diploids. Furthermore, sir1-1 allows MATa/MATa, matα1/matα1, and MATα/MATα strains to sporulate efficiently. All actions of sir1-1 are recessive to SIR1. The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed. The ability of sir1-1 to suppress the matαl-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to α. Thus, as predicted by the cassette model, HMa is functionally equivalent to MATα since it supplies functions of MATα. We propose that sir1-1 is defective in a function, Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HMα.

scholarly journals Genetic Analysis of Metalaxyl Insensitivity Loci in Phytophthora infestans Using Linked DNA Markers

1997 ◽  
Vol 87 (10) ◽  
pp. 1034-1040 ◽  
Author(s):  
Anna-Liisa Fabritius ◽  
Richard C. Shattock ◽  
Howard S. Judelson
Keyword(s):  
Phytophthora Infestans ◽  
Dna Markers ◽  
Bulked Segregant Analysis ◽  
Random Amplified Polymorphic Dna ◽  
Polymorphism Analysis ◽  
Minor Effect ◽  
Chromosomal Locus ◽  
The United Kingdom ◽  
Different Strains ◽  
Late Blight Pathogen

Previous studies indicated that incompletely dominant loci determine insensitivity by oomycetes to phenylamide fungicides such as metalaxyl. To compare the bases of insensitivity in different strains of the late blight pathogen, Phytophthora infestans, crosses were performed between sensitive isolates and isolates from Mexico, the Netherlands, and the United Kingdom that displayed varying levels of insensitivity. Segregation analyses indicated that metalaxyl insensitivity was determined primarily by one locus in each isolate, and that two of the isolates were heterozygous and the other homozygous for the insensitive allele. Metalaxyl insensitivity was also affected by the segregation of additional loci of minor effect. DNA markers linked to insensitivity were obtained by bulked segregant analysis using random amplified polymorphic DNA (RAPD) markers and the Dutch and Mexican crosses. By studying the linkage relationships between these markers and the insensitivity in each cross by RAPD or restriction fragment length polymorphism analysis, it appeared that the same chromosomal locus conferred insensitivity in the Mexican and Dutch isolates. However, a gene at a different chromosomal position was responsible for insensitivity in the British isolate.

scholarly journals Identification of the first oomycete mating-type locus sequence in the grapevine downy mildew pathogen, Plasmopara viticola

2020 ◽  
Author(s):  
Yann Dussert ◽  
Ludovic Legrand ◽  
Isabelle D. Mazet ◽  
Carole Couture ◽  
Marie-Christine Piron ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Mating Type ◽  
Type Systems ◽  
Plasmopara Viticola ◽  
Plant Diseases ◽  
Mating Types ◽  
Type Locus ◽  
Grapevine Downy Mildew ◽  
Mating Type Locus ◽  
A Genome

ABSTRACTMating types are self-incompatibility systems that promote outcrossing in plants, fungi and oomycetes. Mating-type genes have been widely studied in plants and fungi, but have yet to be identified in oomycetes, eukaryotic organisms closely related to brown algae that cause many destructive animal and plant diseases. We identified the mating-type locus of Plasmopara viticola, the oomycete responsible for grapevine downy mildew, one of the most damaging grapevine diseases worldwide. Using a genome-wide association approach, we identified a 570 kb repeat-rich non-recombining region controlling mating types, with two highly divergent alleles. We showed that one mating type was homozygous, whereas the other was heterozygous at this locus. The mating-type locus encompassed 40 genes, including one encoding a putative hormone receptor. Our findings have fundamental implications for our understanding of the evolution of mating types, as they reveal a unique determinism involving an asymmetry of heterozygosity, as in sex chromosomes and unlike other mating-type systems. This identification of the mating-type locus in such an economically important crop pathogen also has applied implications, as outcrossing facilitates rapid evolution and resistance to harsh environmental conditions.

scholarly journals INTERCONVERSION OF YEAST MATING TYPES III. ACTION OF THE HOMOTHALLISM (HO) GENE IN CELLS HOMOZYGOUS FOR THE MATING TYPE LOCUS

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 395-405 ◽  
Author(s):  
James B Hicks ◽  
Jeffrey N Strathern ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Life Cycle ◽  
Gene Product ◽  
Direct Observation ◽  
Mating Type ◽  
Mating Types ◽  
Type Locus ◽  
Mating Type Locus ◽  
Mating Type Switching ◽  
Ho Gene

ABSTRACT Mating type interconversion in homothallic Saccharomyces cerevisiae has been studied in diploids homozygous for the mating type locus produced by sporulation of a/a/a/α and a/a/α/α tetraploid strains. Mating type switches have been analyzed by techniques including direct observation of cells for changes in α-factor sensitivity. Another method of following mating type switching exploits the observation that a/α cells exhibit polar budding and a/a and α/α cells exhibit medial budding.—These studies indicate the following: (1) The allele conferring the homothallic life cycle (HO) is dominant to the allele conferring the heterothallic life cycle (ho). (2) The action of the HO gene is controlled by the mating type locus—active in a/a and α/α cells but not in a/α cells. (3) The HO (or HO-controlled) gene product can act independently on two mating type alleles located on separate chromosomes in the same nucleus. (4) A switch in mating type is observed in pairs of cells, each of which has the same change.

scholarly journals Size variation of the non-recombining region on the mating-type chromosomes in the fungal Podospora anserina species complex

2021 ◽  
Author(s):  
Fanny E Hartmann ◽  
S Lorena Ament-Velásquez ◽  
Aaron A Vogan ◽  
Valérie Gautier ◽  
Stephanie Le Prieur ◽  
...  
Keyword(s):  
Mating Type ◽  
Sex Chromosomes ◽  
Chromosomal Rearrangements ◽  
Size Variation ◽  
Sequence Divergence ◽  
Podospora Anserina ◽  
Strong Linkage Disequilibrium ◽  
Mating Types ◽  
Type Locus ◽  
Mating Type Locus

Abstract Sex chromosomes often carry large non-recombining regions that can extend progressively over time, generating evolutionary strata of sequence divergence. However, some sex chromosomes display an incomplete suppression of recombination. Large genomic regions without recombination and evolutionary strata have also been documented around fungal mating-type loci, but have been studied in only a few fungal systems. In the model fungus Podospora anserina (Ascomycota, Sordariomycetes), the reference S strain lacks recombination across a 0.8 Mb region around the mating-type locus. The lack of recombination in this region ensures that nuclei of opposite mating types are packaged into a single ascospore (pseudo-homothallic lifecycle). We found evidence for a lack of recombination around the mating-type locus in the genomes of 10 P. anserina strains and six closely related pseudo-homothallic Podospora species. Importantly, the size of the non-recombining region differed between strains and species, as indicated by the heterozygosity levels around the mating-type locus and experimental selfing. The non-recombining region is probably labile and polymorphic, differing in size and precise location within and between species, resulting in occasional, but infrequent, recombination at a given base pair. This view is also supported by the low divergence between mating types, and the lack of strong linkage disequilibrium, chromosomal rearrangements, trans-specific polymorphism and genomic degeneration. We found a pattern suggestive of evolutionary strata in P. pseudocomata. The observed heterozygosity levels indicate low but non-null outcrossing rates in nature in these pseudo-homothallic fungi. This study adds to our understanding of mating-type chromosome evolution and its relationship to mating systems.

scholarly journals Maintaining Two Mating Types: Structure of the Mating Type Locus and Its Role in Heterokaryosis inPodospora anserina

Genetics ◽  
2014 ◽  
Vol 197 (1) ◽  
pp. 421-432 ◽  
Author(s):  
Pierre Grognet ◽  
Frédérique Bidard ◽  
Claire Kuchly ◽  
Laetitia Chan Ho Tong ◽  
Evelyne Coppin ◽  
...  
Keyword(s):  
Mating Type ◽  
Mating Types ◽  
Type Locus ◽  
Mating Type Locus
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