NEW DUPLICATION-GENERATING INVERSIONS IN NEUROSPORA

1969 ◽  
Vol 11 (3) ◽  
pp. 622-638 ◽  
Author(s):  
Barbara C. Turner ◽  
Cecile W. Taylor ◽  
David D. Perkins ◽  
Dorothy Newmeyer
Keyword(s):  
Mating Type ◽  
Break Point ◽  
Low Fertility ◽  
Type Locus ◽  
Complementary Product ◽  
Single Crossing ◽  
Group I ◽  
Distinctive Morphology ◽  
Phenotype Characteristic ◽  
Break Points

Inversion In(ILR)NM176 has one break point at the extreme right end of linkage group I and the other distal to mating type in the left arm. In crosses of Inversion × Normal the products of single crossing over within the inversion are complementary duplication-deficiency classes. One crossover product is viable, with a large segment of IL duplicated and the dispensable right tip presumably deficient. This class has low fertility and distinctive morphology. The complementary product has a large deficiency which results in a pair of white, inviable ascospores. Single exchanges within the heterozygous inversion thus produce asci with 6 Black: 2 White spores; four-strand double exchanges produce 4 B:4 W; and non-exchanges produce asci with 8 B:0 W. Approximate mapping of break points was accomplished by three-point crosses. Precise placement of the left break point between ser-3 and un(55701t), just left of mating type, is based on coverage of markers by the heterozygous duplication. No crossover has been obtained between mating type and the break point, despite extensive efforts. In(ILR)NM176 differs from the inversion In(ILR)H4250 described by Newmeyer and Taylor (1967) in one main respect: the mating type locus is included in the inverted segment of NM176. Consequently, when duplications are generated, the progeny are unisexual and do not have the unstable inhibited phenotype characteristic of H4250 duplication progeny, which are heterozygous for the mating type alleles A and a. Three other inversions which originated independently of In(ILR)NM176 resemble it closely and have similar or identical break points.

scholarly journals A GENETIC MAP OF DICTYOSTELIUM DISCOIDEUM BASED ON MITOTIC RECOMBINATION

Genetics ◽  
1982 ◽  
Vol 102 (4) ◽  
pp. 691-710
Author(s):  
Dennis L Welker ◽  
Keith L Williams
Keyword(s):  
Dictyostelium Discoideum ◽  
Genetic Map ◽  
Mating Type ◽  
Cellular Slime Mold ◽  
Linkage Groups ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Group I ◽  
Slime Mold Dictyostelium Discoideum ◽  
Cellular Slime

ABSTRACT A genetic map of the cellular slime mold Dictyostelium discoideum is presented in which 42 loci are ordered on five of the seven linkage groups. Although most of the loci were ordered using standing mitotic crossing-over techniques in which recessive selective markers were employed, use was also made of unselected recombined haploid strains. Consistent with cytological studies in which the chromosomes appear to be acrocentric, only a single arm has been found for each of the five linkage groups studied. The mating-type locus, matA, has been located in the tsgE-sprA interval on linkage group I on the basis of studies on diploids formed between strains of opposite mating type that have escaped from vegetative incompatibility.

scholarly journals Genetic Diversity of the Mating Type and Toxin Production Genes in Pyrenophora tritici-repentis

2010 ◽  
Vol 100 (5) ◽  
pp. 474-483 ◽  
Author(s):  
P. Lepoint ◽  
M.-E. Renard ◽  
A. Legrève ◽  
E. Duveiller ◽  
H. Maraite
Keyword(s):  
Mating Type ◽  
Production Capacity ◽  
Toxin Production ◽  
Tan Spot ◽  
Single Individual ◽  
Type Locus ◽  
Pyrenophora Tritici Repentis ◽  
Group I ◽  
Group Ii ◽  
Race Identification

Pyrenophora tritici-repentis, the causal agent of tan spot on wheat, is a homothallic loculoascomycete with a complex race structure. The objectives of this study were to confirm the homothallic nature of the pathogen, characterize mating type diversity and toxin production genes in a global collection of strains, and analyze how these traits are associated between each other and with existing races. The pseudothecia production capacity, race identification, mating type locus (MAT), internal transcribed spacer, and glyceraldehyde-3-phosphate dehydrogenase regions were analyzed in a selection of 88 strains originating from Europe, North and South America, North Africa, and Central and South Asia. Some (60%) strains produced pseudothecia containing ascospores, independent of their origin. Race identification obtained using the multiplex polymerase chain reaction targeting host-selective toxin (HST) genes was consistent, overall, with the results based on the inoculation of a set of differential wheat cultivars and confirmed the predominance of race 1/2 strains (≈83%). However, discrepancies in race identification, differences from the reference tester strains, and atypical ToxA profiles suggest the presence of new races and HSTs. The MAT1-1 and MAT1-2 coding regions are consecutively arranged in a single individual, suggesting putative heterothallic origin of P. tritici-repentis. Upstream from the MAT is an open reading frame of unknown function (ORF1) containing a MAT-specific degenerate carboxy-terminus. The phylogenetic analysis of the MAT locus reveals two distinct groups, unlinked to geographical origin or ToxA profile. Group I, the best-represented group, is associated with typical tan spot lesions caused by races 1, 2, 3, and 5 on wheat. It is more homogenous than group II encompassing race 4 strains, as well as isolates associated primarily with small spot lesions on wheat leaves or other hosts. Group II could contain several distinct taxa.

scholarly journals THE INSTABILITY OF NEUROSPORA DUPLICATION Dp(IL⇒IR)H4250, AND ITS GENETIC CONTROL

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 461-487
Author(s):  
Dorothy Newmeyer ◽  
Donna R Galeazzi
Keyword(s):  
Mating Type ◽  
Pericentric Inversion ◽  
Crossing Over ◽  
Chromosome Break ◽  
Vegetative Incompatibility ◽  
Type Locus ◽  
Normal Sequence ◽  
Two Factors ◽  
Break Points ◽  
As If

ABSTRACT Previous work (Newmeyer and Taylor 1967) showed that a nontandem duplication, Dp(IL→IR)H4250, is regularly produced by recombination in crosses heterozygous for the effectively terminal pericentric inversion In(IL→IR)H4250. The duplications initially have strongly inhibited growth because they are heterozygous for mating type, which behaves like a vegetative-incompatibility (het) locus. Such cultures "escape" from the inhibition as a result of events that eliminate the mating-type heterozygosity. The product of a given escape event may be barren or fertile. (Neurospora duplications are characteristically barren; that is, when crossed, they make many perithecia but few ascospores.)—The present paper reports on a genetic analysis of the instability of Dp(IL→IR)H4250 . Most of the barren escape products behave as if due either to mitotic crossovers, which make mating type and distal markers homozygous, or to very long deletions which uncover mating type and all distal markers; presumably the latter would retain enough duplicated material to render them barren. It is difficult to distinguish between these two possibilities, but homozygosis seems more probable and has been clearly demonstrated in one case. Only a few barren escapes could be due to short deletions or to changes at the mating-type locus.—The fertile escape products appear to be euploid. Most of these behave as if they arose by precise deletion of one or the other duplicated segment, thus restoring one of the parental sequences. A large majority of the precise deletions restore normal sequence; only a few restore inversion sequence. Preferential restoration of the normal sequence has also been found by other workers for Neurospora duplications from several other rearrangements. A hypothesis is presented to explain these findings; it is posulated that the precise deletions result from mitotic crossing over in homologous material located at chromosome tips and tip-break-points.—There is a smaller group of fertile escapes that are unlike either parental sequence; at least one of these involves a chromosome break outside the duplicated region.—Duplications in which the vegetative incompatibility is suppressed by the unlinked modifier tol are extremely barren; they only rarely lose a duplicated segment so as to become fertile.—The instability of Dp(IL→IR)H4250, with and without tol, is markedly altered by factors in the genetic background. The two factors studied in detail have qualitatively different effects.

scholarly journals MEIOSIS IN NEUROSPORA CRASSA. I. THE ISOLATION OF RECESSIVE MUTANTS DEFECTIVE IN THE PRODUCTION OF VIABLE ASCOSPORES

Genetics ◽  
1980 ◽  
Vol 96 (2) ◽  
pp. 367-378
Author(s):  
A M DeLange ◽  
A J F Griffiths
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Selection Procedure ◽  
Class I ◽  
Sexual Cycle ◽  
Class Iii ◽  
Type Locus ◽  
Group I ◽  
Normal Production ◽  
Class Iib

ABSTRACT A scheme has been devised for efficient isolation of recessive meiotic mutants of Neurospora crassa. These mutants were detected by their reduced fertility or by the abortion of ascospores. Their isolation involved the selection and screening of strains arising from ascospores disomic (n + 1) for linkage group I (LG I), which bears the mating-type locus. These strains are self-fertile heterokaryons that contain two types of haploid nuclei of opposite mating type (A + a). Selfings of these strains are homozygous for genes on all linkage groups except LGI and therefore allow the expression of recessive mutants with an altered sexual cycle. Using this selection procedure, three classes of mutants were detected. In one class, mutants had an early block in perithecial development (class I), and in another mutants had altered perithecia, but apparently unaltered fertility (class III). No recessive mutants were observed and all mutants tested (eight of class I and two of class III) were expressed only when used as the maternal parent. A third mutant class displayed normal production of perithecia, but defective formation of asci (class IIA), or black ascospores (class IIB). Four of 13 class IIA mutants were analyzed, and two of them [asc(DL131) and asc(DL400)] were definitely recessive. Analysis of 10 of 13 class IIB mutants disclosed six recessive, mutually complementing mutants: asc(DL95), asc(DL243), asc(DL711), asc(DL879), asc(DL917m) and asc(DL961). Mutants asc(DL95), asc(DL243) and the previously studied mei-1 mutant (Smith 1975) complemented one another in crosses, but did not recombine. These may be alleles of the same gene, or they may comprise a gene cluster.

scholarly journals Mating Type in Chlamydomonas Is Specified by mid, the Minus-Dominance Gene

Genetics ◽  
1997 ◽  
Vol 146 (3) ◽  
pp. 859-869 ◽  
Author(s):  
Patrick J Ferris ◽  
Ursula W Goodenough
Keyword(s):  
Transcription Factor ◽  
Mating Type ◽  
Codon Bias ◽  
Leucine Zipper ◽  
Laboratory Strain ◽  
Leucine Zipper Motif ◽  
Type Locus ◽  
Diploid Cells ◽  
Necessary And Sufficient

Diploid cells of Chlamydomonas reinhardtii that are heterozygous at the mating-type locus (mt  +/mt  –) differentiate as minus gametes, a phenomenon known as minus dominance. We report the cloning and characterization of a gene that is necessary and sufficient to exert this minus dominance over the plus differentiation program. The gene, called mid, is located in the rearranged (R) domain of the mt  – locus, and has duplicated and transposed to an autosome in a laboratory strain. The imp11 mt  – mutant, which differentiates as a fusion-incompetent plus gamete, carries a point mutation in mid. Like the fus1 gene in the mt  + locus, mid displays low codon bias compared with other nuclear genes. The mid sequence carries a putative leucine zipper motif, suggesting that it functions as a transcription factor to switch on the minus program and switch off the plus program of gametic differentiation. This is the first sex-determination gene to be characterized in a green organism.

scholarly journals THE SEARCH FOR MATING-TYPE-LIMITED GENES IN THE HOMOTHALLIC ALGA CHLAMYDOMONAS MONOICA

Genetics ◽  
1986 ◽  
Vol 113 (3) ◽  
pp. 601-619
Author(s):  
Karen P VanWinkle-Swift ◽  
Jang-Hee Hahn
Keyword(s):  
Mating Type ◽  
Resistance Mutation ◽  
Mendelian Inheritance ◽  
Sexual Cycle ◽  
Uniparental Inheritance ◽  
Cell Type ◽  
Erythromycin Resistance ◽  
Type Locus ◽  
Heterothallic Species ◽  
Chlamydomonas Monoica

ABSTRACT The non-Mendelian erythromycin resistance mutation ery-u1 shows bidirectional uniparental inheritance in crosses between homothallic ery-u1 and ery-u1  + strains of Chlamydomonas monoica. This inheritance pattern supports a general model for homothallism invoking intrastrain differentiation into opposite compatible mating types and, further, suggests that non-Mendelian inheritance is under mating-type (mt) control in C. monoica as in heterothallic species. However, the identification of genes expressed or required by one gametic cell type, but not the other, is essential to verify the existence of a regulatory mating-type locus in C. monoica and to understand its role in cell differentiation and sexual development. By screening for a shift from bidirectional to unidirectional transmission of the non-Mendelian ery-u1 marker, a mutant with an apparent mating-type-limited sexual cycle defect was obtained. The responsible mutation, mtl-1, causes a 1000-fold reduction in zygospore germination in populations homozygous for the mutant allele and, approximately, a 50% reduction in germination for heterozygous (mtl-1/mtl-1  +) zygospores. By next screening for strains unable to yield any viable zygospores in a cross to mtl-1, a second putative mating-type-limited mutant, mtl-2, was obtained. The mtl-2 strain, although self-sterile, mates efficiently with mtl-2  + strains and shows a unidirectional uniparental pattern of inheritance for the ery-u1 cytoplasmic marker, similar to that observed for crosses involving mtl-1. Genetic analysis indicates that mtl-1 and mtl-2 define unique unlinked Mendelian loci and that the sexual cycle defects of reduced germination (mtl-1) or self-sterility (mtl-2) cosegregate with the effect on ery-u1 cytoplasmic gene transmission. By analogy to C. reinhardtii, the mtl-1 and mtl-2 phenotypes can be explained if the expression of these gene loci is limited to the mt  + gametic cell type, or if the wild-type alleles at these loci are required for the normal formation and/or functioning of mt  + gametes only.

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