A search for temperature-sensitive mutants of<i>Ustilago maydis</i>blocked in DNA synthesis

Unrau, P.; Holliday, Robin

doi:10.1017/s001667230000149x

Cited by 36 publications

(16 citation statements)

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“…The cdc45 ts mutant used in these studies was originally known as ts-92 (Unrau and Holliday 1970) and then subsequently named tsd2-1 before the gene product was known to be orthologous to Cdc45 (Onel and Holloman 1997). Cdc45 will henceforth replace the name Tsd2.…”

Section: U Maydis Strains and Genetic Methodsmentioning

confidence: 99%

“…The mutant grows robustly at 22°but is severely crippled at 32°( Figure 1B). In an early study of this mutant it was determined that over a period of 6 hr after shifting cell cultures to 32°, the relative increase in DNA synthesis in the mutant was only about 10% compared to wild type (Unrau and Holliday 1970). In addition, approximately half the cells in the population were no longer viable after 8 hr.…”

Section: Teliospore Germination During Inhibition Of Dna Replicationmentioning

confidence: 99%

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Initiation of Meiotic Recombination in Ustilago maydis

et al. 2013

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A central feature of meiosis is the pairing and recombination of homologous chromosomes. Ustilago maydis, a biotrophic fungus that parasitizes maize, has long been utilized as an experimental system for studying recombination, but it has not been clear when in the life cycle meiotic recombination initiates. U. maydis forms dormant diploid teliospores as the end product of the infection process. Upon germination, teliospores complete meiosis to produce four haploid basidiospores. Here we asked whether the meiotic process begins when teliospores germinate or at an earlier stage in development. When teliospores homozygous for a cdc45 mutation temperature sensitive for DNA synthesis were germinated at the restrictive temperature, four nuclei became visible. This implies that teliospores have already undergone premeiotic DNA synthesis and suggests that meiotic recombination initiates at a stage of infection before teliospores mature. Determination of homologous recombination in plant tissue infected with U. maydis strains heteroallelic for the nar1 gene revealed that Nar + recombinants were produced at a stage before teliospore maturation. Teliospores obtained from a spo11D cross were still able to germinate but the process was highly disturbed and the meiotic products were imbalanced in chromosomal complement. These results show that in U. maydis, homologous recombination initiates during the infection process and that meiosis can proceed even in the absence of Spo11, but with loss of genomic integrity. M EIOSIS has long held fascination for evolutionary biologists, cytologists, and geneticists alike by the puzzle of its evolutionary origin, the chromosome choreography, and its role in generating genetic diversity (Wilkins and Holliday 2009). The distinctive events of meiosis include pairing of homologs along their entire lengths, extensive recombination between homologs, suppression of sisterchromatid separation in the first division, and absence of S phase at the start of the second division. Attention of geneticists has centered primarily on the second step-namely genetic recombination during pairing and its function in maintaining genomic integrity and in generating new linkage relationships among genes. As reciprocal recombination events are essential for proper chromosome segregation at the first meiotic division, this process has profound implications in human development and health (Nagaoka et al. 2012). The central question of how homologous chromosomes recognize each other and pair to enable recombination has provoked a great deal of research in a variety of experimental systems. Certain core principles underlie the process, but there is enormous variation in mechanical operations and regulatory mechanisms from one organism to the next and uncertainty in how DNA information is used for pairing and recombination (Pawlowski et al. 2007;Schvarzstein et al. 2010;Storlazzi et al. 2010;Tsai and Mckee 2011;Lake and Hawley 2012). Thus, to geneticists the study of meiosis is irresistibly interesting.Ustila...

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Section: U Maydis Strains and Genetic Methodsmentioning

confidence: 99%

Section: Teliospore Germination During Inhibition Of Dna Replicationmentioning

confidence: 99%

Initiation of Meiotic Recombination in Ustilago maydis

et al. 2013

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“…1) A number of studies have been reported on the chemical constituents of C. pulcherrima. [2][3][4][5][6][7][8][9][10][11] We have previously reported the isolation of four new furanoid diterpenes from the leaves of the plant. 12) We report here the isolation and structure elucidation of another new furanoid diterpene dibenzoate (1) from the leaves of the plant and the known compounds caesaldekarin A (3), spathulenol (4), caryophyllene oxide (5), phytol, and sitosterol.…”

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confidence: 99%

A New Furanoid Diterpene from Caesalpinia pulcherrima

et al. 2003

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“…The isolation and preliminary characterization of temperature-sensitive mutants of Ustilago maydis has been described (Unrau and Holliday, 1970). Holliday (1974) has recently reviewed genetic and other methods in this organism.…”

Section: Methodsmentioning

confidence: 99%

“…A series of temperature-sensitive mutants of Ustilago blocked in DNA synthesis have been partially described (Unrau and Holliday, 1970;Unrau and Holliday, 1972) and some eight mutants so blocked are now known. One of these mutants was found to have a temperature-sensitive DNA polymerase (Jeggo et al, 1973) and is being characterized for its effects on recombination and repair (Unrau and Olive, 1973).…”

Section: Introductionmentioning

confidence: 99%

Differential chromosomal and mitochondrial DNA synthesis in temperature-sensitive mutants ofUstilago maydis

Unrau¹

1977

Molec. Gen. Genet.

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The amount and type of residual DNA synthesis was determined in eight temperature-sensitive mutants of the smut fungus Ustilago maydis after incubation at the restrictive temperature (32 degrees C) for eight hours. Mutants ts-220, ts-207, ts-432 and ts-346 were found to have an overall reduction in the synthesis of both nuclear and mitochondrial DNA comparison to the wild-type. In mutants ts-20, tsd 1-1, ts-84 and pol 1-1 nuclear DNA synthesis was depressed relative to mitochondrial synthesis. The DNA-polymerase mutant pol 1-1 had persistent nuclear synthesis at about 50% of the rate of synthesis of mitochondrial DNA and similar behavior was observed in a diploid homozygous strain. Mutant ts-84 had an initial burst of DNA synthesis which was reduced for nuclear but not mitochondrial synthesis after three hours preincubation at 32 degrees C. tsd 1-1 and ts-20 had nuclear residual synthesis amounting to about 25% of the relative rate of mitochondrial synthesis which correlates to increasing UV sensitivity of these strains on incubation at 32 degrees C. A pol 1-1 ts-84 double mutant had an additive loss of nuclear DNA synthesis which indicates that the steps of replication involved may be sequential.

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A search for temperature-sensitive mutants ofUstilago maydisblocked in DNA synthesis

Cited by 36 publications

References 31 publications

Initiation of Meiotic Recombination in Ustilago maydis

Initiation of Meiotic Recombination in Ustilago maydis

A New Furanoid Diterpene from Caesalpinia pulcherrima

Differential chromosomal and mitochondrial DNA synthesis in temperature-sensitive mutants ofUstilago maydis

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