Hostname: page-component-586b7cd67f-tf8b9 Total loading time: 0 Render date: 2024-11-23T01:15:32.388Z Has data issue: false hasContentIssue false
  • English
  • Français

A buff spore colour mutant in Sordaria brevicollis showing high-frequency conversion

1. Characteristics of the mutant

Published online by Cambridge University Press:  14 April 2009

Mary V. Macdonald  and
Harold L. K. Whitehouse
Mary V. Macdonald
Affiliation:
Botany School, University of Cambridge, Downing Street, Cambride CB2 3EA
Harold L. K. Whitehouse
Affiliation:
Botany School, University of Cambridge, Downing Street, Cambride CB2 3EA
Rights & Permissions [Opens in a new window]

Summary

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A mutant, YS17, at the buff spore colour locus in Sordaria brevicollis, when crossed with wild type, gives rise to aberrant asci with a frequency over 10 times that of other buff mutants. Over 98% of the aberrant asci have 6 wild type and 2 mutant spores. From tests with another buff mutant it is concluded that loss of the mutant spore colour when YS17 shows conversion to wild type is associated with loss of the high frequency conversion, and that both characters are caused by the same mutation. A methionine-requiring mutant (met-1) has been obtained that maps 5 units to the left of buff, and this, together with the nicotinamide-requiring mutant (nic-1) 2 units to the right, has provided flanking markers for buff that can be scored with complete reliability. Crosses between YS17 and 28 other buff mutants have revealed close linkage to three of them which map to its right on the basis of flanking marker behaviour, all the others mapping to its left. The frequency of postmeiotic segregation at the sites of buff mutants near to the site of YS17 is greatly increased in the presence of YS17, and occurs in the chromatid showing conversion to wild type at YS17.

From these and other results, obtained largely by ascus analysis, the following conclusions have been drawn.

(1) The YS17 mutation is probably acting as a recognition site for an endonuclease that initiates recombination, with the result that the frequency of heteroduplex DNA within the buff gene is much increased.

(2) The recombination initiated at YS17 is asymmetric (or at least pre-dominantly so), with the YS17 site acting as a recipient of a nucleotide chain from the other parent, not a donor to it.

(3) The frequency of crossing over associated with conversion at YS17 is variable: about 30% in crosses with most of the buff mutants, about half this value in crosses with wild type, and almost zero in crosses with closely-linked buff mutants.

(4) In about one third of the crossover asci in crosses between YS17 and other buff mutants the crossover is not adjacent to the site of YS17 but separated from it by the site of the allele, which shows normal 4:4 segregation.

(5) It seems necessary to revive the idea of more than one recombination event in proximity, a non-crossover conversion event sometimes leading to a second event – a crossover – in the vicinity. It is tentatively suggested that both might be controlled by a single enzyme aggregate.

Type
Research Article
Information
Genetics Research , Volume 34 , Issue 2 , October 1979 , pp. 87 - 119
Copyright
Copyright © Cambridge University Press 1979

References

REFERENCES

Ahmad, A. F. (1975). The effects of temperature on aberrant ascus frequencies at the buff locus in Sordaria brevicollis. Genetical Research 26, 127–135.CrossRefGoogle Scholar
Angel, T., Austin, B. & Catcheside, D. G. (1970). Regulation of recombination at the his-3 locus in Neurospora crassa. Australian Journal of Biological Sciences 23, 1229–1240CrossRefGoogle ScholarPubMed
Bandiera, M., Armaleo, D. & Morpurgo, G. (1973). Mitotic intragenic recombination as a consequence of heteroduplex formation in Aspergillus nidulans. Molecular and General Genetics 122, 137–148.CrossRefGoogle ScholarPubMed
Bond, D. J. (1973). Polarity of gene conversion and postmeiotic segregation at the buff locus in Sordaria brevicollis. Genetical Research 22, 279–289.CrossRefGoogle ScholarPubMed
Carlson, P. S. (1971). A genetic analysis of the rudimentary locus of Drosophila melanogaster. Genetical Research 17, 53–81.CrossRefGoogle Scholar
Catcheside, D. G. (1977). The Genetics of Recombination. London: Arnold.Google Scholar
Catcheside, D. G. & Angel, T. (1974). A histidine-3 mutant in Neurospora crassa due to an interchange. Australian Journal of Biological Sciences 27, 219–229.CrossRefGoogle Scholar
Emerson, S. & Yu-Sun, C. C. C. (1967). Gene conversion in the Pasadena strain of Ascobolus immersus. Genetics 55, 39–47.CrossRefGoogle ScholarPubMed
Esposito, M. S. (1978). Evidence that spontaneous mitotic recombination occurs at the two-strand stage. Proceedings of the National Academy of Sciences of the U.S.A. 75, 4436–4440.CrossRefGoogle ScholarPubMed
Fincham, J. R. S. (1974). Negative interference and the use of flanking markers in finestructure mapping in Fungi. Heredity 33, 116–121.CrossRefGoogle Scholar
Fink, G. R. (1974). Properties of gene conversion of deletions in Saccharomyces cerevisiae. In Mechanisms in Recombination, (ed. Grell, R. F.), pp. 287–293. New York and London: Plenum.CrossRefGoogle Scholar
Fink, G. R. & Styles, L. A. (1974). Gene conversion of deletions in the his 4 region of yeast. Genetics 77, 231–244.CrossRefGoogle Scholar
Fogel, S. & Hurst, D. D. (1967). Meiotic gene conversion in yeast tetrads and the theory of recombination. Genetics 57, 455–481.CrossRefGoogle ScholarPubMed
Fogel, S., Hurst, D. D. & Mortimer, R. K. (1971). Gene conversion in unselected tetrads from multipoint crosses. Stadler Symposium 1/2, 89–110.Google Scholar
Friedman, L. R. & Sobell, H. M. (1978). Evidence for asymmetric initiation of recombination in yeast: radiation induced asymmetries in mitotic recombination. Manuscript.Google Scholar
Gutz, H. (1971). Site specific induction of gene conversion in Schizosaccharomyces pombe. Genetics 69, 317–337.CrossRefGoogle ScholarPubMed
Lamb, B. C. (1969). Evidence from Sordaria that recombination and conversion frequencies are partly determined before meiosis, and for a general model of the control of recombination frequencies. Genetics 63, 807–820.CrossRefGoogle ScholarPubMed
Lamb, B. C. & Helmi, S. (1978). A new type of genetic control of gene conversion, from Ascobolus immersus. Genetical Research 32, 67–78.CrossRefGoogle Scholar
Lamb, B. C. & Wickramaratne, M. R. T. (1973). Corresponding-site interference, synaptinemal complex structure, and 8+: 0m and 7+: 1m octads from wild type × mutant crosses of Ascobolus immersus. Genetical Research 22, 113–124.CrossRefGoogle Scholar
Lawrence, C. W., Sherman, F., Jackson, M. & Gilmore, R. A. (1975). Mapping and gene conversion studies with the structural gene for iso-1-cytochrome c in yeast. Genetics 81, 615–629.CrossRefGoogle ScholarPubMed
Leblon, G. (1972 a). Mechanism of gene conversion in Ascobolus immersus. I. Existence of a correlation between the origin of mutants induced by different mutagens and their conversion spectrum. Molecular and General Genetics 115, 36–48.CrossRefGoogle Scholar
Leblon, G. (1972 b). Mechanism of gene conversion in Ascobolus immersus. II. The relationships between the genetic alterations in b1 or b2 mutants and their conversion spectrum. Molecular and General Genetics 116, 322–335.CrossRefGoogle ScholarPubMed
MacDonald, M. V., Sang, H. M. & Whitehouse, H. L. K. (1979). Recombination at spore colour loci in Sordaria. Proceedings of the Fourteenth International Congress of Genetics,Moscow, 1978. (In the press.)Google Scholar
Meselson, M. S. & Radding, C. M. (1975). A general model for genetic recombination. Proceedings of the National Academy of Sciences of the U.S.A. 72, 358–361.CrossRefGoogle ScholarPubMed
Paquette, N. & Rossignol, J.-L. (1978). Gene conversion spectrum of 15 mutants giving post-meiotic segregation in the b2 locus of Ascobolus immersus. Molecular and General Genetics 163, 313–326.CrossRefGoogle Scholar
Pritchard, R. H. (1960). Localized negative interference and its bearing on models of gene recombination. Genetical Research 1, 1–24.CrossRefGoogle Scholar
Rossignol, J.-L. & Haedens, V. (1978). The interaction during recombination between closely linked allelic frameshift mutant sites in Ascobolus immersus. 1. A (or B) and C type mutant sites. Heredity 40, 405–425,CrossRefGoogle Scholar
Sang, H. & Whitehouse, H. L. K. (1979 a). Genetic recombination at the buff spore colour locus in Sordaria brevicollis. I. Analysis of flanking marker behaviour in crosses between buff mutants and wild type. Molecular and General Genetics 174, 327–334.CrossRefGoogle Scholar
Sang, H. & Whitehouse, H. L. K. (1979 b). Genetic recombination at the buff spore colour locus in Sordaria brevicollis. II. Analysis of flanking marker behaviour in crosses between buff mutants. Manuscript in preparation.CrossRefGoogle Scholar
Whitehouse, H. L. K. & Hastings, P. J. (1965). The analysis of genetic recombination on the polaron hybrid DNA model. Genetical Research 6, 27–92.CrossRefGoogle ScholarPubMed
Wickramaratne, M. R. T. (1976). A method for selecting linked markers in Sordaria brevicollis. Neurospora Newsletter 23, 27–28.Google Scholar
Yu-Sun, C. C., Wickramaratne, M. R. T. & Whitehouse, H. L. K. (1974). Conversion spectrum of Sordaria brevicollis mutants induced by different mutagens. Heredity 33, 453–454 (Abstract).Google Scholar
Yu-Sun, C. C., Wickramaratne, M. R. T. & Whitehouse, H. L. K. (1977). Mutagen specificity in conversion pattern in Sordaria brevicollis. Genetical Research 29, 65–81.CrossRefGoogle Scholar