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Polarized segregation in Ascomycetes and the differential bursting of asci

Published online by Cambridge University Press:  14 April 2009

B. C. Lamb
B. C. Lamb
Affiliation:
Genetics Laboratory, Department of Botany, University of Bristol
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Polarized segregation was studied at the asco and tan spore loci of Neurospora crassa and at the gray and hyaline loci of Sordaria fimicola. Different alleles, re-isolates and temperatures of incubation of crosses were studied with the asco locus and different temperatures of incubation with the h and g loci. The mutants were crossed with the corresponding wild-types by methods giving a considerable degree of synchrony in the development of perithecia; segregation patterns were scored from perithecia at widely differing stages of ascal maturity. Significant polarized segregation was not generally observed when little or no dehiscence had occurred from a cross but usually became readily apparent as dehiscence proceeded. This indicated that the differences in frequency between the ascal classes that had previously been interpreted as showing polarized segregation at meiosis were actually due to a post-meiotic differential bursting of asci. This bursting was studied separately from the usually concurrent pigmentation of immature asci by comparing results from asci mounted in water with those from asci in the 2 M sucrose solution which was used throughout these experiments: the differential bursting produced by mounting asci in water gave similar polarized segregation results to those from natural dehiscence. A hypothesis to account for differential bursting in physiological terms was advanced and its predictions discussed. It seems likely that cases of apparent polarized segregation described in other Ascomycetes are also due to post-meiotic phenomena.

Type
Research Article
Information
Genetics Research , Volume 7 , Issue 3 , June 1966 , pp. 325 - 334
Copyright
Copyright © Cambridge University Press 1966

References

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