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Journal of Biosciences

, Volume 42, Issue 1, pp 15–21 | Cite as

Neurospora tetrasperma crosses heterozygous for hybrid translocation strains produce rare eight-spored asci-bearing heterokaryotic ascospores

  • Durgadas P Kasbekar
  • Selvam Rekha
Article

Abstract

During ascogenesis in Neurospora, the ascospores are partitioned at the eight-nucleus stage that follows meiosis and a post-meiotic mitosis, and the ascospores that form in eight-spored asci are usually homokaryotic. We had previously created novel T Nt strains by introgressing four Neurospora crassa insertional translocations (EB4, IBj5, UK14-1, and B362i) into N. tetrasperma. We now show that crosses of all the T Nt strains with single-mating-type derivatives of the standard N. tetrasperma pseudohomothallic strain 85 (viz. T Nt a × 85A or T Nt A × 85a) can produce rare eight-spored asci that contain heterokaryotic ascospores, or ascospores with other unexpected genotypes. Our results suggest that these rare asci result from the interposition of additional mitoses between the post-meiotic mitosis and the partitioning of nuclei into ascospores, leading to the formation of supernumerary nuclei that then generate the heterokaryotic ascospores. The rare asci probably represent a background level of ascus dysgenesis wherein the partitioning of ascospores becomes uncoupled from the post-meiotic mitosis. Ordinarily, the severest effect of such dysgenesis, the production of mating-type heterokaryons, would be suppressed by the N. crassa tol (tolerant) gene, thus explaining why such dysgenesis remained undetected thus far.

Keywords

Heterokaryotic ascospores Neurospora tetrasperma 

Notes

Acknowledgements

We thank the Fungal Genetics Stock Center, Kansas State University, Manhattan, Kansas USA, for maintaining the strains. DPK holds the Haldane Chair of the Centre for DNA Fingerprinting and Diagnostics (CDFD). This research was supported by CDFD Core Funds, and Grant SB/SO/BB-0111/2013, from the Department of Science and Technology, India.

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Copyright information

© Indian Academy of Sciences 2017

Authors and Affiliations

  1. 1.Centre for DNA Fingerprinting and DiagnosticsHyderabadIndia

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