title: Neurospora Heterokaryons with Complementary Duplications and Deficiencies in Their Constituent Nuclei Provide an Approach to Identify Nucleus-Limited Genes.
abstract: Introgression is the transfer of genes or genomic regions from one species into another via hybridization and back-crosses. We have introgressed four translocations (EB4, IBj5, UK14-1, and B362i) from Neurospora crassa into N. tetrasperma. This enabled us to construct two general types of heterokaryons with mat-A and mat-a nuclei of different genotypes: one type is [T + N] (with one translocation nucleus and one normal sequence nucleus), and the other is [Dp + Df] (with one nucleus carrying a duplication of the translocation region and the other being deleted for the translocation region). Self-crossing these heterokaryons again produced [T + N] and [Dp + Df] progeny. From conidia (vegetative spores) produced by the heterokaryotic mycelia, we obtained self-fertile (heterokaryotic) and self-sterile (homokaryotic) derivative strains. [T + N] heterokaryons produced homokaryotic conidial derivatives of both mating types, but [Dp + Df] heterokaryons produced viable conidial homokaryons of only the mating type of the Dp nucleus. All four [T + N] heterokaryons and three [Dp + Df] heterokaryons produced both self-sterile and self-fertile conidial derivatives, but the [Dp(B362i) + Df(B362i)] heterokaryons produced only self-sterile ones. Conceivably, the Df(B362i) nuclei may be deleted for a nucleus-limited gene required for efficient mitosis or nuclear division, and whose deficit is not complemented by the neighboring Dp(B362i) nuclei. A cross involving Dp(EB4) showed repeat-induced point mutation (RIP). Because RIP can occur in self-crosses of [Dp + Df] but not [T + N] heterokaryons, RIP alteration of a translocated segment would depend on the relative numbers of [Dp + Df] vs. [T + N] ancestors.
authors.affiliation: Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India Graduate Studies, Manipal University, Manipal 576104, Karnataka, India.
authors.forename: Dev Ashish
authors.initials: DA
authors.lastname: Giri
authors.affiliation: Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India.
authors.forename: S
authors.initials: S
authors.lastname: Rekha
authors.affiliation: Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500001, India kas@cdfd.org.in.
authors.forename: Durgadas P
authors.identifier: http://orcid.org/0000-0002-5269-8020
authors.initials: DP
authors.lastname: Kasbekar
mesh_terms: D002467:Cell Nucleus / Q000235:genetics*; D020090:Chromosome Segregation / Q000235:genetics; D003433:Crosses, Genetic; D004271:DNA, Fungal / Q000235:genetics; D005306:Fertilization / Q000235:genetics; D020440:Gene Duplication; D020868:Gene Silencing; D005800:Genes, Fungal; D005812:Genes, Switch; D005838:Genotype; D006579:Heterozygote; D008540:Meiosis; D008969:Molecular Sequence Data; D009491:Neurospora / Q000235:genetics*; D017354:Point Mutation / Q000235:genetics; D013172:Spores, Fungal / Q000235:genetics; D014178:Translocation, Genetic
chemical_list: D004271:DNA, Fungal
keywords: MSUD; RIP; chromosome translocation; introgression; pseudohomothallism