title: Ultraviolet-inactivation of conidia from heterokaryons of Neurospora crassa containing uv-sensitive mutations.
abstract: The effect of three UV-sensitive mutations of Neurospora crassa, upr-I, uvs-4 and uvs-6, on the ultraviolet-inactivation of conidia from two-component heterokaryons was investigated. In two-component heterokaryons with wild-type sensitivity to radiation inactivation, all three conidial fractions exhibited similar ultraviolet-inactivation curves. Each UV-sensitive mutation studied uniquely modified the ultraviolet-inactivation curves of conidia from two-component heterokaryons. In heterokaryons heterokaryotic for upr-I, the upr-I mutation was recessive and the repair function determined by the wild type allele was functional to some degree in homokaryotic upr-I conidia. All three conidial fractions of heterokaryons containing upr-I in both components showed increased sensitivity to ultraviolet light. The uvs-4 mutation was recessive and resulted in conidia with increased UV-sensitivity only when included in both components of a heterokaryon. Homokaryotic uvs-4 conidia, which arose from heterokaryons containing both uvs-4 and wild-type components, exhibited wild-type survival. Therefore, as with upr-I, there was a carryover the repair capability to conidia which were genetically UV-sensitive. The uvs-6 mutation, when included in one component of a two-component heterokaryon, resulted in increased UV-sensitivity of both heterokaryotic and homokaryotic uvs-6 conidia. When both components contained uvs-6, the UV-sensitivity of all three conidial fractions was increased and all showed similar inactivation curves. Thus, as with upr-I and uvs-4, there was a carryover of the wild-type repair capability to genetically uvs-6 conidia. Heterokaryon tests for complementation between two non-allelic UV-sensitive mutations showed that in heterokaryotic conidia, complete complementation occurred between upr-I and uvs-4.
mesh_terms: D002467:Cell Nucleus / Q000528:radiation effects; D004260:DNA Repair; D005808:Genes, Recessive; D005816:Genetic Complementation Test; D008040:Genetic Linkage; D005838:Genotype; D006579:Heterozygote; D006720:Homozygote; D009154:Mutation; D009491:Neurospora / Q000528:radiation effects*; D009492:Neurospora crassa / Q000528:radiation effects* / Q000648:ultrastructure; D011831:Radiation Genetics; D013172:Spores, Fungal / Q000528:radiation effects / Q000648:ultrastructure; D014466:Ultraviolet Rays