Inheritance of DNA-induced inositol independence of inositolless Neurospora crassa.

Abstract

Neurospora crassa (N. crassa) inositolless (inl) strain gives inositol-independent colonies (inl+) if treated with DNA from wild type N. crassa. There is an increased number of unusual non-Mendelian tetrads (24%) among the progeny. In sexual crosses of these strains with inl alleles ascospores of complete ordered tetrads were isolated. Clones of these aberrant tetrads were examined for the inheritance of the inl+ and inl markers respectively. Several inl+ clones of single ascospores of these tetrads were often pseudowild types. These clones segregate inl+ and inl nuclei if growing on inositol-containing (complete) medium and the inl+ character shows somatic segregation, sometimes disappears very quickly. The transformed inl+ chromosomes is occasionally passed on to the next generation in sexual cross, but the ascospores are of two kinds: inl+ and pseudowild type inl+. The inl+ trait is transmitted to further generations though the ascospores of the next generation have often lower germination rate. The pseudowild types in sexual cross are sterile on minimal medium and segregate very quickly inl nuclei. The mechanism of the origin of pseudowild types is assumed to be diploidization and consequently disomy of chromosome 2.