title: DNA loss at the Ceratocystis fimbriata mating locus results in self-sterility.
abstract: Fungi have evolved a remarkable diversity of reproductive strategies. Some of these, most notably those of the model fungi, have been well studied but others are poorly understood. The latter is also true for uni-directional mating type switching, which has been reported in only five fungal genera, including Ceratocystis. Mating type switching allows a self-fertile fungal isolate to produce both self-fertile and self-sterile offspring. This study considered the molecular nature of uni-directional mating type switching in the type species of Ceratocystis, C. fimbriata. To do this, the genome of C. fimbriata was first examined for the presence of mating type genes. Three mating genes (MAT1-1-1, MAT1-2-1 and MAT1-1-2) were found in an atypical organisation of the mating type locus. To study the effect that uni-directional switching has on this locus, several self-sterile offspring were analysed. Using a combination of next generation and conventional Sanger sequencing, it was shown that a 3581 base pair (bp) region had been completely deleted from the MAT locus. This deletion, which includes the entire MAT1-2-1 gene, results in the permanent loss of self-fertility, rendering these isolates exclusively self-sterile. Our data also suggest that the deletion mechanism is tightly controlled and that it always occurs at the same genomic position. Two 260 bp direct repeats flanking the deleted region are strongly implicated in the process, although the exact mechanism behind the switching remains unclear.
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: P Markus
authors.initials: PM
authors.lastname: Wilken
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Emma T
authors.initials: ET
authors.lastname: Steenkamp
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wingfield
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Z Wilhelm
authors.initials: ZW
authors.lastname: de Beer
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa.
authors.forename: Brenda D
authors.initials: BD
authors.lastname: Wingfield
mesh_terms: D001203:Ascomycota / Q000235:genetics* / Q000302:isolation & purification; D020029:Base Pairing / Q000235:genetics; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics*; D005298:Fertility / Q000235:genetics; D049770:Genes, Mating Type, Fungal; D056426:Genetic Loci; D008969:Molecular Sequence Data; D059372:Nucleotide Motifs / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics
chemical_list: D004271:DNA, Fungal