Deletion of the MAT-2 mating-type gene during uni-directional mating-type switching in Ceratocystis

• Published in: Current genetics Vol. 38; no. 1; pp. 48 - 52
• Main Authors: Witthuhn, R C, Harrington, T C, Wingfield, B D, Steimel, J P, Wingfield, M J
• Format: Journal Article
• Language: English
• Published: United States 01.07.2000
• Subjects: Amino Acid Sequence; Ascomycota - genetics; Binding Sites; Ceratocystis eucalypti; Ceratocystis fimbriata; Ceratocystis pinicola; Ceratocystis virescens; Crosses, Genetic; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; Fungal Proteins - chemistry; Fungal Proteins - genetics; Gene Deletion; Genes, Fungal; High Mobility Group Proteins - chemistry; High Mobility Group Proteins - genetics; MAT-2 gene; Molecular Sequence Data; Sequence Alignment; Sequence Homology, Amino Acid
• ISSN: 0172-8083; 1432-0983
• DOI: 10.1007/s002940000131

Ceratocystis eucalypti is strictly heterothallic, with single ascospore strains representing one of two opposite mating types. Most other Ceratocystis species, including C. virescens, C. pinicola, and C. fimbriata, are homothallic. In the homothallic species, the MAT-2 strains are self-fertile, while MAT-1 strains are self-sterile and grow more slowly than MAT-2 strains. The current hypothesis is that self-fertility of MAT-2 strains is due to the deletion of the MAT-2 mating-type gene, resulting in the expression of the MAT-1 mating type. These mutant MAT-1 strains are able to cross with MAT-2 strains. Part of the MAT-2 mating-type gene in C. eucalypti, C. pinicola, and C. fimbriata was amplified using degenerate primers designed from the conserved MAT-2 HMG DNA-binding motif. The expected approximately 300-bp PCR products were cloned and sequenced. Specific primers were designed that amplified 210-bp fragments only in MAT-2 isolates of C. eucalypti, C. virescens, C. pinicola, and C. finbriata. These fragments were present in self-fertile field isolates and self-fertile progeny but were absent in the self-sterile (MAT-1) progeny from selfings of C. virescens, C. pinicola, and C. fimbriata, thus supporting the hypothesis that the MAT-2 mating-type gene is deleted during uni-directional mating-type switching. A Southern-blot analysis was performed to confirm the deletion of MAT-2 gene in self-sterile progeny. The DNA sequence data for the C. eucalypti MAT-2 mating-type gene was increased to 1371-bp using TAIL-PCR and uneven PCR, representing a portion of the complete MAT-2 gene DNA sequence.