Molecular standardization of mating type terminology in the Gibberella fujikuroi species complex

Abstract

Mating type in the Gibberella fujikuroi species complex is controlled by a single locus with two alleles and is usually identified following sexual crosses with standard, female-fertile tester isolates. The mating type alleles have been arbitrarily designated "+" and "-" within each biological species, and the nomenclature is tied to the standard tester strains. We developed a pair of PCR primers that can be used to amplify a unique fragment of one of the mating type alleles (MAT-2) from at least seven of the biological species in this species complex. Based on the amplification pattern, we propose a replacement for the existing, arbitrary +/- terminology that is presently in use. The new terminology is based on DNA sequence similarities between the mating type allele fragments from the biological species of the G. fujikuroi species complex and the corresponding fragments from other filamentous ascomycetes.

FIG. 1

(A) PCR amplification of a putative HMG-box sequence from mating type testers of the G. fujikuroi species complex with degenerate primers NcHMG1 and NcHMG2. Lane 1, N. crassa FGSC 4066; lane 2, λ phage DNA digested by PstI; lanes 3 through 16, G. fujikuroi A-00149, A-00999, B-03852, B-03853, C-01993, C-01995, D-04853, D-04854, E-00990, E-02192, F-04093, F-04094, G-05111, and G-05112, respectively. (B) PCR amplification of the HMG box with Gibberella-specific primers GfHMG1 and GfHMG2. Lanes 2 to 16 are amplification products from the same source as in panel A. Lane 1, HMG-box sequence amplified from G. fujikuroi A-00999 by PCR with the NcHMG1 and NcHMG2 primers.