Mutations and Differential Transcription of Mating-Type and Pheromone Receptor Genes in and the Natural Insect-Fungi Complex.

Sexual reproduction in ascomycetes is controlled by the mating-type (MAT) locus. (Pseudo)homothallic reproduction has been hypothesized on the basis of genetic data from (Genotype #1 of ). However, the differential occurrence and differential transcription of mating-type genes in the and idiomorphs were found in the genome and transcriptome assemblies of , and the introns of the MAT1-2-1 transcript were alternatively spliced with an unspliced intron I that contains stop codons. These findings reveal that reproduction is controlled at the genetic, transcriptional, and coupled transcriptional-translational levels. This study revealed that mutant mating proteins could potentially have various secondary structures. Differential occurrence and transcription of the a-/α-pheromone receptor genes were also found in . The data were inconsistent with self-fertilization under (pseudo)homothallism but suggest the self-sterility of and the requirement of mating partners to achieve sexual outcrossing under heterothallism or hybridization. Although consistent occurrence and transcription of the mating-type genes of both the and idiomorphs have been reported in natural and cultivated insect-fungi complexes, the mutant MAT1-1-1 and α-pheromone receptor transcripts in natural result in N-terminal or middle-truncated proteins with significantly altered overall hydrophobicity and secondary structures of the proteins, suggesting heterogeneous fungal source(s) of the proteins and hybridization reproduction because of the co-occurrence of multiple genomically independent genotypes of and >90 fungal species in natural .