Altered Stereostructures of the DNA-Binding Domains of Variant Mating Proteins of Ophiocordyceps sinensis and the Wild Insect-Fungal Complex.

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Citation abstract

The MATα_HMGbox and HMG-box_ROX1-like domains of the MAT1-1-1 and MAT1-2-1 proteins, respectively, play essential roles in DNA binding and the subsequent regulation of gene transcription, controlling Ophiocordyceps sinensis sexual reproduction. Alternative splicing, differential occurrence and transcription of the MAT1-1-1 and MAT1-2-1 genes have been demonstrated in Hirsutella sinensis (GC-biased Genotype #1 of the 17 O. sinensis genotypes), suggesting self-sterility under heterothallic or hybrid outcrossing. In this study, the MATα_HMGbox domains of MAT1-1-1 proteins in wild-type Cordyceps sinensis isolates were shown to cluster into 5 clades in the Bayesian clustering tree and belong to diverse stereostructure morphs under 19 AlphaFold codes. The HMG-box_ROX1-like domains of MAT1-2-1 proteins, on the other hand, were shown to cluster into 2 branched Bayesian clades and belong to stereostructure morphs under 25 AlphaFold codes. Correlation analysis revealed that 1-3 amino acid substitutions in the DNA-binding domains of the mating proteins resulted in altered hydrophobicity and secondary and tertiary structures of the DNA-binding domains of the proteins, especially altered stereostructures of the hydrophobic cores formed by 3 critical α- helices within the functional domains of the proteins. Fungal origin analysis revealed possible heterospecific fungal sources of mating proteins with stereostructure variations in wild-type C. sinensis isolates, suggesting that alterations in DNA binding function and the subsequent regulation of mating-related gene transcription are involved in ensuring the accuracy and genetic diversity of heterothallic and hybrid reproduction of O. sinensis during the lifecycle of the C. sinensis insect-fungal complex.