A-mating-type gene expression can drive clamp formation in the bipolar mushroom Pholiota microspora (Pholiota nameko).
In the bipolar basidiomycete Pholiota microspora, a pair of homeodomain protein genes located at the A-mating-type locus regulates mating compatibility. In the present study, we used a DNA-mediated transformation system in P. microspora to investigate the homeodomain proteins that control the clamp formation. When a single homeodomain protein gene (A3-hox1 or A3-hox2) from the A3 monokaryon strain was transformed into the A4 monokaryon strain, the transformants produced many pseudoclamps but very few clamps. When two homeodomain protein genes (A3-hox1 and A3-hox2) were transformed either separately or together into the A4 monokaryon, the ratio of clamps to the clamplike cells in the transformants was significantly increased to ca. 50%. We therefore concluded that the gene dosage of homeodomain protein genes is important for clamp formation. When the sip promoter was connected to the coding region of A3-hox1 and A3-hox2 and the fused fragments were introduced into NGW19-6 (A4), the transformants achieved more than 85% clamp formation and exhibited two nuclei per cell, similar to the dikaryon (NGW12-163 x NGW19-6). The results of real-time reverse transcription-PCR confirmed that sip promoter activity is greater than that of the native promoter of homeodomain protein genes in P. microspora. Thus, we concluded that nearly 100% clamp formation requires high expression levels of homeodomain protein genes and that altered expression of the A-mating-type genes alone is sufficient to drive true clamp formation.
Yi
Ruirong
R
Faculty of Agriculture, Tottori University, 4-101 Koyama-cho Minami, Tottori 680-8553, Japan.
Mukaiyama
Hiroyuki
H
Tachikawa
Takashi
T
Shimomura
Norihiro
N
Aimi
Tadanori
T
D002467:Cell Nucleus / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D049770:Genes, Mating Type, Fungal; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D055368:Pholiota / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D020161:Physical Chromosome Mapping; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D014158:Transcription, Genetic; D014170:Transformation, Genetic; D020798:Two-Hybrid System Techniques
D005656:Fungal Proteins; D018398:Homeodomain Proteins; D007211:Indoles; C007293:DAPI
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