A chimeric homeodomain protein causes self-compatibility and constitutive sexual development in the mushroom Coprinus cinereus.
The A mating type genes of the mushroom Coprinus cinereus encode two classes of putative transcription factor with distinctive homeodomain motifs (HD1 and HD2). A successful mating brings together different allelic forms of these genes and this triggers part of a developmental sequence required for sexual reproduction. In this report we provide evidence that this developmental programme is promoted by a physical interaction between the two classes of homeodomain protein. Rare dominant mutations conferring self-compatibility map to the A locus and result in constitutive operation of the A-regulated developmental pathway. Our molecular analysis of one of these mutations shows that it has generated a chimeric gene by inframe fusion of an HD2 and an HD1 gene. Fusion has overcome the normal incompatibility between two proteins coded by genes of the same A locus and generated a protein that is sufficient to promote development in the absence of any other active A mating type genes. The fusion protein retains most of the HD2 sequence, but only the C-terminal part of the HD1 protein. It has only the HD2 homeodomain motif as a potential DNA binding domain fused to an essential C-terminal region of the HD1 protein, which in a normal HD1-HD2 protein complex may be the major activation domain.
Kües
U
U
Department of Plant Sciences, University of Oxford, UK.
Göttgens
B
B
Stratmann
R
R
Richardson
W V
WV
O'Shea
S F
SF
Casselton
L A
LA
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003302:Coprinus / Q000166:cytology / Q000235:genetics*; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics*; D015321:Gene Rearrangement; D005800:Genes, Fungal / Q000235:genetics*; D005801:Genes, Homeobox / Q000235:genetics*; D049770:Genes, Mating Type, Fungal; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012098:Reproduction / Q000235:genetics; D017384:Sequence Deletion; D012723:Sex; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics
D005656:Fungal Proteins; C099790:HD1 protein, Coprinus cinereus; C099791:HD2 protein, Coprinus cinereus; D018398:Homeodomain Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors