A mating-type factors of Coprinus cinereus have variable numbers of specificity genes encoding two classes of homeodomain proteins

Ursula Kües, Anna M. Tymon, Wendy V.J. Richardson, Georgiana May, Paul T. Gieser, Lorna A. Casselton

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We have identified the seven genes that constitute the A43 mating-type factor of Coprinus cinereus and compare the organisation of A43 with the previously characterised A42 factor. In both, the genes that trigger clamp cell development, the so-called specificity genes, are separated into α and β loci by 7 kb of noncoding sequence and are flanked by homologous genes α-fg and β-fg. The specificity genes are known to encode two classes of dissimilar homeodomain (HD1 and HD2) proteins and have different allelic forms which show little or no cross-hybridisation. By partial sequencing we identified a divergently transcribed HD1 (a1-2) and HD2 (a2-2) gene in the A43 α locus. a2-2 failed to elicit clamp cell development in three different hosts, suggesting that it is non-functional. a1-2 elicited clamp cells in an A42 host that has only an HD2 gene (a2-1) in its α locus, thus demonstrating that the compatible Aα mating interaction is between an HD1 and an HD2 protein. The A43 β locus contains three specificity genes, the divergently transcribed HD1 and HD2 genes b1-2 and b2-2 and a third HD1 gene (d1-1) that was shown by hybridisation and transformation analyses to be functionally equivalent to d1-1 in A42. An untranscribed footprint of a third A42 HD1 gene, c1-1, was detected between the A43 b2-2 and d1-1 genes by Southern hybridisation.

Original languageEnglish (US)
Pages (from-to)45-52
Number of pages8
JournalMGG Molecular & General Genetics
Issue number1
StatePublished - Jan 1 1994



  • A mating-type factor
  • Coprinus cinereus
  • Homeodomain
  • Specificity genes

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