Growth, Differentiation and Sexuality

Fig. 17.5.A–D Organisation of the pheromone and receptor
genes at the a and B mating type loci of A Ustilago maydis,
B Coprinus cinereus and C Schizophyllum commune. The
receptor genes are designated pra1 and pra 2 in U. maydis,
rcb1, rcb2 and rcb3 in C. cinereus, andbar and bbr in S.
commune. The prefix mfa is used to denote the pheromone
genes of U. maydis, phb in C. cinereus, and either bap or
Fig. 17.6. Alternative forms of the mating type locus of
Cryptococcus neoformans serotype D. Genes and their orientation
are indicated by arrows. Genes encoding mating
pheromonesandreceptorsandelementsoftheMAPKpathway
are shown in bold and homeodomain protein-encoding
Mating Type Genes in Basidiomycetes 363
bbp in S. commune. Different fill motifs indicate different
alleles of the genes in U. maydis or paralogous sets of genes
in C. cinereus and S. commune. Adouble line separating
the Bα and Bβ loci of S. commune indicates a region of
unusual DNA sequence that suppresses recombination. D
Consequence of a compatible combination of pheromones
and receptors during mating
genes as shaded. Numbers are used to indicate other genes
present at MAT; allgenesarepresentinbothlocibutthe
alleles vary in sequence, order and orientation (based on
Hull et al. 2005)