Introduction to Fungi, Third Edition

HETEROBASIDIOMYCETE YEASTS
663
Fig 24.2 Life cycle of Filobasidiella neoformans. Note that only the a but not the a mating type is able to reproduce by haploid
conidia. Based partly on Kwon-Chung and Bennett (1992) and Kwon-Chung (1998).Open and closed circles represent haploid
nuclei of opposite mating type; diploid nuclei are larger and half-filled. Key events in the life cycle are plasmogamy (P), karyogamy
(K) and meiosis (M).
mating type idiomorph of C. neoformans to the sex
chromosomes of other organisms. This situation
is most unusual for Basidiomycota which typically
have two unlinked mating type loci (e.g.
A and B in Coprinus cinereus or Schizophyllum
commune; see p. 508) encoding a receptor/pheromone
system and a transcription factor.
Another, though structurally different, example
of a sex chromosome may be found in Ustilago
hordei (see p. 637).
Infection and therapy
The available evidence suggests that infection
with C. neoformans is initiated by inhalation, and
that the disease is not spread between humans.
This is probably because the infectious particles
must be very small (