Growth, Differentiation and Sexuality

19 The Emergence of Fruiting Bodies in Basidiomycetes
H.A.B. Wösten 1 , J.G.H. Wessels 2
CONTENTS
I. Introduction ......................... 393
II. Development of Emergent Structures ...... 394
A. Formation of a Feeding Submerged
Mycelium......................... 394
B. Formation of Fruiting Bodies
fromtheSubmergedMycelium ........ 394
III. Regulation of Fruiting-Body
Formation ........................... 396
A. EnvironmentalSignals............... 396
B. Mating-Type Genes as Master Regulators 397
C. OtherRegulatoryGenes.............. 398
1.HaploidFruiting ................. 399
2. Regulatory Genes in Establishment
of the Dikaryotic Mycelium
and in Fruiting-Body Formation . . . . . 399
3. Regulatory Genes in Fruiting-Body
Formation but not in Establishment
oftheDikaryoticMycelium ......... 401
D. Nuclear Positioning ................. 401
IV. Proteins Involved in Fruiting ............ 402
A. Hydrophobins ..................... 402
B. SC7 and SC14 . . . . . . . . . . . . . . . . . . . . . . 405
C. Lectins ........................... 405
D. Haemolysins....................... 406
E. OxidativeEnzymes.................. 406
F. Enzymes Involved
inCarbohydrateMetabolism .......... 407
V. Conclusions .......................... 407
References ........................... 408
I. Introduction
Fruiting bodies are adaptations for aerial dissemination
of sexual spores by assimilative
mycelia, which grow within moist substrata.
Most species of the homobasidiomycetes produce
large fruiting bodies, also called basidiocarps,
carpophores or basidiomes (Moore 1998). It is
generally the case that, in these fruiting bodies,
1 Microbiology, Institute of Biomembranes, University of Utrecht,
Padualaan 8, 3584 CH Utrecht, The Netherlands
2 Department of Plant Biology, University of Groningen, Kerklaan
30, 9751 NN Haren, The Netherlands
specialised cells, basidia, are generated in which
genetically different haploid nuclei, derived
from a mating event and coexisting in a common
cytoplasm (a heterokaryon), fuse to form
diploid nuclei. These diploid cells immediately
undergo meiosis to form haploid basidiospores.
In some cases, diploid nuclei are already formed
in the vegetative mycelium, as in Armillaria
species (Ullrich and Anderson 1978; Grillo et al.
2000).
After discharge, the haploid basidiospores can
germinate and generate recombinant homokaryotic
mycelia which, depending on an often
complex system of mating-type genes, can fuse
to produce a new, fertile heterokaryotic mycelium
(see Chap. 17, this volume). Basidiomycete
species behaving according to this scheme are
in the majority and are called heterothallic (i.e.
self-incompatible). From a teleological point
of view, this makes sense because it ensures
that the diploid basidia produce recombinant
meiotic progeny. It is less clear why a minority
of basidiomycetes (about 10%; Whitehouse
1949) is homothallic (i.e. self-compatible).
Mycelia resulting from basidiospores of such
species are capable of directly forming fruiting
bodies. Homothallic forms can arise from heterothallic
forms by various mechanisms (see
Sect. III.B).
This review discusses the regulation of
fruiting-body formation in basidiomycetes and the
role structural proteins and enzymes play in this
process. Related topics, including morphogenesis,
cytology and mathematical modelling, are well
treated in Wells and Wells (1982), Moore et al.
(1985), Wessels (1993a), Chiu and Moore (1996),
Moore (1998), Kües (2000), and Meskauskas et al.
(2004). Fruiting of commercially important species
for mushroom cultivation is treated in Chang and
Hays (1978), Flegg et al. (1985), Wuest et al. (1987),
van Griensven (1988), Kües and Liu (2000) and
Kothe (2001).
The Mycota I
Growth, Differentation and Sexuality
Kües/Fischer (Eds.)
© Springer-Verlag Berlin Heidelberg 2006