Growth, Differentiation and Sexuality

12 Pheromone Action in the Fungal Groups Chytridiomycota,
and Zygomycota, and in the Oomycota
C. Schimek 1 ,J.Wöstemeyer 1
CONTENTS
I. Introduction ......................... 215
II. Recognition and Development ........... 215
A. Chytridiomycota ................... 215
1.Structures....................... 215
2.ModeofAction................... 217
B. Zygomycota ....................... 218
1.Structures....................... 218
2.Biosynthesis..................... 219
3.ModeofAction................... 220
4.GeneticConsequences............. 222
C. Oomycota......................... 223
1.Structures....................... 223
2.Biosynthesis.....................
3. Mode of Action
224
andCellularConsequences ......... 225
III. Conclusions .......................... 227
References ........................... 228
I. Introduction
Fungi depend on specific intercellular communication
systems for successfully managing sexual interactions.
Small diffusible molecules are required
for partner recognition, which comprises distinction
between the same and foreign species and reliable
recognition between complementary mating
types. These signals need to be sent out at appropriate
stages of development. They need to be sensed,
differentiated from potentially interfering environmental
signals, interpreted, and finally used for initiating
adequate developmental programmes.
II. Recognition and Development
Looking at the chemical principles behind recognitionofsexual
partners reveals asurprisingdiversity
between the major fungal groups. There is no evidence
for a common communication strategy. In
1 Institut für Mikrobiologie, Lehrstuhl für Allgemeine Mikrobiologie
und Mikrobengenetik, Friedrich-Schiller-Universität Jena,
Neugasse 24, 07743 Jena, Germany
the phylogenetically most basal division Chytridiomycota,
at least the model organism Allomyces
arbuscula uses the sesquiterpene sirenin (Fig. 12.1)
as attractant between the sexually complementary
mobile gametes. All Zygomycota analysed seem
to rely on trisporic acid derivates as mediators
of sexual recognition (Figs. 12.2, 12.3; Schimek
et al. 2003), whereas the Dikaryomycota (Ascomycotina,
Basidiomycotina) rely on communication
schemes based on small peptides (see Chaps. 15–
17, this volume). The non-mycotan group Oomycota
makes use of steroid compounds, e.g. the wellcharacterized
compounds oogoniol and antheridiol
(Fig. 12.4) in Achlya spp. In the plant pathogen
Phytophthora sp., a lipid-based compatibility system
provides an additional regulatory level.
The regulatory substances involved in recognition
and control of sexual processes of fungi have
been variously termed “hormones”, indicating
the activity of the substance beyond its producing
cell or tissue, “pheromones”, or “gamones” to
describe substances involved in attraction between
motile gametes. Other terms, e.g. “attractant”,
“morphogen”, and “sex factor”, are also found
in the relevant literature. Throughout this text,
the term “pheromone” will be used to indicate
a chemical acting at a distance on members of the
same, or other species. Where the importance of
a substance as a mediator of specifically a sexual
process is to be stressed, the term “sex pheromone”
is used.
A. Chytridiomycota
1. Structures
The non-parasitic members of the Chytridiomycota
occur mainly in fresh-water habitats or moist
soil. Within the taxon, sexual reactions are carried
outfollowinganumberofdifferentmechanisms,
all of them involving interactions between motile
gametes. In the genus Allomyces, the two types of
The Mycota I
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