Growth, Differentiation and Sexuality

sibly due to displacement of the hydrophilic hydroxyl
group of the ring to a region which needs
to be hydrophobic in its interaction with the hypothetical
receptor (Pommerville et al. 1988).
Pheromones 217
2. Mode of Action
Fig. 12.3. A Simplified schematic
representation of the cooperative
biosynthesis of trisporic acid. The
open arrows indicate exchange of
metabolites between the mating
partners. Only the compatible
partner is able to convert the
mating type-specific precursors
into trisporic acid. The two mating
types are indicated by (+) and (−).
B, C Sexual differentiation stages
in Mucor mucedo. B Zygophores
produced by M. mucedo (−) as
reaction to stimulation by either
a compatible mating partner or
purified trisporoids. Bar = 120 μm.
C Upon contact between the
mating types, progametangia
have developed from the original
zygophores. The faint line in the
upper progametangium (arrowhead)
indicates the formation of
a septum delimiting the future
gametangium. Bar = 40 μm
At least under experimental conditions, the mutual
and specific attraction system of the gametes
Fig. 12.4. Biosynthesis pathway
of the steroid sex pheromones
of Achlya spp., derived from the
common precursor fucosterol. Antheridiol
is produced by females via
independently occurring modifications
at the ring system and the side
chain. 24(28)-dehydro-oogoniol-1
represents a number of active oogoniols
produced by male strains.
The unesterified oogoniol and its
24(28)-dehydro-derivate are modified
by three different substituents
at C3: oogoniol-1 (CH3)2CHCO,
oogoniol-2 (CH3)CH2CO, and
oogoniol-3 CH3CO. In the males,
biosynthesis takes place in a more
strictly observed sequence of conversion
steps. Ring modifications
must be finished before the final
modifications at the side chain may
take place