Growth, Differentiation and Sexuality

234 L.M. Corrochano and P. Galland
Table. 13.1. Effects of light on fungal development
Organism Phenomenon Threshold Reference
Phycomyces Induction of macrophores
or inhibition of microphores
10 −8 W/m 2 Corrochano and
Cerdá-Olmedo (1990)
10 −4 J/m 2 Corrochano and
Cerdá-Olmedo (1990)
10 −10 mol/m 2 Corrochano et al. (1988)
Inhibition of sexual development 3 ×10 −2 W/m 2 Yamazaki et al. (1996)
Neurospora Induction of protoperithecia 4 J/m 2 Degli-Innocenti et al. (1983)
Circadian clock resetting 10 −5 mol/m 2 Crosthwaite et al. (1995)
Aspergillus Induction of conidiation 135 J/m 2 Mooney and Yager (1990)
8 ×10 −4 mol/m 2 Mooney and Yager (1990)
Trichoderma Induction of conidiation 10−5 mol/m2 Alternaria Inhibition of photoinduced 10
Horwitz et al. (1990)
conidiation
−5 mol/m2 Kumagai (1989)
Paecilomyces Induction of conidiation 1.8 ×10−4 mol/m2 Sánchez-Murillo et al. (2004)
tors, including the presence or absence of light. The
regulation by light of fungal development is generally
referred to as fungal photomorphogenesis
(Fig. 13.1), and can be measured precisely, allowing
one to determine useful parameters such as
thresholds (Fig. 13.2). Blue light is the type most
effective in fungal photomorphogenesis but other
wavelengths can also be important, as shown by
the activation of conidiation by red light in Aspergillus
nidulans (Mooney and Yager 1990), and
by near-ultraviolet light in Alternaria tomato (Kumagai
1989). The effect of blue light is often either
stimulatory or inhibitory of a developmental transition
but the red-light induction of conidiation in
Aspergillus can be inhibited by a subsequent exposure
to far-red light, and the near-UV induction of
conidiation in Alternaria can be inhibited by exposure
to blue light (Kumagai 1989; Mooney and
Fig. 13.1. Photomorphogenesis in Phycomyces. Light inhibition
of microphore initiation and development in Phycomyces.
Microphores are short sporangiophores, 1–2 mm
in length, containing a dark ball on top (sporangia) with
matured spores. The fungus was grown under continuous
light (left) or in the dark (right). Microphores appeared
at the mycelial surface of cultures kept in the dark only.
Photographs by L.M. Corrochano
Yager 1990), suggesting the operation of complex
photoreceptor systems. Fungal photomorphogenesis
has been reviewed extensively (Carlile 1970;
Gressel and Rau 1983; Kumagai 1988; Corrochano
and Cerdá-Olmedo 1991), and the interested reader
is referred to these reviews for details on a variety of
experimental systems described in older literature.
We have therefore decided to summarize the major
discoveries regarding fungal photomorphogenesis
that have been published in the last 10–15 years.
Fig. 13.2. Inhibition of microphorogenesis and stimulation
of macrophorogenesis by blue-light pulses (extracted from
Corrochano and Cerdá-Olmedo 1990). Standard dark cultures,
2 days old, received pulses of blue light of the fluence
given in the abscissa. The number of microphores (top)and
the dry weight of macrophores (bottom) were determined
2 days later, and are shown relative to the values found in
dark cultures