Left. Multiples esposures of a stage IV macrophore taken every 3 min under red light. Bilateral blue
illumination was given for 30 min; the left lamp was then
extinguished and the intensity of the right lamp was doubled. The
first four exposures were taken under bilateral illumination (From
D.S. Denison). Right. Macrophores showing phototropism after
illumination from the right (From .T. Ootaki). The macrophore is very
sensitive to blue light, with a threshold close to that of the human
eye. It manages an wide range of sensitivity by using two different
photosystems optimized to operate a different light intensities.
Several mutants have been isolated on the basis of their deffective
phototropism (mad mutants), and some of them have been shown to be
affected in the other photoresponses of Phycomyces:
photophorogenesis and photocarotenogenesis. The gene products required
for this and other photoresponses in Phycomyces are
grouped in a phototransduction
pathway. The mad genes have been
maped and they are not linked in the Phycomyces genetic map. A
recent paper on phototropism and other responses of the macrophore is
the following:
Campuzano
V et al. "Blue-light receptor requirement for gravitropism,
autochemotropism and ethylene response in Phycomyces."
Photochem Photobiol 63 (5): 686-694 (May 1996)
Search Medline database for articles about Phycomyces and phototropism
Method for measuring phototropism
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