| Abstract: | Abstract— In the zygomycete Phycomyces blakesleeanus the morphogenesis of both macrosporangiophores and microsporangiophores is under separate control of different blue-light photoreceptors. Blue light represses microphorogenesis and enhances macrophorogenesis. Both, flavins and pterins are discussed as possible components of these blue-light photoreceptors. 2,4-Diamino-6-hydroxypyrimidine (DAHP) was shown to be an inhibitor of GTP-cyclohydrolase I, the initial enzyme of pteridine biosynthesis, in vitro and in vivo in Phycomyces. When grown on agar plates containing 5 mM of DAHP, Phycomyces shows a 6.0-fold reduction of light-dependent enhancement of macrophorogenesis, and microphorogenesis was 3.1 times less repressed when compared with controls grown without DAHP. This implies a participation of pteridines in blue-light photoreception in both phenomena, with greater influence on macrophorogenesis enhancement than on microphorogenesis repression. |
