Temperature-shift analysis of conidial development in Aspergillus nidulans

Light is required for conidiation in Aspergillus nidulans.

“…The time of conidiophore vesicle appearance and the time of conidial maturation were assayed from noninduced single colonies, as described by Axelrod (1972) and Yager et al {1982). n = 3 for the submerged growth rate determination; and n = 5 for the radial growth rate determination ___ SD.…”

“…Both genes show a low level of m R N A accumulation in the light, but a sharp increase in transcription is observed in the dark commencing at -8 hr after induction for CAN65 and between 10 and 12 hr after induction for CAN77. Because certain conidiation-specific genes function both in asexual and sexual development (Yager et al 1982;Jurgenson and Champe 1990) and the initiation of sexual development is precocious in dark-grown veA + colonies, occurring -1 5 hr earlier than in light-grown colonies (J.L. Mooney and L.N.…”

“…The existence of these functions is inferred from the isolation and genetic analysis of aconidial mutants, which are blocked in the formation of developmental structures (Martinelli and Clutterbuck 1971;Yager et al 1982) and from the molecular analysis of developmental gene regulation (Timberlake 1980). These early functions are followed by late conidiationspecific gene functions, which are involved in the direct formation and regulation of differentiated structures.…”

“…Using the growth conditions described, cube-root growth was observed and submerged growth rates were presented as milligrams dry weight l/a/hr {Emerson 1950; Marshall and Alexander 1960). Radial colonial growth rates, which obey a linear growth relationship, were determined as described in Yager et al (1982).…”

The Aspergillus nidulans fluG gene is required for production of an extracellular developmental signal and is related to prokaryotic glutamine synthetase I.

“…For wild-type A. nidulans, conidiophore develop ment initiates in the center of a colony within -24 hr of spore germination, then spreads rapidly toward the edge of the colony so that young conidiophores appear within 1-2 mm of the colony margin, and mature conidiophores are found toward the colony center. Mutations in several distinct genetic loci disrupt programmed initiation of the conidiation pathway, resulting in a fluffy phenotype characterized by the proliferation of undifferentiated aerial hyphae, which give the colony a cotton-like ap pearance (Roper 1958;Dom 1970;Yager et al 1982;Tamame et al 1983;Adams et al 1992). The results presented in this paper demonstrate that the fluffy phe notype resulting from deletion of the fluG [acoD] gene is rescued and normal conidiophores are produced when fluG deletion mutants are grown next to wild-type conidiating A. nidulans strains.…”