Removal by Yeast Extract of Inhibition by Diethylstilbestrol of Growth and Light-Induced Phase-Shifting in Neurospora crassa

Effects of yeast extract on the inhibitory effects of diethylstilbestrol (DES) were examined in Neurospora crassa The inhibition by DES of mycelial growth and lightinduced phase-shifting of the conidiation rhythm was overcome by the concomitant addition of yeast extract in which the active agents were substances of low molecular weight. However, shifting of the phase of the conidiation rhythm by DES was not affected by addition of the yeast extract. These results suggest that DES exerts an effect at two different sites, at least, in Neurospora: one site being the system which connects the perception of light to the clock mechanism and is related to mycelial growth; the other site being the system which controls the clock mechanism itself.