Light-dependent carotenoid synthesis : X. Lag-phase after a second illumination period in Fusarium aquaeductuum and Neurospora crassa.

In dark grown mycelia of the fungi Fusarium aquaeductuum Lagh. and Neurospora crassa the kinetics of carotenoid accumulation after brief illuminations were investigated. Following a second illumination period photoinduced carotenoid biosynthesis started also only after a lag-phase. Such a "secondary" lag-phase not only appeared when the pigment accumulation induced by the first light treatment had been completed, but also when the second illumination was given during the period of rapid carotenoid synthesis induced by the first illumination. The length of the lag-phase, the intensity of the subsequent pigment accumulation as well as the gradual inhibition by cycloheximide is identical after the first and the second illumination. From these results we conclude that in the pgotoregulation of carotenogenesis in fungi by blue light, a second light treatment of preilluminated mycelia gives rise to a renewed induction of the whole sequence of dark reactions.