PHOTOSTIMULATION OF CONIDIATION IN MUTANTS OF NEUROSPORA-CRASSA

Various mutants of Neurospora crassa were screened for light-stimulated conidiation which is a blue light effect and, at least in strain albino-band, is mediated by the flavoprotein nitrate reductase (NR). NR- mutants showed practically no photoconidiation under standard conditions. However, in fusion products of nit-1 (diaphorase activity present, terminal activity missing) plus nit-3 (terminal activity present, diaphorase activity missing), NR activities and photoconidiation were partially restored. Mutants with altered light sensitivities, such as white collar WC-1 and light-insensitive lis-2 and lis-3, had normal NR activities and their conidiation was promoted by light, whereas WC-2 and lis-1 responded only slightly. These two mutants showed low NR activities especially when grown on solid medium which might be the cause of their blindness. Experiments with NR- mutants indicated that nitrite reductase might also act as a blue light photoreceptor.