Indications for the Occurrence of Nitric Oxide Synthases in Fungi and Plants and the Involvement in Photoconidiation of Neurospora crassa*

Indications for the occurrence of nitric oxide synthases in Dictyostelium, Neurospora, Phycomyces and the leguminous plant Mucuna hassjoo as well as a physiological role of nitric oxide in Neurospora crassa are demonstrated. An exogenous nitic oxide donor, sodium nitroprusside, inhibited light-stimulated conidiation in N. crassa. Specific inhibitors of nitric oxide synthase, like the arginine derivatives NG -nitro-L-arginine (L-NA) and NG-nitro-L-arginine-methyl ester (L-NAME), enhanced conidiation in darkness nad in the light, whereas the stereoisomer D-NAME was inactive. This communication reports to our knowledge the first time the presence of enzymatic activity of nitric oxide synthase in fungi and a higher plant and an effect of nitric oxide in fungal photo-physiology.