Fig. 1: Virus detection in Neurospora spp. and experimental introduction of heterologous viruses into the Neurospora crassa strain.

Agarose gel electrophoresis of dsRNA fractions obtained from N. intermedia (a), N. crassa (b), and N. discreta (c). After electrophoresis, dsRNA extracted from isolates of Neurospora spp. shown on the top of each gel was stained with GelGreen (Biotium, Inc.). Fully sequenced viruses are Neurospora intermedia fusarivurs 1 (NiFV1), Neurospora crassa fusarivurs 1 (NcFV1), and Neurospora crassa partitivirus 1 (NcPV1). Multiple dsRNA bands were detected in N. discreta isolate FGSC #8549 that is expected to represent the genomes of several RNA viruses (Table 1). The 15 field-collected N. crassa strains were subjected to dsRNA analyses together with a potential virus-free standard strain FGSC #2489 (Supplementary Table 1). The discrete dsRNAs of ~2–3 kbp detectable in N. crassa JW45, JW70, and D23 may be defective RNAs. d Experimental introduction of encapsidated dsRNA viruses into N. crassa via virion transfection. Virions of Rosellinia necatrix partitivirus 2 (RnPV2) and mycoreovirus 1 (MyRV1) were purified from their original host fungi and transfected into protoplasts of the standard strain of N. crassa. DsRNA was isolated from the representative transfectant by RnPV2 and MyRV1 as well as the virus-free standard strain (VF) and electrophoresed in agarose gel. Lane M indicates 1-kb DNA ladder (Thermo Fisher Scientific). e Experimental introduction of a putative capsidless (+)ssRNA virus into N. crassa. Protoplasts of N. intermedia (FGSC #2559) infected by a fusarivirus NiFV1 and the standard N. crassa strain were fused. Each of the experiments shown in panels a–e was independently repeated at least twice.