Inoculations of GUS-RNAi tobacco lines with GUS expressing Fusarium verticillioides. (A) Mycelium cells exhibiting stable and high gus gene expression were used for the inoculation of plant leaves. (B) GUS assay carried out with GUS-RNAi tobacco leaves inoculated with the GUS+ fungus. Fungal mycelia interacting with the re-transformed plant did not show GUS expression; only a few germinating spores presented GUS expression. (C) GUS assay with non-transformed tobacco leaves inoculated with GUS+ fungus. Fungal mycelia showed high GUS expression level. (D, E) After GUS assay, leaf surfaces (presented in B and C) were observed under a scanning electron microscope in order to observe spores germinating and penetrating into stomata.