Figure 4.
Enhanced disease resistance of transgenic tobacco plants constitutively expressing SCaM-4 or SCaM-5. (A) Disease responses to the virulent fungal pathogen, P. parasitica var. nicotianae. At 7 days after inoculation, plants were examined for disease symptoms. Representative results of wild type (WT), transgenic plants expressing SCaM-4 (S4TG) or SCaM-5 (S5TG) are shown. (B and C) Fluorescence micrographs of leaves infected with the virulent P. parasitica var. nicotianae. Infected leaves were cleared, stained with aniline blue, and examined under an UV-light epifluorescence microscope. In leaves of the wild-type plants (B) the spreading of fungal hyphae is evident, but leaves of the transgenic plants (C) show the accumulation of UV-excitable fluorescent material in the cells surrounding the fungal penetration sites without appreciable growth of fungal hyphae. (Scale bars represent 100 μm.) (D) In planta bacterial growth. Pst was inoculated into leaves of mature wild-type (WT) and transgenic SCaM-4 (S4TG) and SCaM-5 (S5TG) plants at 105 cfu/ml, and in planta bacterial growth was monitored over 5 days. Data points represent means of two determinations from five independent lines. (E) Elevated resistance of SCaM-4 and SCaM-5 transgenic plants to the avirulent pathogen TMV. The second or third fully expanded young leaves from the uppermost part of plants were inoculated with TMV by gently rubbing leaves with carborundum and 2 μg/leaf TMV, and the development of HR lesions were monitored over 5 days. Data shown are the numbers of HR lesions formed in these plants. In all of these pathogen tests, control transgenic plants transformed with an empty vector showed results essentially similar to those of wild-type plants (data not shown).