Description of the Nicotiana benthamiana-Cercospora nicotianae pathosystem.

Nicotiana benthamiana is a valuable model organism in plant biology research. This report describes its extended applicability in the field of molecular plant pathology by introducing a nonbiotrophic fungal pathogen Cercospora nicotianae that can be conveniently used under laboratory conditions, consistently induces a necrotic leaf spot disease on Nicotiana benthamiana, and is specialized on solanaceous plants. Our inoculation studies showed that C. nicotianae more effectively colonizes N. benthamiana than its conventional host, N. tabacum. The functions of two critical regulators of host immunity, coronatine-insensitive 1 (COI1) and ethylene-insensitive 2 (EIN2), were studied in N. benthamiana using Tobacco rattle virus-based virus-induced gene silencing (VIGS). Perturbation of jasmonic acid or ethylene signaling by VIGS of either COI1 or EIN2, respectively, resulted in markedly increased Cercospora leaf spot symptoms on N. benthamiana plants. These results suggest that the N. benthamiana-C. nicotianae host-pathogen interaction is a prospective but hitherto unutilized pathosystem for studying gene functions in diseased plants.