Ethylene Biosynthesis-Inducing Endoxylanase Is Translocated through the Xylem of Nicotiana tabacum cv Xanthi Plants

Ethylene biosynthesis-inducing xylanase (EIX) from the fungus Trichoderma viride elicits enhanced ethylene production and tissue necrosis in whole tobacco (Nicotiana tabacum cv Xanthi) plants at sites far removed from the point of EIX application when applied through a cut petiole. Symptoms develop in a specific pattern, which appears to be determined by the interconnections of the tobacco xylem. Based on results of tissue printing experiments, EIX enters the xylem of the stem from the point of application and rapidly moves up and down the stem, resulting in localized foliar symptoms on the treated side of the plant above and below the point of EIX application. The observation that a fungal protein that elicits plant defense responses can be translocated through the xylem suggests that plants respond to pathogen-derived extracellular proteins in tissues distant from the invading pathogen.