Polyamines Are Generally Involved In Disease Resistance

Abstract

Polyamines are small molecules with various physiological functions. We previously showed that polyamines were involved in the hypersensitive response (HR) against tobacco mosaic virus. H₂O₂ derived from polyamine degradation by polyamine oxidase triggered off hypersensitive cell death. However, it remains to be determined whether polyamines are generally involved in the HR of other plants, and contribute to nonhost HR, a non specific resistance throughout plants. Polyamine accumulation in apoplasts was observed during the HR in Arabidopsis and rice, indicating that not only dicots but also monocots employ polyamines for the HR. Upon nonhost pathogen infection to tobacco plants, polyamine-related genes were activated, resulting in polyamine accumulation in apoplasts. H₂O₂ and hypersensitive cell death occurred at infected sites. VIGS-mediated PAO-silenced plants showed a decrease of H₂O₂ generation and incomplete hypersensitive cell death. These results suggest that polyamine-derived H₂O₂ contributes to nonhost HR, and that polyamines are commonly utilized for disease resistance.