title: Melatonin as a signal molecule triggering defense responses against pathogen attack in Arabidopsis and tobacco.
abstract: Melatonin plays pleiotropic roles in both animals and plants. The possible role of melatonin in plant innate immune responses was recently discovered. As an initial study, we employed Arabidopsis to determine whether melatonin is involved in defense against the virulent bacterial pathogen Pseudomonas syringae DC3000. The application of a 10 μM concentration of melatonin on Arabidopsis and tobacco leaves induced various pathogenesis-related (PR) genes, as well as a series of defense genes activated by salicylic acid (SA) and ethylene (ET), two key factors involved in plant defense response, compared to mock-treated leaves. The induction of these defense-related genes in melatonin-treated Arabidopsis matched an increase in resistance against the bacterium by suppressing its multiplication about ten-fold relative to the mock-treated Arabidopsis. Like melatonin, N-acetylserotonin also plays a role in inducing a series of defense genes, although serotonin does not. Furthermore, melatonin-induced PR genes were almost completely or partially suppressed in the npr1, ein2, and mpk6 Arabidopsis mutants, indicative of SA and ET dependency in melatonin-induced plant defense signaling. This suggests that melatonin may be a novel defense signaling molecule in plant-pathogen interactions.
authors.affiliation: Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors.forename: Hyoung Yool
authors.initials: HY
authors.lastname: Lee
authors.forename: Yeong
authors.initials: Y
authors.lastname: Byeon
authors.forename: Kyoungwhan
authors.initials: K
authors.lastname: Back
mesh_terms: D017360:Arabidopsis / Q000382:microbiology*; D001483:Base Sequence; D017931:DNA Primers; D008550:Melatonin / Q000502:physiology*; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014026:Nicotiana / Q000382:microbiology*
chemical_list: D017931:DNA Primers; D008550:Melatonin
keywords: defense system; ethylene signaling; innate immunity; melatonin; pathogen; salicylic acid signaling