title: Salicylic acid accumulation under O3 exposure is regulated by ethylene in tobacco plants.
abstract: Ozone (O3), a major photochemical oxidant, induces leaf injury concomitant with salicylic acid (SA) synthesis. In pathogen-infected leaves, SA is synthesized via two pathways, involving phenylalanine or isochorismate. SA biosynthesis under O3 fumigation is not well understood. When we applied 14C-labeled benzoic acid (a precursor of SA in the pathway via phenylalanine) to O3-exposed tobacco leaves, it was effectively metabolized to SA. However, the activity and mRNA level of isochorismate synthase (ICS) were not increased. In contrast, ICS activity was increased in O3-exposed Arabidopsis thaliana L. These results suggest that SA is synthesized via benzoic acid from phenylalanine in O3-exposed tobacco leaves but via isochorismate in Arabidopsis. Ethylene is a plant hormone that promotes leaf damage in O3-exposed plants. During O3 exposure, transgenic plants with a phenotype of reduced O3-induced ethylene production accumulated less SA than did wild-type plants. O3 increased the activity of phenylalanine ammonia-lyase (PAL) and the transcript levels of the chorismate mutase (CM) and PAL genes in wild-type tobacco, but their induction was suppressed in the transgenic plants. These results indicate that ethylene promotes SA accumulation by regulating the expression of the CM and PAL genes in O3-exposed tobacco.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8572 Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ogawa
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Nakajima
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Sano
authors.forename: Masanori
authors.initials: M
authors.lastname: Tamaoki
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Aono
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kubo
authors.forename: Machi
authors.initials: M
authors.lastname: Kanna
authors.forename: Motohide
authors.initials: M
authors.lastname: Ioki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kamada
authors.forename: Hikaru
authors.initials: H
authors.lastname: Saji
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D002826:Chorismate Mutase / Q000235:genetics; D005030:Ethylenes / Q000096:biosynthesis / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D019751:Intramolecular Transferases / Q000737:chemistry / Q000235:genetics; D017136:Ion Transport; D008969:Molecular Sequence Data; D010126:Ozone / Q000494:pharmacology*; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism*; D016415:Sequence Alignment; D014026:Nicotiana / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D005030:Ethylenes; D012333:RNA, Messenger; D018749:RNA, Plant; D010126:Ozone; C036216:ethylene; D010650:Phenylalanine Ammonia-Lyase; D019751:Intramolecular Transferases; C058486:isochorismate synthase; D002826:Chorismate Mutase; D020156:Salicylic Acid