title: Light-dependent expression of flg22-induced defense genes in Arabidopsis.
abstract: Chloroplasts have been reported to generate retrograde immune signals that activate defense gene expression in the nucleus. However, the roles of light and photosynthesis in plant immunity remain largely elusive. In this study, we evaluated the effects of light on the expression of defense genes induced by flg22, a peptide derived from bacterial flagellins which acts as a potent elicitor in plants. Whole-transcriptome analysis of flg22-treated Arabidopsis thaliana seedlings under light and dark conditions for 30 min revealed that a number of (30%) genes strongly induced by flg22 (>4.0) require light for their rapid expression, whereas flg22-repressed genes include a significant number of genes that are down-regulated by light. Furthermore, light is responsible for the flg22-induced accumulation of salicylic acid (SA), indicating that light is indispensable for basal defense responses in plants. To elucidate the role of photosynthesis in defense, we further examined flg22-induced defense gene expression in the presence of specific inhibitors of photosynthetic electron transport: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and 2,5-dibromo-3-methyl-6-isopropyl-benzoquinone (DBMIB). Light-dependent expression of defense genes was largely suppressed by DBMIB, but only partially suppressed by DCMU. These findings suggest that photosynthetic electron flow plays a role in controlling the light-dependent expression of flg22-inducible defense genes.
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sano
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Mayu
authors.initials: M
authors.lastname: Aoyama
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Nakai
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Shimotani
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Yamasaki
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Masa H
authors.initials: MH
authors.lastname: Sato
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tojo
authors.affiliation: Biology Department, Faculty of Science, Tadulako University Palu, Indonesia.
authors.forename: I Nengah
authors.initials: IN
authors.lastname: Suwastika
authors.affiliation: Department of Health and Nutrition, Gifu Women's University Gifu, Japan.
authors.forename: Hironari
authors.initials: H
authors.lastname: Nomura
authors.affiliation: Graduate School of Life and Environmental Sciences, Kyoto Prefectural University Kyoto, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shiina
keywords: CAS; DBMIB; DCMU; defense gene; flg22; photosynthesis; retrograde signaling; salicylic acid