title: NADPH-dependent thioredoxin reductase C plays a role in nonhost disease resistance against Pseudomonas syringae pathogens by regulating chloroplast-generated reactive oxygen species.
abstract: Chloroplasts are cytoplasmic organelles for photosynthesis in eukaryotic cells. In addition, recent studies have shown that chloroplasts have a critical role in plant innate immunity against invading pathogens. Hydrogen peroxide is a toxic by-product from photosynthesis, which also functions as a signaling compound in plant innate immunity. Therefore, it is important to regulate the level of hydrogen peroxide in response to pathogens. Chloroplasts maintain components of the redox detoxification system including enzymes such as 2-Cys peroxiredoxins (2-Cys Prxs), and NADPH-dependent thioredoxin reductase C (NTRC). However, the significance of 2-Cys Prxs and NTRC in the molecular basis of nonhost disease resistance is largely unknown. We evaluated the roles of Prxs and NTRC using knock-out mutants of Arabidopsis in response to nonhost Pseudomonas syringae pathogens. Plants lacking functional NTRC showed localized cell death (LCD) accompanied by the elevated accumulation of hydrogen peroxide in response to nonhost pathogens. Interestingly, the Arabidopsis ntrc mutant showed enhanced bacterial growth and disease susceptibility of nonhost pathogens. Furthermore, the expression profiles of the salicylic acid (SA) and jasmonic acid (JA)-mediated signaling pathways and phytohormone analyses including SA and JA revealed that the Arabidopsis ntrc mutant shows elevated JA-mediated signaling pathways in response to nonhost pathogen. These results suggest the critical role of NTRC in plant innate immunity against nonhost P. syringae pathogens.
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan; Plant Biology, The Samuel Roberts Noble Foundation, Ardmore, OK, USA.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishiga
authors.affiliation: Plant Biology, The Samuel Roberts Noble Foundation , Ardmore, OK , USA.
authors.forename: Takako
authors.initials: T
authors.lastname: Ishiga
authors.affiliation: Institute of Plant Science and Resources, Okayama University , Kurashiki , Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ikeda
authors.affiliation: Institute of Plant Science and Resources, Okayama University , Kurashiki , Japan.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Matsuura
authors.affiliation: Plant Biology, The Samuel Roberts Noble Foundation , Ardmore, OK , USA.
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
keywords: Arabidopsis; Chloroplast; Localized cell death; NTRC; Nonhost disease resistance; Pseudomonas syringae; Reactive oxygen species