title: Na⁺/H⁺ exchanger 1 participates in tobacco disease defence against Phytophthora parasitica var. nicotianae by affecting vacuolar pH and priming the antioxidative system.
abstract: Despite the importance of NHX1 (Na(+)/H(+) exchanger 1) in plant salt tolerance, little is known about its other functions. In this study, intriguingly, it was found that NHX1 participated in plant disease defence against Phytophthora parasitica var. nicotianae (Ppn) in Nicotiana benthamiana. NbNHX1 was originally isolated from N. benthamiana, and characterized. The subcellular localization of NbNHX1 with its C-terminus fused with green fluorescent protein indicated that NbNHX1 localized primarily to the tonoplast. Tobacco rattle virus-induced NbNHX1 silencing led to reduced H(+) efflux from the vacuole to cytoplasts, and decreased Ppn resistance in N. benthamiana. After attack by Ppn, NbNHX1-silenced plants exhibited impaired ability to scavenge reactive oxidative species (ROS) induced by the pathogen. Pea early browning virus-mediated ectopic expression of SeNHX1 (from Salicornia europaea) or AtNHX1 (from Arabidopsis thaliana) both conferred enhanced Ppn resistance to N. benthamiana, with a lower H2O2 concentration after Ppn inoculation. Further investigation of the role of NHX1 demonstrated that transient overexpression of NbNHX1 improved the vacuolar pH and cellular ROS level in N. benthamiana, which was coupled with an enlarged NAD(P) (H) pool and higher expression of ROS-responsive genes. In contrast, NbNHX1 silencing led to a lower pH in the vacuole and a lower cellular ROS level in N. benthamiana, which was coupled with a decreased NAD(P) (H) pool and decreased expression of ROS-responsive genes. These results suggest that NHX1 is involved in plant disease defence; and regulation of vacuolar pH by NHX1, affecting the cellular oxidation state, primes the antioxidative system which is associated with Ppn resistance in tobacco.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Xianyang
authors.initials: X
authors.lastname: Chen
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Hexigeduleng
authors.initials: H
authors.lastname: Bao
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Jie
authors.initials: J
authors.lastname: Guo
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Weitao
authors.initials: W
authors.lastname: Jia
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Fang
authors.initials: F
authors.lastname: Tai
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Nie
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Ping
authors.initials: P
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Feng
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
authors.forename: Sulian
authors.initials: S
authors.lastname: Lv
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China yxli@ibcas.ac.cn.
authors.forename: Yinxin
authors.initials: Y
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D000975:Antioxidants / Q000378:metabolism; D060467:Disease Resistance; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000502:physiology*; D010935:Plant Diseases / Q000276:immunology*; D018515:Plant Leaves; D016415:Sequence Alignment; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000276:immunology*; D014617:Vacuoles / Q000378:metabolism
chemical_list: D000975:Antioxidants; D017923:Sodium-Hydrogen Exchangers; D006861:Hydrogen Peroxide
keywords: Cellular redox homeostasis; NAD(P) (H) pool; NHX1; disease resistance; tobacco; vacuolar H+ flux and pH.