title: ITN1, a novel gene encoding an ankyrin-repeat protein that affects the ABA-mediated production of reactive oxygen species and is involved in salt-stress tolerance in Arabidopsis thaliana.
abstract: Salt stress and abscisic acid (ABA) induce accumulation of reactive oxygen species (ROS) in plant cells. ROS not only act as second messengers for the activation of salt-stress responses, but also have deleterious effects on plant growth due to their cytotoxicity. Therefore, the timing and degree of activation of ROS-producing or ROS-scavenging enzymes must be tightly regulated under salt-stress conditions. We identified a novel locus of Arabidopsis, designated itn1 (increased tolerance to NaCl1), whose disruption leads to increased salt-stress tolerance in vegetative tissues. ITN1 encodes a transmembrane protein with an ankyrin-repeat motif that has been implicated in diverse cellular processes such as signal transduction. Comparative microarray analysis between wild-type and the itn1 mutant revealed that induction of genes encoding the ROS-producing NADPH oxidases (RBOHC and RBOHD) under salt-stress conditions was suppressed in the mutant. This suppression was accompanied by a corresponding reduction in ROS accumulation. The ABA-induced expression of RBOHC and RBOHD was also suppressed in the mutant, as was the case for RD29A, an ABA-inducible marker gene. However, the ABA-induced expression of another marker gene, RD22, was not impaired in the mutant. These results suggest that the itn1 mutation partially impairs ABA signaling pathways, possibly leading to the reduction in ROS accumulation under salt-stress conditions. We discuss the possible mechanisms underlying the salt-tolerant phenotype of the itn1 mutant.
authors.affiliation: Department of Biological Sciences, Faculty of Sciences, Kyushu University, Fukuoka, 812-8581 Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Matsuda
authors.forename: Koh
authors.initials: K
authors.lastname: Iba
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017089:Ankyrin Repeat; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018389:Codon, Nonsense / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010957:Plasmids; D018749:RNA, Plant / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D018389:Codon, Nonsense; D010937:Plant Growth Regulators; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D049452:Green Fluorescent Proteins; D012965:Sodium Chloride; D000040:Abscisic Acid; D019255:NADPH Oxidases