Journal
PLANT JOURNAL
Volume 56, Issue 3, Pages 411-422Publisher
WILEY
DOI: 10.1111/j.1365-313X.2008.03614.x
Keywords
ITN1; salt stress; reactive oxygen species; abscisic acid; ankyrin repeat; Arabidopsis
Categories
Funding
- Core Research for Evolutional Science and Technology
- Japan Science and Technology Agency
- Ministry of Agriculture, Forestry and Fisheries of Japan [IP5005]
- Japan Society for the Promotion of Science [17370019]
- Grants-in-Aid for Scientific Research [17370019] Funding Source: KAKEN
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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.
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