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Published on January 4, 2008; 10.1104/pp.107.110742

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Received October 10, 2007
Accepted December 22, 2007

Cooperative Ethylene and Jasmonic Acid Signaling Regulates Selenite Resistance in Arabidopsis

Masanori Tamaoki *, John L. Freeman , and Elizabeth A. H. Pilon-Smits

Biology Department, Colorado State University, Fort Collins, CO 80523, USA; Environmental Biology Division, National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan

* Corresponding author; email: mtamaoki{at}nies.go.jp.

Selenium (Se) is an essential element for many organisms, but excess Se is toxic. To better understand plant Se toxicity and resistance mechanisms, we compared the physiological and molecular responses of two Arabidopsis accessions, Col-0 and Ws-2, to selenite treatment. Measurement of root length Se tolerance index demonstrated a clear difference between selenite-resistant Col-0 and selenite-sensitive Ws-2. Macroarray analysis showed more pronounced selenite-induced increases in mRNA levels of ethylene or jasmonic acid (JA) biosynthesis and -inducible genes in Col-0 than in Ws-2. Indeed, Col-0 exhibited higher levels of ethylene and JA. The selenite-sensitive phenotype of Ws-2 was attenuated by treatment with ethylene precursor or MeJA. Conversely, the selenite resistance of Col-0 was reduced in mutants impaired in ethylene- or JA-biosynthesis or signaling. Genes encoding sulfur (S) transporters and S assimilation enzymes were upregulated by selenite in Col-0 but not Ws-2. Accordingly, Col-0 contained higher levels of total S and Se and of non-protein thiols than Ws-2. Glutathione redox status was reduced by selenite in Ws-2 but not in Col-0. Furthermore, the generation of reactive oxygen species (ROS) by selenite was higher in Col-0 than in Ws-2. Together these results indicate that JA and ethylene play important roles in Se resistance in Arabidopsis. ROS may also have a signaling role, and the resistance mechanism appears to involve enhanced S uptake and reduction.






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