Cooperative Ethylene and Jasmonic Acid Signaling Regulates Selenite Resistance in Arabidopsis    

Abstract

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 (Arabidopsis thaliana) accessions, Columbia (Col)-0 and Wassilewskija (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 methyl jasmonate (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 up-regulated by selenite in Col-0 but not Ws-2. Accordingly, Col-0 contained higher levels of total S and Se and of nonprotein 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 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. Reactive oxygen species may also have a signaling role, and the resistance mechanism appears to involve enhanced S uptake and reduction.

The effects of selenium and other micronutrients on the antioxidant activities and yield of corn (Zea mays L.) under drought stress

“…Se can also affect plant growth through influencing the production of jasmonic acid and the stress hormone ethylene and the proteins, which affect the plant resistance versus pathogens and sulfate/selenite production (Tamaoki et al 2008). GPX contains Se in its structure, which can influence the enzyme activity.…”

New insights into the roles of ethylene and jasmonic acid in the acquisition of selenium resistance in plants

“…Furthermore, selenite treatment led to enhance ethylene generation and JA accumulation, particularly in the selenite-resistant ecotype Col-0. 1 Together, these results suggest that Se treatment triggers ethylene and JA production and responses. The importance of ethylene and JA for Se resistance in plants was further investigated using Arabidopsis mutants deficient in an aspect of ethylene-or JA-biosynthesis or signaling (acs6, ein2 and jar1).…”

“…These mutants showed less resistance to selenite and selenate than wildtype plants. 1,7 Conversely, treatment of MeJA or 1-aminocyclopropane-1-carboxylic acid (ACC; precursor of ethylene) enhanced selenite resistance in a Se-sensitive Arabidopsis ecotype, Ws-2. 1 These results further suggest that ethylene and JA are important for Se resistance in plants.…”

“…1 This plant hormone is a major phenylpropanoid compound whose biosynthesis is triggered by various biotic and abiotic stresses. 11,12 Although SA levels were enhanced by selenite, our results suggest that SA production inhibits acquisition of plant Se resistance rather than enhancing it, like JA and ethylene.…”

“…Induction of many of these same ethylene and/or JA responsive genes was also observed in selenite-treated plants. 1 These include the gene encoding allene oxide synthase (AOS), a key enzyme in JA biosynthesis, 8 and known to be induced by MeJA. 9 Another selenite-induced gene was PDF1.2 which encodes a plant defensin that requires concomitant triggering of the ethylene and JA pathway for its induction.…”