Overexpression of AtCpNifS Enhances Selenium Tolerance and Accumulation in Arabidopsis

Hoewyk, Douglas Van; Garifullina, Gulnara F.; Ackley, Ashley R.; Abdel‐Ghany, Salah E.; Marcus, Matthew A.; Fakra, Sirine C.; Ishiyama, Keiki; Inoue, Eri; Pilon, Marinus; Takahashi, Hideki; Pilon-Smits, Elizabeth A. H.

doi:10.1104/pp.105.068684

Cited by 124 publications

(92 citation statements)

References 42 publications

(52 reference statements)

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“…Incidentally, it is interesting that this secondary accumulator, S. albescens, accumulated such a large fraction of Se in organic form. Other secondary accumulators and nonaccumulators were reported to accumulate mainly selenate when supplied with selenate, with a minor fraction of organic Se with a XANES spectrum similar to SeMet (de Souza et al, 1998;Van Hoewyk et al, 2005). These results, however, may be artifactual and completely due to the short time after selenate treatment before these plants were harvested.…”

Section: Discussioncontrasting

confidence: 41%

“…Light intensity-dependent electron transport rate was measured after 16 weeks of growth from six plants per treatment using the method described by Abdel-Ghany et al (2005). Relative electron transport rate was calculated from the product of FPSII (for electron flux through PSII) and light intensity (mmol m 22 s 21 ).…”

Section: Chlorophyll Fluorescence Measurementsmentioning

confidence: 99%

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Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata

Freeman

Tamaoki²,

Stushnoff³

et al. 2010

Plant Physiol.

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The molecular mechanisms responsible for selenium (Se) tolerance and hyperaccumulation were studied in the Se hyperaccumulator Stanleya pinnata (Brassicaceae) by comparing it with the related secondary Se accumulator Stanleya albescens using a combination of physiological, structural, genomic, and biochemical approaches. S. pinnata accumulated 3.6-fold more Se and was tolerant to 20 mM selenate, while S. albescens suffered reduced growth, chlorosis and necrosis, impaired photosynthesis, and high levels of reactive oxygen species. Levels of ascorbic acid, glutathione, total sulfur, and nonprotein thiols were higher in S. pinnata, suggesting that Se tolerance may in part be due to increased antioxidants and up-regulated sulfur assimilation. S. pinnata had higher selenocysteine methyltransferase protein levels and, judged from liquid chromatography-mass spectrometry, mainly accumulated the free amino acid methylselenocysteine, while S. albescens accumulated mainly the free amino acid selenocystathionine. S. albescens leaf x-ray absorption near-edge structure scans mainly detected a carbon-Se-carbon compound (presumably selenocystathionine) in addition to some selenocysteine and selenate. Thus, S. albescens may accumulate more toxic forms of Se in its leaves than S. pinnata. The species also showed different leaf Se sequestration patterns: while S. albescens showed a diffuse pattern, S. pinnata sequestered Se in localized epidermal cell clusters along leaf margins and tips, concentrated inside of epidermal cells. Transcript analyses of S. pinnata showed a constitutively higher expression of genes involved in sulfur assimilation, antioxidant activities, defense, and response to (methyl)jasmonic acid, salicylic acid, or ethylene. The levels of some of these hormones were constitutively elevated in S. pinnata compared with S. albescens, and leaf Se accumulation was slightly enhanced in both species when these hormones were supplied. Thus, defense-related phytohormones may play an important signaling role in the Se hyperaccumulation of S. pinnata, perhaps by constitutively up-regulating sulfur/Se assimilation followed by methylation of selenocysteine and the targeted sequestration of methylselenocysteine.

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Section: Discussioncontrasting

confidence: 41%

Section: Chlorophyll Fluorescence Measurementsmentioning

confidence: 99%

Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata

Freeman

Tamaoki²,

Stushnoff³

et al. 2010

Plant Physiol.

Self Cite

217

187

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“…A better understanding of the mechanisms and rate-limiting factors controlling plant Se uptake and assimilation will be vital for the optimal use of plants to alleviate dietary Se deficiency or for cleanup of Se-polluted areas. Several transgenic plants with enhanced Se accumulation and resistance have already been developed Agalou et al, 2005;Bañ uelos et al, 2005Bañ uelos et al, , 2007Van Hoewyk et al, 2005) and may be useful for Se phytoremediation (for review, see Pilon-Smits and Freeman, 2006). The new knowledge obtained here of the genes and processes that impact Se accumulation and resistance in Arabidopsis may lead to further development of plants with increased Se content.…”

Section: Resultsmentioning

confidence: 99%

Cooperative Ethylene and Jasmonic Acid Signaling Regulates Selenite Resistance in Arabidopsis

2008

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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.

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“…Selenate treatment reduces the cysteine and reduced glutathione (GSH) contents in plants and induces the accumulation of sulfate transporters that facilitate the uptake and translocation of sulfate from roots to shoots (Takahashi et al 2000;Yoshimoto et al 2002). Selenate treatment appears to mimic sulfurdeficient stress by disturbing sulfur metabolism (Ellis and Salt 2003;Van Hoewyk et al 2005). Alternatively, unknown mechanisms for detoxification of seleniumcontaining metabolites may promote the assimilatory sulfur metabolism, including transport and reduction processes.…”

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confidence: 99%

Sulfur-responsive promoter of sulfate transporter gene is potentially useful to detect and quantify selenate and chromate

Maruyama‐Nakashita

Inoue

Saito

et al. 2007

Plant Biotechnology

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Heavy metals are highly toxic for living organisms when excess amounts exist in the environment (Salt et al. 1998;Kovalchuk et al. 2001). Soils and water contaminated with heavy metals cause major environmental and human health problems. During the last few decades, phytoremediation and plant-based assays for cleanup and monitoring of these contaminated environments have been developed (Salt et al. 1998;Kovalchuk et al. 2001;Krizek et al. 2003;Pilon-Smits 2005). These methods take advantage of the sedentary nature of plants, providing inexpensive and nontechnical means of environmental analysis and restoration (Kovalchuk et al. 2001;Krizek et al. 2003).Among heavy metals, selenium and chromium function as toxic analogs of sulfur, and they exist in nature mainly as selenate (SeO 4 2Ϫ) and chromate (CrO 4 2Ϫ ) anions at ϩ6 oxidation states. Because of their structural similarities to sulfate (SO 4 2Ϫ ), selenate and chromate are readily imported into plant cells through the activities of sulfate transporters. In fact, selenate competitively inhibits the influx of sulfate, and after incorporation into the cells, it is subsequently assimilated into selenocysteine and seleno-methionine by sharing the pathways of sulfur metabolism; ultimately, these seleniumcontaining amino acids are incorporated into proteins (Terry et al. 2000;Ellis and Salt 2003). Chromate also has an inhibitory effect on sulfate uptake, but is mainly reduced to ϩ3 oxidation states, Cr 3ϩ or Cr 2 O 3 , presumably by using reducing cofactors. Accordingly, excess amounts of selenate and chromate taken up from the environment can affect the cellular function of living organisms and sometimes have lethal effects. Indeed, several mutants lacking sulfate transporter genes have been isolated from yeast and plants by using the toxic effects of selenate and chromate as sulfate analogs (Smith et al. 1995a, b;Cherest et al. 1997;Shibagaki et al. 2002).In Arabidopsis, two high-affinity sulfate transporters, SULTR1;1 and SULTR1;2, facilitate the initial uptake of sulfate into the roots (Takahashi et al. 2000;Vidmar et al. 2000;Shibagaki et al. 2002; Yoshimoto et al. 2002). These transporters are expressed in the epidermis and cortex of roots, and their transcripts can accumulate through sulfur depletion to maximize sulfate uptake for efficiently using limited amounts of sulfur in the soil environment (Takahashi et al. 2000;Vidmar et al. 2000;Shibagaki et al. 2002; Yoshimoto et al. 2002). The expression of these SULTRs depends on the promoter activities of their 5Ј-regions controlled by sulfur deficiency (Maruyama-Nakashita et al. 2004a, b, 2005. The presence of a specific sulfur-responsive cis-element in the SULTR1;1 promoter region further elaborates the Abstract Plant-based assays for monitoring contaminated environments provide inexpensive and nontechnical means of environmental analysis. Here we report a model system for monitoring selenium and chromium, which are highly toxic heavy metals for living organisms. The major forms of selenium and chromium ...

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Overexpression of AtCpNifS Enhances Selenium Tolerance and Accumulation in Arabidopsis

Cited by 124 publications

References 42 publications

Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata

Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata

Cooperative Ethylene and Jasmonic Acid Signaling Regulates Selenite Resistance in Arabidopsis

Sulfur-responsive promoter of sulfate transporter gene is potentially useful to detect and quantify selenate and chromate

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