Chemical form and distribution of selenium and sulfur in the selenium hyperaccumulator Astragalus bisulcatus

I J Pickering, Carrie Wright, B Bubner, D Ellis, M W Persans, E Y Yu, G N George, R C Prince, D E Salt

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Abstract

In its natural habitat, Astragalus bisulcatus can accumulate up to 0.65% (w/w) selenium (Se) in its shoot dry weight. X-ray absorption spectroscopy has been used to examine the selenium biochemistry of A. bisulcatus. High concentrations of the nonprotein amino acid Se-methylseleno-cysteine (Cys) are present in young leaves of A. bisulcatus, but in more mature leaves, the Se-methylseleno-Cys concentration is lower, and selenate predominates. Seleno-Cys methyltransferase is the enzyme responsible for the biosynthesis of Se-methylseleno-Cys from seleno-Cys and S-methyl-methionine. Seleno-Cys methyltransferase is found to be expressed in A. bisulcatus leaves of all ages, and thus the biosynthesis of Se-methylseleno-Cys in older leaves is limited earlier in the metabolic pathway, probably by an inability to chemically reduce selenate. A comparative study of sulfur (S) and Se in A. bisulcatus using x-ray absorption spectroscopy indicates similar trends for oxidized and reduced Se and S species, but also indicates that the proportions of these differ significantly. These results also indicate that sulfate and selenate reduction are developmentally correlated, and they suggest important differences between S and Se biochemistries.

Original languageEnglish
Pages (from-to)1460-1467
Number of pages8
JournalPlant Physiology
Volume131
Issue number3
DOIs
Publication statusPublished - Mar 2003

Keywords

  • ray-absorption spectroscopy
  • non-accumulator plants
  • cancer prevention
  • ATP sulfurylase
  • selenate uptake
  • Indian mustard
  • leaf tissue
  • amino-acids
  • tolerance
  • metabolism

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