Exclusion of Selenium from Proteins of Selenium-Tolerant Astragalus Species

Abstract

Protein fractions 3 Se-tolerant [A. bisulcatus, A. crotalariae, A. beathii] and 3 Se-sensitive [A. lentiginosus, A. douglasii, A. palmeri] Astragalus spp., grown in the presence of [75Se]selenate, were analyzed for their Se content. Though tolerant species are known to accumulate considerably more Se than do sensitive plants, protein fractions from the 3 Se accumulators were found to contain significantly less Se (0.46-0.57 pmol Se/mg protein) than did protein fractions from the 3 nonaccumulators (4.17-5.02 pmol Se per mg protein). Under similar conditions, seedlings of Vigna radiata (L.) Wilczek had taken up Se (6.31 pmol Se/mg protein) at levels comparable to those observed in the proteins of the nonaccumulator Astragalus. The ability to tolerate and to circumvent the toxic effects of Se, characteristic of the accumulator species of Astragalus was established and is associated with a reduced incorporation of this element into protein.