Aspects of Selenium Metabolism in Higher Plants

Selenium Volatiles as Proxy to the Metabolic Pathways of Selenium in Genetically Modified Brassica juncea

“…In contrast to that, cabbage plants (Se non-accumulators) contained CH3-SeCH3 as the only [major] Se-containing volatile (15). The marked differences in the observed Se-volatile profiles served as a tool to distinguish between the accumulator and nonaccumulator plants even at the early stages of research in this area (16). In this study we expand on the use of the volatile Se profiles to follow the genetic modifications that increase Se accumulation thus making B. juncea more apt for Se phytoremediation.…”

Regulation of Sulfate Uptake by Excised Barley Roots in the Presence of Selenate

“…Active transport was evaluated within 3 hr of root-solution contact, during which the S + Se metabolized was negligible in comparison with that accumulated as inorganic ions in the inner space. In spite of the abovestated absence of discrimination at the level of active transport, plants have been shown to assimilate S or Se preferentially according to the species and its evolutionary adaptation to the Se content of soils (10).In the present work we have evaluated the S-Se uptake ratio in barley roots during 60 hr of root-solution contact in order to ascertain whether a selective mechanism is present in roots when the assimilation process is fully operating. We have also evaluated within the same 60-hr period the S-Se ratio in the free amino acid pool and in proteins to get information about the discrimination site.…”

“…Active transport was evaluated within 3 hr of root-solution contact, during which the S + Se metabolized was negligible in comparison with that accumulated as inorganic ions in the inner space. In spite of the abovestated absence of discrimination at the level of active transport, plants have been shown to assimilate S or Se preferentially according to the species and its evolutionary adaptation to the Se content of soils (10).…”

Utilization of Selenocysteine by a Cysteinyl-tRNA Synthetase from Phaseolus aureus

“…According to this hypothesis, both the sulfur and selenium amino acids are activated and incorporated into proteins; these altered proteins, with an excess of selenoamino acids, function abnormally (7,29). On the other hand, tolerance of selenium, notably in selenium-accumulator plants, is thought to have arisen from evolutionary modifications to these aminoacyl-tRNA synthetases so that the selenium isologs, no longer activated, are excluded from proteins; instead, the selenium isologs are converted to and accumulate as nonprotein selenoamino acids (7,24,28,31). Altered aminoacyl-tRNA synthetases have been described in other plants which synthesize large amounts of nonprotein amino acids.…”

“…Reports that this selenoamino acid occurs in proteins of other organisms have not always met the criticism that artifacts may have arisen during the identification procedure (27). Since selenium does not always follow the sulfur pathway (27,28), it is conceivable that selenocysteine might be excluded from some step in the protein synthesis pathway.…”