Selection of tobacco cell lines resistant to selenoamino acids

Flashman, S.M.; Filner, Philip

doi:10.1016/0304-4211(78)90100-1

Cited by 14 publications

(5 citation statements)

References 7 publications

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“…Selenite is a little more toxic to plants than selenate probably because selenite is more stable at the Eh-pH conditions of normal soils (Fig 10). The toxicity ofselenite increases with increased sulphur concentrations in the medium, whilst selenate is toxic to tissue cultures of higher plants (Flashman and Filner 1978). Symptoms of selenium toxicity to crop plants are recognised by interveinal chlorosis or black spots, bleaching or yellowing of younger leaves, and pinkish spots on roots.…”

Section: Deficiency and Toxicitymentioning

confidence: 99%

Effects of selected trace elements on plant growth

Aller¹,

Bernal²,

Nozal³

et al. 1990

J Sci Food Agric

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Truce elemerits in plurits Lire : tittrniunz, uaiiutlium, cobult, nickel, uluniiiiiutiz, silicoti, ursenic, seletiium, Juoritie und INTROD UCTlONIt is known that living organisms require only small amounts of some elements as nutrients. The effects they produce must be very important, since they appear to participate in key biocatalytic events. The essentiality of an element is established when specific and direct beneficial effects on aspects of growth or metabolism are found, normally by growing agronomic species in purified cultures in which this element was previously added; the omission of the element causes a directly In agricultural ecosystems plants play an important role in the cycling of trace elements, but the role of these trace elements in plant growth is mostly unknown (Aller and Bernal 1986). Although some processes can be activated by a certain number of these trace elements, new research is also necessary in order to determine their biochemical functions in higher plants and establish their general essentiality. Some of these elements (titanium, vanadium, cobalt, nickel, aluminium, silicon, arsenic, selenium, fluorine and iodine) are reviewed in this paper.The elements considered here are known to have beneficial effects on some groups or species but their general essentiality requires confirmation. Interest in these trace elements, which are usually present in plants in small quantities, arises for different reasons. They stimulate plant growth when they are present at small concentrations, although not necessarily under all conditions. Some of them are essential elements for animal nutrition and may be present in amounts large enough to limit the agricultural usefulness of some areas. The content of some elements, such as aluminium, titanium and silicon, in agricultural soils are usually sufficient Aller and Deban 1989); however, we refer to them in the text as trace elements since these elements are used by plants in small quantities for their nutrition.Ingestion of plant foodstuffs is the primary route of entry of trace elements into humans. In turn, the life of man largely depends on the quantity and quality of his food. However, the ability of plants to accumulate trace elements is certainly limited, being affected by several factors such as plant species, plant parts and age, soil and climatic conditions etc. Consequently, research in the field of micronutrients focuses usually on their uptake mechanisms, distribution pathway in the plant, biochemical functions, and deficiency and toxicity levels and states. These are therefore the items covered in this survey. TITANIUM Absorption, transport and accumulationThe aqueous solution chemistry of elements is very complex because of the number of different oxidation states and the formation of oxyions, hydroxyl and probably also organic complexes in different pH regions. Under certain conditions the dissolved species may be in equilibrium with solids. We therefore consider that a convenient way to summarise the chemistry of such a s...

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Section: Deficiency and Toxicitymentioning

confidence: 99%

Effects of selected trace elements on plant growth

Aller¹,

Bernal²,

Nozal³

et al. 1990

J Sci Food Agric

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“…This frequency of origination is much higher than the 10-7 to 10-8 which has been encountered in selections for other biochemical variants (mutants?) of the XD cells (7,10,29).…”

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confidence: 99%

Resistance to Acetohydroxamate Acquired by Slow Adaptive Increases in Urease in Cultured Tobacco Cells

Yamaya¹,

Filner²

1981

Plant Physiol.

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“…Most recent studies concerned with the interactions of selenocompounds in plant systems have been carried out with the intact plant or with cultured cells (6,11,22). A few comparable in vitro plant studies have focused on the following three aspects of selenium biochemistry: (a) aminoacylation of tRNA with selenoamino acids (2,3,21,24); (b) interactions of selenomethionine with methionine adenosyltransferase (12); and (c) the translational incorporation of selenomethionine into protein (5).…”

Section: Discussionmentioning

confidence: 99%

Selenium Toxicity: Aminoacylation and Peptide Bond Formation with Selenomethionine

Eustice¹,

Kull²,

Shrift³

1981

Plant Physiol.

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Selenomethionine and methionine were compared as substrates for in vitro aminoacylation, ribosome binding, and peptide bond formation with preparations from wheat germ. Selenomethionine paralleled methionine in all steps of the translation process except peptide bond formation. Peptide bond formation with the initiating species of tRNAMet demonstrated that selenomethionyl-tRNAM't was less effective as a substrate than was methionyl-tRNAf't. Participation of selenomethionine in the initiation process of translation could be expected to reduce the overall rate of protein synthesis and might aid in explaining selenium toxicity in selenium-sensitive plants.methionine, each step enroute to incorporation of this amino acid into protein should be studied independently of the other. For this purpose, ribosomes and supernatant fractors, prepared from wheat germ, were used. Selenomethionine and methionine functioned as equivalent substrates in the aminoacylation reaction and in ribosome binding of the aminoacyl-tRNA. Peptide bond formation between puromycin and selenomethionine, in contrast, was curtailed compared to bond formation between puromycin and methionine. As an explanation for selenium toxicity at the subcellular level, it would appear that selenomethionine exerts one of its effects in wheat by limiting the rate at which the first peptide bond is formed during protein synthesis. MATERIALS AND METHODSMethionine is a key intermediate in several crucial metabolic reactions. Since methionine contains a sulfur atom, substances which disrupt sulfur metabolism, such as those that contain selenium, in all likelihood will interfere with the metabolism of this sulfur amino acid. In selenium-sensitive plants, the assimilation of selenium usually parallels that of sulfur. As a consequence, selenoanalogs of several sulfur-containing metabolites can be synthesized (17). One of these analogs, selenomethionine, is known to be formed by a wide variety of plants (7,9,(16)(17)(18). Although the biochemical characteristics of selenomethionine resemble those of methionine in a great many ways, the metabolic activity of selenomethionine apparently differs in certain respects; one of these differences is, in general, reaction rate (4,5,11,12). Examination of those reactions in which selenomethionine functions at a rate different than methionine could reveal some of the factors that underlie selenium toxicity.One vital metabolic process with which these methionine analogs might interfere is the biosynthesis of protein. Methionine, required as the initiating amino acid during the translation process, is also incorporated at internal positions of most protein chains. Alteration of initiation process of translation or with the chain elongation process could drastically affect normal functions of the cell. Previous in vitro studies with polysomes from Vigna radiata root tips have established that methionine is a slightly better substrate than is selenomethionine during chain elongation, provided that both amino acids are supplied s...

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Selection of tobacco cell lines resistant to selenoamino acids

Cited by 14 publications

References 7 publications

Effects of selected trace elements on plant growth

Effects of selected trace elements on plant growth

Resistance to Acetohydroxamate Acquired by Slow Adaptive Increases in Urease in Cultured Tobacco Cells

Selenium Toxicity: Aminoacylation and Peptide Bond Formation with Selenomethionine

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