Masanao Umebayashi

Effects of zinc deficiency on the growth, proteins, and other constituents of yeast, Saccharomyces cerevisiae, cells

Abstract To carry out a series of experiments in order to analyze the effects of Zn deficiency on protein synthesis in higher plants, we used a budding yeast, Saccharomyces cerevisiae, as model organism. Yeast cells were cultured in a chemically defined Burkholder minimum medium with and without Zn. When the Zn concentration in the cells decreased to a level of less than 100 mg kg-1 dry weight, cell growth was depressed. The cells in the —Zn culture swelled, and after further culture, they formed clusters. Zinc deficiency enhanced the Ca concentration in the cells and did not affect the K and Mg concentrations. Zinc deficiency remarkably depressed the protein content of the cells. Some soluble proteins and peptides disappeared and some proteins and peptides appeared in the —Zn culture. pI of one protein shifted from 8.0 to 7.8 in the —Zn culture under nondenaturing conditions, and the N-terminal amino acid sequence of this protein showed a 100% homology with enolase (EC 4.2.1.11).

Effects of zinc deficiency on peptide synthesis in cultured tobacco plant cells

Abstract Zinc deficiency remarkably depressed the growth of cultured tobacco cells. When the zinc concentration in the cells decreased to a level of less than 70 μg/g DW, the 80S ribosome content of the cells was remarkably reduced. The decrease in the zinc concentration to a level of less than 50 μg/g DW caused a decrease in the protein content. SDS-PAGE patterns of proteins showed that the composition of the protein remained almost unchanged, although the amount was remarkably reduced.

Characterization of cadmium-binding complexes from the roots of cadmium treated rice plant

Cadmium-binding complexes were isolated from the roots of cadmium-treated rice plant. Extractant was chromatographed on a Sephadex G-50 column and the fractions, rich in SH group and cadmium, were purified further by chromatography on DEAE-Sephadex A-25. The resulting complex preparation had an apparent molecular weight of 5,600, contained 44% cysteine and 39% glutamate and lacked in aromatic amino acids. The cadmium: cysteine ratio was 1 : 2. Spectroscopic measurements indicated the presence of a cadmium-mercaptide bonding. The rice roots produced metallothionein-like substances when they were exposed to cadmium.

Effect of Shading on Zinc Deficiency Symptoms in Rice Plant

Abstract Under Zn deficiency, some major deficiency symptoms were observed on rice plants, i.e., reduction of young leaf elongation and development of necrosis on the expanded leaves. To clarify the former phenomena, the physiological role of Zn was studied from the standpoint of protein synthesis (Kitagishi and Obata 1986; Obata et al. 1994, 1996) and metabolism of auxin (Takaki and Arita 1986; Domingo et al. 1992). In contrast, the direct cause of the latter phenomenon has not yet been studied.

Cadmium tolerance of calli induced from roots of plants with differences in cadmium tolerance

Abstract The Cd tolerance of higher plants varies with the plant family (Kuboi et al. 1987). To analyze the mechanism of Cd tolerance of intact plants with differences in Cd tolerance, we compared the Cd tolerance of calli induced from roots of plants with differences in Cd tolerance. The Cd-resistant cultured cells selected from parental cells subjected to Cd stress produced Cd-binding SH compounds in much larger quantities than the parental cells (J ackson et al. 1987).

STUDIES ON AMINOACYLASE IN HIGHER PLANTS : VI. Aminoacylase in the Seeds of Grasses

Abstract Aminoacylase which catalyzes the hydrolysis of N-acyl-L-amino acids has been reported to be present both in animal and plant tissues. BEIRNBAUM et al. (1) obtained the purified preparations from hog kidney and classified them into two different aminoacylases according to their substrate specificity : aminoacylase I hydrolyzed a variety of N-acetyl amino acid while aminoacylase I1 attacked only N-acetyl- aspartic acid. Recently aminoacylase from microbial sources has been concentrated and purified to employ active preparations in the resolution of racemic amino acids (2–4).

PRODUCTION OF SH-COMPOUNDS IN A SELECTED TOBACCO CELL LINE RESISTANT TO CADMIUM

Higher plants produce metallothionein-like substances, poly(y-glutamylcys-teinyl)glycine, when exposed to heavy metals. Several authors (Bennetzen and Adams 1984; Jackson et al. 1984, 1987; Rauser 1984; Steffens et al. 1986; Grill et al. 1987) have suggested that these substances may act as scavengers of heavy metal ions such as mammalian metallothioneins. However, information about the relation between these substances and heavy metal tolerance is limited and there are few reports in which the chemical forms of Cd were compared in Cd-tolerant and Cd-sensitive cells or plants.

Effects of Cd on the fluxes of K+ and H+ in excised roots

Abstract As a result of Cd treatment, K concentrations decreased in Cd sensItive maize and kidney bean calli (Obata et al. 1994) and in intact roots of kidney bean plants (Obata et al. unpublished). Potassium may be extruded from the roots or the absorption of K may be depressed by the Cd treatment in these Cd sensitive plants. Obata et al. (1996) observed that Cd inhibited both the efflux of H+ and influx of K+ following K+ addition in intact roots of bean. Thus Cd may affect the activity of proteins essential to ion movement., i.e. ioncarriers, channels and ATPase embedded in the membranes and/or may affect the permeability of the lipids of the membrane.