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PubMed2005

Expression of plant cyclic nucleotide-gated cation channels in yeast.

The functional properties of inwardly conducting plant cyclic nucleotide-gated cation channels (CNGCs) have not been thoroughly characterized due in part to the recalcitrance of their functional expression in heterologous systems. Here, K+ uptake-deficient mutants of yeast (trk1,2) and Escherichia coli (LB650), as well as the Ca2+-uptake yeast mutant mid1,cch1, were used for functional characterization of Arabidopsis thaliana CNGCs, with the aim of identifying some of the cultural and physiological conditions that impact on plant CNGC function in heterologous systems. Use of the Ca2+-uptake yeast mutant provided the first evidence consistent with Ca2+ conduction by the A. thaliana CNGC AtCNGC1. Expression of AtCNGC1 in LB650 demonstrated that mutants of Escherichia coli (which has no endogenous calmodulin) can also be used to study functional properties of CNGCs. Expression of AtCNGC2 and AtCNGC4 enhanced growth of trk1,2 in the presence of hygromycin; AtCNGC1 has less of an effect. Deletion of the AtCNGC1 calmodulin-binding domain enhanced growth of trk1,2 at low external K+ but not of LB650, suggesting that yeast calmodulin may bind to, and down-regulate this plant channel. In vitro binding studies confirmed this physical interaction. Northern analysis, green fluorescent protein:AtCNGC1 fusion protein expression, as well as an antibody raised against a portion of AtCNGC1, were used to monitor expression of AtCNGC1 and deletion constructs of the channel in the heterologous systems. In the presence of the activating ligand cAMP, expression of the AtCNGC1 channel with the calmodulin-binding domain deleted increased intracellular [K+] of trk1,2. Trk1,2 is hypersensitive to the toxic cations spermine, tetramethylamine, and NH4+. These compounds, as well as amiloride, inhibited trk1,2 growth and thereby improved the efficacy of this yeast mutant as a heterologous expression system for CNGCs. In addition to characterizing mutants of yeast and E. coli as assay systems for plant CNGCs, work presented in this report demonstrates, for the first time, that a plant CNGC can retain ion channel function despite (partial) deletion of its calmodulin-binding domain and that yeast calmodulin can bind to and possibly down-regulate a plant CNGC.

Arabidopsis↗
PubMed1993

Yeast open reading frame YCR14C encodes a DNA beta-polymerase-like enzyme.

We have shown by activity gel that overexpression in E. coli of a yeast chromosome 3 open reading frame (ORF) designated YCR14C and bearing homology to mammalian DNA polymerases beta results in a new DNA polymerase in the host cells. The molecular mass of this enzyme corresponded to the YCR14C-predicted 67 kDa protein, and NH2-terminal amino acid sequencing confirmed that the expressed protein was encoded by the yeast ORF. This new yeast DNA polymerase was purified to homogeneity from E.coli. In a fashion similar to that of mammalian beta-polymerases, the purified yeast enzyme exhibited distributive DNA synthesis on DNA substrate with a single-stranded template and processive gap-filling synthesis on a short-gapped DNA substrate. Activity of this yeast beta-polymerase-like enzyme was sensitive to the beta-polymerase inhibitor ddNTP and resistant to both 1 mM NEM and neutralizing antibody to E. coli DNA polymerase I. These results, therefore, indicate that YCR14C encodes a DNA beta-polymerase-like enzyme in yeast, and we name it DNA polymerase IV. Yeast strains harboring a deletion mutation of the pol IV gene are viable, they exhibit no increase in sensitivity to ultraviolet light, ionizing radiation or alkylating agents, and sporulation and spore viability are not affected in the mutant.

Amino Acid Sequence↗
PubMed2001

Stable expression in yeast of the mature form of human telomerase RNA depends on its association with the box H/ACA small nucleolar RNP proteins Cbf5p, Nhp2p and Nop10p.

Telomerase is a ribonucleoprotein (RNP) particle required for the replication of telomeres. The RNA component, termed hTR, of human telomerase contains a domain structurally and functionally related to box H/ACA small nucleolar RNAs (snoRNAs). Furthermore, hTR is known to be associated with two core components of H/ACA snoRNPs, hGar1p and Dyskerin (the human counterpart of yeast Cbf5p). To assess the functional importance of the association of hTR with H/ACA snoRNP core proteins, we have attempted to express hTR in a genetically tractable system, Saccharomyces cerevisiae. Both mature non-polyadenylated and polyadenylated forms of hTR accumulate in yeast. The former is associated with all yeast H/ACA snoRNP core proteins, unlike TLC1 RNA, the endogenous RNA component of yeast telomerase. We show that the presence of the H/ACA snoRNP proteins Cbf5p, Nhp2p and Nop10p, but not Gar1p, is required for the accumulation of mature non-polyadenylated hTR in yeast, while accumulation of TLC1 RNA is not affected by the absence of any of these proteins. Our results demonstrate that yeast telomerase is unrelated to H/ACA snoRNPs. In addition, they show that the accumulation in yeast of the mature RNA component of human telomerase depends on its association with three of the four core H/ACA snoRNP proteins. It is likely that this is the case in human cells as well.

DNA, Recombinant↗
PubMed2001

Monitoring S phase progression globally and locally using BrdU incorporation in TK(+) yeast strains.

Eukaryotic chromosome replication is initiated from numerous origins and its activation is temporally controlled by cell cycle and checkpoint mechanisms. Yeast has been very useful in defining the genetic elements required for initiation of DNA replication, but simple and precise tools to monitor S phase progression are lacking in this model organism. Here we describe a TK(+) yeast strain and conditions that allow incorporation of exogenous BrdU into genomic DNA, along with protocols to detect the sites of DNA synthesis in yeast nuclei or on combed DNA molecules. S phase progression is monitored by quantification of BrdU in total yeast DNA or on individual chromosomes. Using these tools we show that yeast chromosomes replicate synchronously and that DNA synthesis occurs at discrete subnuclear foci. Analysis of BrdU signals along single DNA molecules from hydroxyurea-arrested cells reveals that replication forks stall 8-9 kb from origins that are placed 46 kb apart on average. Quantification of total BrdU incorporation suggests that 190 'early' origins have fired in these cells and that late replicating territories might represent up to 40% of the yeast genome. More generally, the methods outlined here will help understand the kinetics of DNA replication in wild-type yeast and refine the phenotypes of several mutants.

Blotting, Southern↗
PubMed1978

Detection of yeast ribosomal RNA sequences in E. coli infected with hybrid bacteriophage.

Yeast ribosomal DNA was inserted into Escherichia coli on a bacteriophage vector and the host cell RNA was then extracted and analyzed for the presence of yeast ribosomal RNA sequences. RNA complementary to yeast rDNA was detected by hybridization. The transcription of yeast rDNA was found to be independent of phage RNA synthesis and to occur on the same DNA strand as rRNA transcription in yeast. However, hybridization to restriction fragments of yeast rDNA suggested that the RNA species detected in E. coli differ somewhat from authentic yeast rRNA.

Base Sequence↗
PubMed2004

Functions of yeast helicase Ssl2p that are essential for viability are also involved in protection from the toxicity of adriamycin.

We have found that, in the yeast Saccharomyces cerevisiae, overexpression of the DNA helicase Ssl2p confers resistance to adriamycin. Ssl2p is involved, as a subunit of the basic transcription factor TFIIH, in the initiation of transcription and in nucleotide-excision repair (NER), and this helicase is essential for the survival of yeast cells. An examination of the relationship between the known functions of Ssl2p and adriamycin resistance indicated that overexpression of Ssl2p caused little or no increase in the rate of RNA synthesis and in NER. The absence of any involvement of NER in adriamycin resistance was supported by the finding that yeast cells that overexpressed the mutant form of Ssl2p that lacked the carboxy-terminal region, which is necessary for NER, remained resistant to adriamycin. When we examined the effects of overexpression in yeast of other mutant forms of Ssl2p with various deletions, we found that, of the 843 amino acids of Ssl2p, the entire amino acid sequence from position 81 to position 750 was necessary for adriamycin resistance. This region is identical to the region of Ssl2p that is necessary for the survival of yeast cells. Although this region contains helicase motifs, the overexpression of other yeast helicases, such as Rad3 and Sgs1, had little or no effect on adriamycin resistance, indicating that a mere increase in the intracellular level of helicases does not result in adriamycin resistance. Our results suggest that the functions of Ssl2p that are essential for yeast survival are also required for protection against adriamycin toxicity.

Antibiotics, Antineoplastic↗
PubMed1991

A site-directed mutagenesis study of yeast calmodulin.

A site-directed mutagenesis study was carried out in order to understand the regulatory mechanism of calmodulin. We started from the yeast (Saccharomyces cerevisiae) calmodulin gene since it has many differences in amino acid sequence and inferior functional properties compared with the vertebrate calmodulin. Recombinant yeast calmodulins were generated in Escherichia coli transformed by constructed expression plasmids. Three recombinant calmodulins were obtained. The first two were YCM61G, in which the Ca2(+)-binding site 2 (the four Ca2(+)-binding EF-hand structures in calmodulin were numbered from the N-terminus) was converted to the same as that in vertebrate calmodulin, and YCM delta 132-148, in which the C-terminal half sequence of site 4 was deleted. These two recombinant calmodulins had the same maximum Ca2+ binding (3 mol/mol) as yeast calmodulin, which indicates that site 4 of yeast calmodulin was the one losing Ca2+ binding capacity. YCM delta 132-148 could not activate target enzymes, whereas its Ca2+ binding profile was similar to those of yeast calmodulin and YCM61G. Therefore, the structure in site 4 which cannot bind Ca2+ is indispensable for the regulatory function of yeast calmodulin. The complete regulatory function of vertebrate calmodulin can be attained by the combination of 4 Ca2+ binding structures. The negative charge cluster in the central alpha-helix region is suggested to stabilize the active conformation of calmodulin, since the third yeast calmodulin mutant, YCM83E, which had the negative charge cluster, increased the maximum activation of myosin light chain kinase.

Amino Acid Sequence↗
PubMed1991

Characterization of Rarobacter faecitabidus protease I, a yeast-lytic serine protease having mannose-binding activity.

Rarobacter faecitabidus protease I, a yeast-lytic serine protease, was characterized in order to elucidate the mechanism of lysis of yeast cells by this enzyme. The N-terminal amino acid sequence of the enzyme was found to be homologous to those of Lysobacter enzymogenes alpha-lytic protease and Streptomyces griseus proteases A and B around the catalytic His residue, showing that it is a mammalian type serine protease. In a study of its substrate specificity, it preferentially hydrolyzed the ester of alanine among amino acid p-nitrophenylesters. It also efficiently hydrolyzed succinyl Ala-Pro-Ala p-nitroanilide, the specific synthetic substrate for pancreatic elastase. With oxidized insulin B-chain, it hydrolyzed almost exclusively the peptide bond between valine 18 and cysteic acid 19 in the early step of the reaction, and thereafter it partially hydrolyzed Val12-Glu13, Ala14-Leu15, and Leu15-Tyr16. These results indicate that Rarobacter protease I is elastase-like in its substrate specificity, preferentially hydrolyzing the peptide bond of aliphatic amino acids. Its affinity for yeast cells was also investigated, and while Rarobacter protease I was adsorbed by yeast cells, pancreatic elastase was not. This difference was thought to account for the failure of pancreatic elastase to lyse yeast cells, even though its specificity is similar to that of the yeast-lytic enzyme. Rarobacter protease I was adsorbed by a mannose-agarose column and specifically eluted from the column with a buffer containing D-mannose or D-glucose. These monosaccharides also inhibited its yeast-lytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗
PubMed2005

Effect of supplementing selenium yeast in diets of laying hens on egg selenium content.

An 8-wk experiment was conducted using 90 Hy-Line W-98 hens (26 wk of age) to evaluate the use of organic Se from Se yeast as an Se source for laying hens. At 22 wk of age, the hens were placed on a low Se corn-soybean meal pretest diet for 4 wk. At the end of the pretest period, hens were placed on 1 of 3 experimental treatments; the low Se diet without supplementation (basal diet), basal diet with 0.3 ppm of Se added from sodium selenite, or basal diet with 0.3 ppm of Se added from Se yeast. Diets contained 0.11, 0.38, and 0.34 ppm Se for basal, basal plus sodium selenite, and basal plus Se yeast diets, respectively. The experimental diets were each fed to 10 replicate groups of 3 hens for 8 wk (26 to 34 wk of age). Selenium levels in eggs (mg/kg of whole egg) were analyzed at 0, 4, and 8 wk. Egg Se contents at 0 wk were similar among treatments. Eggs from hens fed the 2 Se-fortified diets had higher (P < 0.01) Se concentrations than did eggs from hens fed the low Se diet at 4 and 8 wk. The Se yeast diet also yielded levels of egg Se that were significantly higher (P < 0.01) than those from the sodium selenite diet at 4 and 8 wk. The Se yeast resulted in a 4.8-fold increase in egg Se concentration compared with a 2.8-fold increase for the sodium selenite diet over the unsupplemented diet at 8 wk (0.065, 0.182, and 0.311 ppm for the control, sodium selenite, and Se yeast diets, respectively). There were no differences in egg production, egg weight, feed intake, or mortality among treatments. Results of this study indicate that use of Se yeast in laying hens diets is very effective for increasing the Se content of eggs.

Animal Feed↗
PubMed2004

Vaginal yeast colonization in nonpregnant women: a longitudinal study.

OBJECTIVE: We sought to investigate the prevalence and risk factors for vaginal yeast colonization over a 1-year period. METHODS: We conducted a longitudinal cohort study of 1,248 asymptomatic young women by collecting demographic and behavioral data at baseline, 4, 8, and 12 months. RESULTS: Seventy percent of women were colonized by vaginal yeast at one or more visits, but only 4% were colonized at all 4 visits. Using an adjusted generalized estimating equation model, factors associated with vaginal yeast colonization were marijuana use in the previous 4 months, depomedroxyprogesterone acetate use in the past 4 months, sexual intercourse in the previous 5 days, and concurrent colonization with lactobacilli and group B streptococcus. Symptoms of pruritus and vulvovaginal burning were associated with yeast colonization, but antifungal use was not. CONCLUSION: Recent sexual intercourse and use of injection contraceptives are risk factors for yeast colonization. Rates of antifungal use did not show an association with yeast colonization. The reporting of antifungal use by women lacking yeast colonization suggests that self-diagnosis is inaccurate. LEVEL OF EVIDENCE: II-2.

Adolescent↗
PubMed1998

Structure and genetic stability of mitochondrial genomes vary among yeasts of the genus Saccharomyces.

Several yeast species/isolates belonging to the genus Saccharomyces were examined for the organization of their mtDNAs and ability to generate petite mutants. A general characteristic for all of the mtDNAs tested was that they were very A+T-rich. However, restriction patterns and inducibility of petite mutations revealed a great diversity in the organization and genetic behaviour of mtDNAs. One group of yeasts, Saccharomyces sensu stricto, contains mtDNA ranging in size from 64 to 85 kb. mtDNAs form these yeasts contain a high number of restriction sites that are recognized by the enzymes Haelll and Mspl, which cut specifically in G+C clusters. There are three to nine ori/rep sequences per genome. These yeasts spontaneously generate respiration deficient mutants. Ethidium bromide (Et-Br), at low concentrations, induces a majority of cells to give rise to petites. A second group of yeasts, Saccharomyces sensu lato, contains smaller mtDNAs, ranging in size from 23 to 48 kb, and probably only a few intergenic G+C clusters and no ori/rep sequences. These yeasts also generate petite clones spontaneously. but Et-Br, even when present at high concentrations, does not substantially increase the frequency of petites. In most petite clones from these yeasts only a small fragment of the wild-type molecule is retained and apparently multiplied. A third group, represented by Saccharomyces kluyveri, does not give rise to petite mutants either spontaneously or after induction.

Base Composition↗
PubMed2002

Candida davenportii sp. nov., a potential soft-drinks spoilage yeast isolated from a wasp.

During a survey of yeast ecology in a soft-drinks production facility, a dead wasp was removed from the sampling tap of an external sugar-syrup storage tank. A yeast isolated from the dead wasp was found to be similar, although not identical, in its physiological characteristics to Candida lactis-condensi and Candida stellata. Sequence analysis of the 26S rDNA D1/D2 variable domain revealed that this isolate was most closely related to C stellata, but differed sufficiently in its D1/D2 sequence to indicate that it belonged to a separate species. The yeast species has been named Candida davenportii sp. nov.; the type strain is NCYC 3013T (= CBS 9069T). C davenportii sp. nov. was osmotolerant, moderately preservative-resistant and able to grow in very acidic conditions, i.e. pH 14. This yeast grew well in fruit-containing soft drinks, cola-type beverages and a synthetic soft drink and is therefore a potential cause of spoilage of soft drinks and other sugary food products. Other related yeast species in the same taxonomic clade as C davenportii sp. nov. are also osmotolerant, growing in < 50% (w/v) sugar. Many of these species are associated with insects, specifically bees, bumblebees and leafcutter bees, and many have been reported as the causative agent of spoilage of sugary foods, such as condensed milk, fruit juices and concentrates. It is proposed that C davenportii sp. nov. and other closely related yeasts are primarily associated with Aculeates (bees and wasps). In turn, bees and wasps are attracted by sugary residues in foods such as fruit juices and concentrates, forming the source of infection of these yeasts and thus instigating spoilage.

Animals↗
PubMed2006

Predictive value of oral colonization by Candida yeasts for the onset of a nosocomial infection in elderly hospitalized patients.

The incidence of nosocomial yeast infections has increased markedly in recent decades, especially among the elderly. The present study was therefore initiated not only to determine the predictive value of oral colonization by yeasts for the onset of a nosocomial Candida infection in elderly hospitalized patients (> 65 years), but also to clarify the factors that promote infection and to establish a relationship between the intensity of oral carriage and the onset of yeast infection. During this prospective cohort study, 256 patients (156 women and 100 men with a mean age of 83 +/- 8 years) were surveyed for yeast colonization or infection. Samples were collected every 4 days from day 0 to day 16 from four sites in the mouth, and intrinsic and extrinsic factors that might promote infection were recorded for each patient. Pulsed field gel electrophoresis was performed on Candida albicans isolates from all infected patients. Poor nutritional status was observed in 81 % of the patients and hyposalivation in 41 %. The colonization level was 67 % on day 0 (59 % C. albicans) and a heavy carriage of yeasts (> 50 c.f.u.) was observed for 51 % of the patients. The incidence of nosocomial colonization reached 6.9 % on day 4 (6.1 % on day 8 and 2.7 % on day 12), and that of nosocomial infection was 3.7 % on day 4 (6.8 % on day 8, 11.3 % on day 12 and 19.2 % on day 16). Of the 35 patients infected, 57 % were suffering from oral candidiasis. The principal risk factors for colonization were a dental prosthesis, poor oral hygiene and the use of antibiotics. The risk factors for infection, in addition to those already mentioned for colonization, were endocrine disease, poor nutritional status, prolonged hospitalization and high colony counts. Genotyping revealed person-to-person transmission in two patients. Thus, this study demonstrates a significant association between oral colonization and the onset of yeast infections in elderly hospitalized patients. Therefore, oral samples should be collected at admission and antifungal treatment should be administered in cases of colonization, especially in patients presenting a heavy carriage of yeasts. Genotyping of the strains confirmed the possibility of person-to-person transmission.

Aged↗
PubMed2004

Yeast Kre1p is GPI-anchored and involved in both cell wall assembly and architecture.

Kre1p is a cell surface O-glycoprotein involved in a late stage of 1,6-beta-glucan formation in the yeast Saccharomyces cerevisiae. Disruption of KRE1 leads to a 40 % reduction in the overall 1,6-beta-glucan content of the cell wall. This paper shows that in a yeast Deltakre1 null mutant, neither an N-terminal-truncated Kre1p nor Kre1p variants lacking a C-terminal glycosylphospatidylinositol (GPI) attachment site are capable of achieving normal function in glucan assembly, while full-length Kre1p completely complements a Deltakre1 null mutation and restores cell wall 1,6-beta-glucan content up to wild-type level. In a yeast gpi1 mutant, a green-fluorescent-protein-tagged Kre1p derivative is secreted into the medium, indicating an at least transient GPI-anchoring stage of Kre1p during its processing within the yeast secretory pathway. In contrast to the severe defect in cell wall beta-d-glucan, the amount of cell wall mannoproteins is not significantly decreased in a Deltakre1 disruptant, as could be confirmed in competition assays by investigating toxin binding to isolated cell wall mannoproteins. Since the yeast Deltakre1 mutant differed in its sensitivity to zygocin and K28, two killer viral protein toxins that use different cell wall mannoprotein populations as a primary toxin receptor, it can be concluded that in a yeast Deltakre1 background, mannoproteins do not differ significantly in total amount from a Kre1+ wild-type but rather in their expression and distribution at the cell surface. Taken together, these data favour and suggest a structural, rather than enzymic, function of Kre1p in yeast cell wall assembly.

Cell Wall↗
PubMed1998

The yeast Ada complex mediates the ligand-dependent activation function AF-2 of retinoid X and estrogen receptors.

Nuclear receptors can function as ligand-inducible transregulators in both mammalian and yeast cells, indicating that important features of control of transcription have been conserved throughout evolution. Here, we report the isolation and characterization of a yeast protein that exhibits properties expected for a coactivator/mediator of the ligand-dependent activation function AF-2 present in the ligand-binding domain (LBD, region E) of the retinoid X (RXRalpha) and estrogen (ERalpha) receptors. This protein is identical to Ada3, a component of the yeast Ada coactivator complex. We demonstrate that: (1) the region encompassing residues 347-702 of Ada3 interacts with the LBD of RXRalpha and ERalpha in a ligand-dependent manner in yeast; (2) this interaction corresponds to a direct binding and requires the integrity of the core of the AF-2 activating domain (AF-2 AD) of both RXRalpha and ERalpha; (3) Ada3 as well as Ada2 and Gcn5, two other components of the Ada complex, are required for maximal AF-2 activity in yeast; and (4) Ada3 is able to enhance the AF-2 activity of RXRalpha and ERalpha when overexpressed in yeast and mammalian cells. Taken together, these data indicate that ligand-dependent transactivation by RXRalpha and ERalpha in yeast is mediated at least in part by the Ada complex, in which the Ada3 subunit directly binds to the holoreceptor LBD.

Animals↗
PubMed1988

The human c-fos serum response factor and the yeast factors GRM/PRTF have related DNA-binding specificities.

One of the elements that mediates growth factor and serum inducibility of the human c-fos gene is a region of dyad symmetry that lies between nucleotides -320 and -299 of the human gene. A mammalian protein specifically binds to this sequence element and has been termed the serum response factor (SRF). Gel-shift analysis and competition experiments demonstrate that there is a factor in the yeast Saccharomyces cerevisiae that binds specifically to the human c-fos SRE. The methylation interference pattern of the yeast factor is identical to that of the mammalian SRF. Regulatory elements of cell-type-specific genes in yeast have homologies to the c-fos SRE and complete for binding of both the mammalian and yeast factors to the SRE. Antisera to the gene product of the MCM1 locus react with the yeast SRE-binding factor. These data suggest that this yeast protein is closely related or identical to the factors [general regulator of mating type (GRM) and pheromone/receptor transcription factor (PRTF)] that are required for the regulation of cell-type-specific genes in yeast.

Cloning, Molecular↗
PubMed1992

Yeast and human TFIIDs are interchangeable for the response to acidic transcriptional activators in vitro.

Previous work showed that human TFIID fails to support yeast cell growth, although it is nearly identical to yeast TFIID in a carboxy-terminal region of the molecule that suffices for basal, TATA-element-dependent transcription in vitro. These and other findings raised the possibility that TFIID participates in species-specific interactions, possibly with mediator factors, required for activated transcription. Here, we report that human TFIID and amino-terminally truncated derivatives of yeast TFIID are fully functional in support of both basal transcription and the response to acidic activator proteins in a yeast in vitro transcription system. Conversely, and in contrast to previously published results, yeast TFIID supports both basal and activated transcription in reactions reconstituted with human components. This functional interchangeability of yeast and human TFIIDs argues strongly against species specificity with regard to TFIID function in basal transcription and the response to acidic activator proteins. In addition, our results suggest that any intermediary factors between acidic activators and TFIID are conserved from yeast to man.

Blotting, Northern↗
PubMed1996

A1 toxicity in yeast. A role for Mg?

We have established conditions in which soluble Al is toxic to the yeast Saccharomyces cerevisiae. The major modifications to a standard synthetic medium were lowering the pH and the concentration of Mg ions. Alterations to the PO4, Ca, or K concentration had little effect on toxicity. Organic acids known to chelate Al reduced its toxicity, suggesting that Al3+ is the toxic Al species. The unique ability of Mg ions to ameliorate Al toxicity led us to investigate the hypothesis that Al inhibits Mg uptake by yeast. Yeast cells accumulate Mg, Co, Zn, Ni, and Mn ions via the same transport system (G.F. Fuhrmann, A. Rothstein [1968] Biochim Biophys Acta 163: 325-330). Al3+ inhibited the accumulation of 57Co2+ by yeast cells more effectively than Ga, La, or Mg. In addition, a mutant yeast strain with a defect in divalent cation uptake proved to be more sensitive to Al than a wild-type strain. Taken together, these results suggest that Al may cause Mg deficiency in yeast by blocking Mg transport. We discuss the relevance of yeast as a model for the study of Al toxicity in plant systems.

Alum Compounds↗