Phytochelatin production in marine algae. 1. An interspecies comparison

Ahner, Beth A.; Kong, Shing; Morel, F. M. M.

doi:10.4319/lo.1995.40.4.0649

Cited by 160 publications

(116 citation statements)

References 19 publications

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“…Copper concentrations have been shown to affect community composition in coastal ecosystems (26); therefore, it came as some surprise to find that Ostreococcus lacks a gene for phytochelatin synthase for ameliorating copper toxicity (27,28). Instead, this organism contains tesmin-like metallothionein sequences and several Cu-efflux proteins.…”

Section: Resultsmentioning

confidence: 99%

The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation

Palenik

Grimwood

Aerts

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

582

532

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The smallest known eukaryotes, at Ϸ1-m diameter, are Ostreococcus tauri and related species of marine phytoplankton. The genome of Ostreococcus lucimarinus has been completed and compared with that of O. tauri. This comparison reveals surprising differences across orthologous chromosomes in the two species from highly syntenic chromosomes in most cases to chromosomes with almost no similarity. Species divergence in these phytoplankton is occurring through multiple mechanisms acting differently on different chromosomes and likely including acquisition of new genes through horizontal gene transfer. We speculate that this latter process may be involved in altering the cell-surface characteristics of each species. In addition, the genome of O. lucimarinus provides insights into the unique metal metabolism of these organisms, which are predicted to have a large number of selenocysteine-containing proteins. Selenoenzymes are more catalytically active than similar enzymes lacking selenium, and thus the cell may require less of that protein. As reported here, selenoenzymes, novel fusion proteins, and loss of some major protein families including ones associated with chromatin are likely important adaptations for achieving a small cell size.green algae ͉ picoeukaryote ͉ genome evolution ͉ selenium ͉ synteny P hytoplankton living in the oceans perform nearly half of total global photosynthesis (1). Eukaryotic phytoplankton exhibit great diversity that contrasts with the lower apparent diversity of ecological niches available to them in aquatic ecosystems. This observation, know as the ''paradox of the plankton,'' has long puzzled biologists (2). By providing molecular level information on related species, genomics is poised to provide new insights into this paradox.Picophytoplankton, with cell diameters Ͻ2 m, play a significant role in major biogeochemical processes, primary productivity, and food webs, especially in oligotrophic waters. Within this size class, the smallest known eukaryotes are Ostreococcus tauri and related species. Although more similar to flattened spheres in shape, these organisms are Ϸ1 m in diameter (3, 4) and have been isolated or detected from samples of diverse geographical origins (5-8). They belong to the Prasinophyceae, an early diverging class within the green plant lineage, and have a strikingly simple cellular organization, with no cell wall or flagella, and with a single chloroplast and mitochondrion (4). Recent work has shown that small-subunit rDNA sequences of Ostreococcus from cultures and environmental samples cluster into four different clades that are likely distinct enough to represent different species (6, 9).Here we report on the gene content, genome organization, and deduced metabolic capacity of the complete genome of Ostreococcus sp. strain CCE9901 (7), a representative of surface-ocean adapted Ostreococcus, referred to here as Ostreococcus lucimarinus. We compare it to the analogous features of the related species O. tauri strain OTH95 (10). Our results show that many process...

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Section: Resultsmentioning

confidence: 99%

The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation

Palenik

Grimwood

Aerts

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

582

532

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“…E. coli, which lack a vacuole, translocate Cd to their membranes (35) by binding Cd with glutathione, a precursor of (and functionally analogous to) phytochelatin (28). Cd is a particularly efficient metal for inducing production of metal-binding ligands in plankton (36), with analysis of field populations (37,38) and laboratory cultures (39,40) demonstrating that Cdbinding ligands are produced far in excess of that needed to sequester any intracellular Cd (and other metals, such as Cu and Zn; ref. 36).…”

Section: Discussionmentioning

confidence: 99%

Nonspecific uptake and homeostasis drive the oceanic cadmium cycle

Horner

Lee

Henderson

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

103

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The global marine distributions of Cd and phosphate are closely correlated, which has led to Cd being considered as a marine micronutrient, despite its toxicity to life. The explanation for this nutrient-like behavior is unknown because there is only one identified biochemical function for Cd, an unusual Cd/Zn carbonic anhydrase. Recent developments in Cd isotope mass spectrometry have revealed that Cd uptake by phytoplankton causes isotopic fractionation in the open ocean and in culture. Here we investigate the physiochemical pathways that fractionate Cd isotopes by performing subcellular Cd isotope analysis on genetically modified microorganisms. We find that expression of the Cd/Zn carbonic anhydrase makes no difference to the Cd isotope composition of whole cells. Instead, a large proportion of the Cd is partitioned into cell membranes with a similar direction and magnitude of Cd isotopic fractionation to that seen in surface seawater. This observation is well explained if Cd is mistakenly imported with other divalent metals and subsequently managed by binding within the cell to avoid toxicity. This process may apply to other divalent metals, whereby nonspecific uptake and subsequent homeostasis may contribute to elemental and isotopic distributions in seawater, even for elements commonly considered as micronutrients.biological fractionation | isotope geochemistry | metal homeostasis | subcellular analysis | trace metal I n addition to the macronutrients nitrate, phosphate, and silicate, marine phytoplankton require many essential metals to function correctly (1). The uptake and utilization of these micronutrients results in large vertical isotopic and concentration gradients for many transition metals in seawater (2). In the open ocean, Cd concentrations are as low as a few picomoles per kilogram (2, 3), with associated highly fractionated Cd isotopic compositions of up to several permil ( Fig. 1) (4). In culture, phytoplankton consume small quantities of Cd (5-7) and exhibit light Cd isotope compositions (8). Taken together, the available data suggest that the marine geochemistry of Cd is dominated by nutrient-like processes (i.e., required uptake). However, only one biochemical function for Cd is known: CdCA1, a Cd/Zn carbonic anhydrase from the marine diatom Thalassiosira weissflogii (9, 10). Although ubiquitous in natural waters (11), CdCA1 is absent in numerous phytoplankton including coccolithophores, cyanobacteria, archaea, and several species of diatom (11) (Table S1), and it is thus debateable whether the expression of this single enzyme can account for the nutrient-like distribution of Cd in the global ocean. Here we examine the isotopic fractionation of Cd associated with CdCA1 that has been expressed in vivo by the model microorganism, Escherichia coli. Because E. coli has no inherent use for Cd, our experimental design permits comparison of cultures both overexpressing and not expressing CdCA1 in otherwise identical experiments. Using a systematic experimental approach, we are able to identify ...

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“…Rice plants exposed to 35 Scysteine or 9 × 10 -8 M 109 Cd in solution for 24 h accumulated 109 Cd and 35 S in the same low molecular weight soluble fraction of roots (Dabin et al 1978), which might have contained phytochelatins, glutathione or other sulphur compounds complexed with Cd. Using a sensitive technique for phytochelatins, Ahner et al (1995) have shown that concentrations of Cd 2+ as low as 10 -12 M induced the synthesis of phytochelatin in several species of marine phytoplankton. In the studies of Tukendorf and Rauser (1990) and Ahner et al (1995) the binding of Cd to the phytochelatins was not demonstrated.…”

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confidence: 99%

“…Using a sensitive technique for phytochelatins, Ahner et al (1995) have shown that concentrations of Cd 2+ as low as 10 -12 M induced the synthesis of phytochelatin in several species of marine phytoplankton. In the studies of Tukendorf and Rauser (1990) and Ahner et al (1995) the binding of Cd to the phytochelatins was not demonstrated. The role of phytochelatins in the accumulation of Cd in crops exposed to low Cd levels remains to be clarified.…”

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confidence: 99%

Cadmium accumulation in crops

Grant¹,

Buckley²,

Bailey³

et al. 1998

Can. J. Plant Sci.

331

180

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Cadmium is a heavy metal present in soils from natural and anthropogenic sources. Plant uptake of Cd at levels present in the soil solution is dependent on a system that is largely metabolically mediated and competitive with the uptake system for Zn and possibly other metals. Much of the Cd taken up by plants is retained in the root, but a portion is translocated to the aerial portions of the plant and into the seed. The amount of Cd accumulated and translocated in plants varies with species and with cultivars within species. Soil, environmental and management factors impact on the amount of Cd accumulated in plants. Potential methods of reducing the accumulation of Cd in crops include reduction of Cd input to the soil system, site selection, management practices which decrease the concentration of Cd in the soil solution and its uptake and translocation by plants, and development and production of plant cultivars with the genetic tendency for low Cd uptake.

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Phytochelatin production in marine algae. 1. An interspecies comparison

Cited by 160 publications

References 19 publications

The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation

The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation

Nonspecific uptake and homeostasis drive the oceanic cadmium cycle

Cadmium accumulation in crops

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