Insertional Mutagenesis in a Homologue of a Pi Transporter Gene Confers Arsenate Resistance on Chlamydomonas

Kobayashi, Isao; Fujiwara, Shoko; Shimogawara, Kosuke; Kaise, Toshikazu; Usuda, Hideaki; Tsuzuki, Mikio

doi:10.1093/pcp/pcg081

Cited by 23 publications

(19 citation statements)

References 36 publications

(42 reference statements)

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“…Interestingly, PTB2-PTB3 and PTB5-PTB4 are contiguous, with the transcript from the proximal gene of each pair (PTB2 and PTB5) being most strongly elevated after 24 h of P starvation. No significant increase in the level of PTB1 mRNA was observed during P stress, which is in agreement with the report of Kobayashi et al (24), and the PTB6 transcript could not be detected (data not shown).…”

Section: Resultssupporting

confidence: 93%

“…Congruent with this result, the PTB1 transcript level does not respond significantly to P deprivation conditions. Kobayashi et al (24) have suggested that PTB1 may be involved in intracellular P i transport.…”

Section: Discussionmentioning

confidence: 99%

“…The incorporation of Cy3-dUTP and Cy5-dUTP (Amersham Pharmacia Biotech, Piscataway, NJ) was performed as described by Zhang et al (56), with the following modifications: (i) 200 to 500 ng of poly(A) RNA was used as the template for labeling reactions; (ii) the deoxynucleoside triphosphate mixture contained 1 mM dTTP and 2.5 mM (each) of dATP, dCTP, and dGTP; (iii) labeling reactions were incubated at 42°C for 30 min, 45°C for 20 min, and 50°C for 30 min; (iv) incorporation of the fluorescent dyes into cDNA was not examined; (v) the reference RNA was isolated from log-phase cells of wild-type strain CC-125 prior to P deprivation; and (vi) samples prepared from P-starved (4,12,24, and 48 h) CC-125 and P-replete (0 h) and P-starved (4,12,24, and 48 h) psr1-1 cells were compared to the reference sample.…”

Section: Methodsmentioning

confidence: 99%

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Genome-Based Approaches to Understanding Phosphorus Deprivation Responses and PSR1 Control in Chlamydomonas reinhardtii

2006

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The Chlamydomonas reinhardtii transcription factor PSR1 is required for the control of activities involved in scavenging phosphate from the environment during periods of phosphorus limitation. Increased scavenging activity reflects the development of high-affinity phosphate transport and the expression of extracellular phosphatases that can cleave phosphate from organic compounds in the environment. A comparison of gene expression patterns using microarray analyses and quantitative PCRs with wild-type and psr1 mutant cells deprived of phosphorus has revealed that PSR1 also controls genes encoding proteins with potential "electron valve" functions-these proteins can serve as alternative electron acceptors that help prevent photodamage caused by overexcitation of the photosynthetic electron transport system. In accordance with this finding, phosphorus-starved psr1 mutants die when subjected to elevated light intensities; at these intensities, the wild-type cells still exhibit rapid growth. Acclimation to phosphorus deprivation also involves a reduction in the levels of transcripts encoding proteins involved in photosynthesis and both cytoplasmic and chloroplast translation as well as an increase in the levels of transcripts encoding stress-associated chaperones and proteases. Surprisingly, phosphorus-deficient psr1 cells (but not wild-type cells) also display expression patterns associated with specific responses to sulfur deprivation, suggesting a hitherto unsuspected link between the signal transduction pathways involved in controlling phosphorus and sulfur starvation responses.Together, these results demonstrate that PSR1 is critical for the survival of cells under conditions of suboptimal phosphorus availability and that it plays a key role in controlling both scavenging responses and the ability of the cell to manage excess absorbed excitation energy.

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Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Genome-Based Approaches to Understanding Phosphorus Deprivation Responses and PSR1 Control in Chlamydomonas reinhardtii

2006

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“…As a relatively rapid, reversible process, adsorption plays an important role in the As detoxification in a wide variety of microalgal species (Jiang et al 2011;Kobayashi et al 2003;Morelli et al 2005;Olguín and Sánchez-Galván 2012;PawlikSkowronska et al 2004). It also holds promise for its potential applications for bioremediation of As in the water environment because it is considered to be a clean technology (Brinza et al 2007) and the As adsorption could reach 60 % of total amount of this element in microalgae (Wang et al 2013c;Zhang et al 2013a).…”

Section: Arsenic Adsorption On Algal Cell Surfacementioning

confidence: 99%

Review of arsenic speciation, toxicity and metabolism in microalgae

Wang

et al. 2015

Rev Environ Sci Biotechnol

165

100

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Arsenic is a toxic metalloid and its pollution has become a global environmental problem. This paper reviewed the current knowledge on the speciation, toxicity and metabolism of arsenic in microalgae. A number of arsenic species are present in various microalgae. Due to the great toxicity of inorganic arsenic, microalgae may undergo different processes to reduce the arsenic toxicity, including cell surface binding, arsenite [As(III)] oxidation, arsenate [As(V)] reduction, methylation, transformation into arsenosugars or arsenolipids, chelation of As(III) with glutathione and phytochelatins, as well as excretion from cells. Several genes and enzymes involved in arsenic transformations have been identified and characterized. Many factors, especially nutrient elements (e.g., nitrogen and phosphorus) in cells and in culture, affect arsenic metabolic pathways of microalgae. Arsenic metabolism in the unicellular algae has gained considerable interest because these processes control not only the effectiveness of arsenic phycoremediation, but also the risk of arsenic contamination in algal products. Future research need to focus on (1) the regulative mechanisms of arsenic absorption, biotransformation and excretion at molecular level; (2) the effects of intracellular nutrient dynamics on arsenic speciation; (3) the impacts of culture regime on the arsenic metabolism in microalgae; (4) the transfer of arsenic species across aquatic food web in order to better evaluate the roles of microalgae in arsenic cycling.

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“…P-starved cells also conserve Pi by inhibiting the turnover of chloroplast transcripts by the phosphorylytic chloroplast polynucleotide phosphorylase (Yehudai-Resheff et al 2007). Like Sdeprivation responses, P deficiency-specific responses are often regulated at the level of gene expression, as transcripts encoding extracellular phosphatases and Pi transporters increase markedly in abundance following elimination of P from the growth medium (Kobayashi et al 2003;Chang et al 2005;Moseley et al 2006).…”

Section: àmentioning

confidence: 99%

Genetic Interactions Between Regulators of Chlamydomonas Phosphorus and Sulfur Deprivation Responses

et al. 2009

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The Chlamydomonas reinhardtii PSR1 gene is required for proper acclimation of the cells to phosphorus (P) deficiency. P-starved psr1 mutants show signs of secondary sulfur (S) starvation, exemplified by the synthesis of extracellular arylsulfatase and the accumulation of transcripts encoding proteins involved in S scavenging and assimilation. Epistasis analysis reveals that induction of the S-starvation responses in P-limited psr1 cells requires the regulatory protein kinase SNRK2.1, but bypasses the membrane-targeted activator, SAC1. The inhibitory kinase SNRK2.2 is necessary for repression of S-starvation responses during both nutrient-replete growth and P limitation; arylsulfatase activity and S deficiency-responsive genes are partially induced in the P-deficient snrk2.2 mutants and become fully activated in the P-deficient psr1snrk2.2 double mutant. During P starvation, the sac1snrk2.2 double mutants or the psr1sac1snrk2.2 triple mutants exhibit reduced arylsulfatase activity compared to snrk2.2 or psr1snrk2.2, respectively, but the sac1 mutation has little effect on the abundance of S deficiency-responsive transcripts in these strains, suggesting a post-transcriptional role for SAC1 in elicitation of S-starvation responses. Interestingly, P-starved psr1snrk2.2 cells bleach and die more rapidly than wild-type or psr1 strains, suggesting that activation of S-starvation responses during P deprivation is deleterious to the cell. From these results we infer that (i) P-deficient growth causes some internal S limitation, but the S-deficiency responses are normally inhibited during acclimation to P deprivation; (ii) the S-deficiency responses are not completely suppressed in P-deficient psr1 cells and consequently these cells synthesize some arylsulfatase and exhibit elevated levels of transcripts for S-deprivation genes; and (iii) this increased expression is controlled by regulators that modulate transcription of S-responsive genes during S-deprivation conditions. Overall, the work strongly suggests integration of the different circuits that control nutrient-deprivation responses in Chlamydomonas.T HE elements phosphorus (P) and sulfur (S) are essential macronutrients for sustaining life. P is a structural component of nucleic acids and phospholipids, and is a ubiquitous modifier of carbohydrates and proteins, while S is incorporated into sulfolipids, polysaccharides, proteins, cofactors, and a wide variety of important metabolites including S-adenosyl-methionine, glutathione, and phytochelatins. The preferred forms of P and S that are assimilated by plants and microbes are the orthophosphate ion, PO 4 3À (Pi), and the sulfate ion, SO 4 2À

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Insertional Mutagenesis in a Homologue of a Pi Transporter Gene Confers Arsenate Resistance on Chlamydomonas

Cited by 23 publications

References 36 publications

Genome-Based Approaches to Understanding Phosphorus Deprivation Responses and PSR1 Control in Chlamydomonas reinhardtii

Genome-Based Approaches to Understanding Phosphorus Deprivation Responses and PSR1 Control in Chlamydomonas reinhardtii

Review of arsenic speciation, toxicity and metabolism in microalgae

Genetic Interactions Between Regulators of Chlamydomonas Phosphorus and Sulfur Deprivation Responses

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