E. V. Ermilova

St Petersburg University | SPBU · Faculty of Biology Science

NO is a gaseous signaling redox-active molecule that functions in various eukaryotes. However, its synthesis, turnover, and effects in cells are specific in plants in several aspects. Compared with higher plants, the role of NO in Chlorophyta has not been investigated enough. Yet, some of the mechanisms for controlling levels of this signaling mole...

N-Acetyl-L-glutamate kinase (NAGK) catalyzes the rate-limiting step in the ornithine/arginine biosynthesis pathway in eukaryotic and bacterial oxygenic phototrophs. NAGK is the most highly conserved target of the PII signal transduction protein in Cyanobacteria and Archaeplastida (red algae and Chlorophyta). However, there is still much to be learn...

N-Acetyl-L-glutamate kinase (NAGK) catalyzes the rate-limiting step in the ornithine/arginine biosynthesis pathway in eukaryotic and bacterial oxygenic phototrophs. NAGK is the most highly conserved target of the PII signal transduction protein in Cyanobacteria and Archaeplastida (red algae and Chlorophyta). However, yet there is still much to be l...

Nitric oxide (NO) acts as a key signaling molecule in higher plants, regulating many physiological processes. Several photosynthetic algae from different lineages are also known to produce NO. However, it remains unclear whether this messenger is produced by non-photosynthetic algae. Among these organisms, the colorless alga Polytomella parva is a...

Main conclusion Truncated hemoglobin 2 is involved in fine-tuning of PSR1-regulated gene expression during phosphorus deprivation. Abstract Truncated hemoglobins form a large family found in all domains of life. However, a majority of physiological functions of these proteins remain to be elucidated. In the model alga Chlamydomonas reinhardtii, ma...

Low temperature (or cold) is one of the major environmental factors that limit the growth and development of many plants. Various plant species have evolved complex mechanisms to adjust to decreased temperature. Mesophilic chlorophytes are a widely distributed group of eukaryotic photosynthetic organisms, but there is insufficient information about...

The PII superfamily consists of signal transduction proteins found in all domains of life. Canonical PII proteins sense the cellular energy state through the competitive binding of ATP and ADP, and carbon/nitrogen balance through 2‐oxoglutarate binding. The ancestor of Archaeplastida inherited its PII signal transduction protein from an ancestral c...

The PII superfamily consists of signal transduction proteins found in all domains of life. Canonical PII proteins sense the cellular energy state through the competitive binding of ATP and ADP, and carbon/nitrogen balance through 2‐oxoglutarate binding. The ancestor of Archaeplastida inherited its PII signal transduction protein from an ancestral c...

Truncated hemoglobins (trHbs) form a widely distributed family of proteins found in archaea, bacteria, and eukaryotes. Accumulating evidence suggests that trHbs may be implicated in functions other than oxygen delivery, but these roles are largely unknown. Characterization of the conditions that affect trHb expression and investigation of their reg...

Main conclusion l-Arginine supports growth and resulted in increased PII signaling protein levels and lipid droplet accumulation in the colorless green alga Polytomella parva. Abstract Polytomella parva, a model system for nonphotosynthetic green algae, utilizes ammonium and several carbon sources, including ethanol and acetate. We previously repo...

During evolution, several algae and plants became heterotrophic and lost photosynthesis; however, in most cases, a nonphotosynthetic plastid was maintained. Among these organisms, the colourless alga Polytomella parva is a special case, as its plastid is devoid of any DNA, but is maintained for specific metabolic tasks carried out by nuclear encode...

In the present work, generation of hydrogen peroxide in Chlamydomonas reinhardtii Dang. cells under hypothermia was demonstrated. Analysis in these cells of genes' transcription encoding the enzymes involved in detoxification of H2O2 in them, such as ascorbate peroxidases (APX1, APX2 and APX3), catalases (CAT1 and CAT2), and glutathione peroxidases...

Background The PII proteins constitute a large superfamily, present in all domains of life. Until now, PII proteins research in Chloroplastida (green algae and land plants) has mainly focused on post-translation regulation of these signal transductors. Emerging evidence suggests that PII level is tightly controlled with regard to the nitrogen sourc...

PII superfamily consists of widespread signal transduction proteins found in all domains of life. Whereas they are well-studied in Archaea, Bacteria and Chloroplastida, no PII homolog has been analyzed in Rhodophyta (red algae), where PII is encoded by a chloroplast localized glnB gene. Here, we characterized relevant sensory properties of PII from...

The mitochondrial respiratory chain in plants, some protists and many fungi consists of the ATP-coupling cyanide-sensitive cytochrome pathway and the cyanide-resistant alternative respiratory pathway. The alternative pathway is mediated by alternative oxidase (AOX). Although AOX has been proposed to play essential roles in nutrient stress tolerance...

The unicellular green alga Chlamydomonas reinhardtii reacts to sulfur (S) starvation with the increased expression of numerous genes. One gene which is induced in illuminated anaerobic S-deprived cells is the ferredoxin-5 gene (FDX5). To test FDX5 transcriptional regulation in aerobic cultures, we used a real-time PCR analysis and an artificial mic...

The mitochondrial respiratory chain in plants, many fungi and some protists consists of the ATP-coupling cyanide-sensitive cytochrome pathway and the cyanide-resistant alternative respiratory pathway. The alternative pathway is mediated by alternative oxidase (AOX). In unicellular algae, AOXs are monomeric fungi-type proteins. Studies performed in...

Truncated hemoglobins constitute a large family, present in bacteria, in archaea and in eukaryotes. However, a majority of physiological functions of these proteins remains to be elucidated. Identification and characterization of a novel role of truncated hemoglobins in the model alga provides a framework for a more complete understanding of their...

Effects of sulfur deprivation conditions on THB1 transcript accumulation in parental strain cw15-325 and THB1-amiRNA strains. Vegetative cells were grown in TAP medium and transferred to TAP-S medium in the light for 1h, 2h, 4h, 6h or 8h. The bars are means of the relative fold change (ΔCT) of three biological replicates obtained by real-time RT-PC...

Comparative chlorophyll contents (A), protein contents (B) and viability (C) of parental strain cw15-325 and THB1-amiRNA strains. Vegetative cells were grown in TAP medium and transferred to TAP-S medium in the light for 24h, 48h, 72h or 96h. A viability dye was used to distinguish viable from nonviable cells as explained in the Materials and Metho...

Confocal images of cell populations from the cw15-325 and amiRNA-THB1-11 strains grown in TAP (TAP), deprived of S (-S) or deprived of S in the presence of 50 μM (-S+50 μM NO) or 100 μM DEA NONOate (-S+100 μM NO). Imaging was also performed on the same starved culture supplemented with 100 μM cPTIO and 100 μM DEA NONOate (-S+100 μM NO+ cPTIO). The...

Gene expression analysis. Fig A. RNA integrity. Electrophoresis of representative RNA samples from C reinhardtii cells of cw15-325 strain grown in TAP medium and transferred to TAP-S medium in the light for 8h, 24h, 48h or 72h. Fig B. Melt curve peaks of THB1-12 and RACK1-genes obtained from qRT-PCR analysis. Cells were treated as described in lege...

The unicellular green alga Chlorella variabilis NC64A is an endosymbiont of the ciliate Paramecium bursaria. The host’s control, including the transfer of biochemical substrates from P. bursaria to C. variabilis, is involved in symbiotic relationships. C. variabilis NC64A that had been re-infected to P. bursaria for more than 1 year and isolated fr...

A feature of the mitochondrial electron transport chain in plants, some protists and many fungi is the presence of two terminal oxidases, the energy-conserving cytochrome oxidase and another termed alternative oxidase (AOX). AOX branches from the main respiratory chain, directly coupling the oxidation of ubiquinol with reduction of oxygen to water....

Although mitochondrial alternative oxidase (AOX) has been proposed to play essential roles in stress tolerance of plants, the effects of cadmium (Cd), an important environmental pollutant, on AOX are largely unknown. The green alga Chlamydomonas reinhardtii reacts to Cd stress conditions with the induced expression of many genes. In this work, we d...

The alternative oxidase (AOX) is a non-energy conserving terminal oxidase that has emerged as an important mitochondrial component of the cell stress responses. Although the most studied abiotic condition in relation to Chlamydomonas reinhardtii is high temperature, changes in AOX capacity of the alga were studied only under oxidative stress and co...

Although PII signal transduction proteins have been described in bacteria, archaea and plants, only one PII homolog has so far been characterized in green algae. Using a specific antibody to the PII protein from Chlamydomonas (CrPII), we provide the evidence that the model plant organism Chlorella variabilis NC64A (NC64A) possesses a protein that i...

Glutamine is the primary metabolite of nitrogen assimilation from inorganic nitrogen sources in microorganisms and plants. The ability to monitor cellular nitrogen status is pivotal for maintaining metabolic homeostasis and sustaining growth. The present study identifies a glutamine-sensing mechanism common in the entire plant kingdom except Brassi...

Nitrite plays an important role in the nitrogen metabolism of most cells, including Chlamydomonas reinhardtii. We have shown that vegetative cells of C. reinhardtii are attracted by nitrite. The Nia1nit2 mutant with defects in genes encoding the nitrate reductase and regulatory protein NIT2 respectively was found to exhibit normal chemotaxis to nit...

The characteristics of signal PII proteins identified in bacteria, archaea, and plants are presented. Special attention is paid to the properties and functions of PII proteins in microorganisms with oxygenic photosynthesis type: cyanobacteria and unicellular green algae. The structure and regulation of PII proteins are reviewed. The mechanisms of i...

Although PII signal transduction proteins have been described in bacteria, archaea and higher plants, no PII homolog has so far been characterized in green algae. In the unicellular green alga Chlamydomonas reinhardtii, the PII protein is encoded by a single nuclear gene CrGLB1. The C. reinhardtii PII (CrPII) was cloned and overexpressed with a C-t...

Chlamydomonas has long been one of the most successful unicellular organism for genetic and biochemical studies of the photosynthesis, organelle genomes and flagellar assembly. The availability of the new molecular genetic techniques is increasing interest in Chlamydomonas as a model system for research in areas like swimming behavior where it prev...

The unicellular green alga Chlamydomonas reinhardtii is able to take up methylammonium/ammonium from the medium at different stages of its sexual life cycle. Vegetative cells and pre-gametes mostly used a low-affinity system (LATS) component, but gametes obtained after light treatment of N-deprived pre-gametes expressed both LATS and high-affinity...

Ammonium is the preferred nitrogen source and chemoattractant for the unicellular green alga Chlamydomonas reinhardtii. Here we describe that chemotaxis to methylammonium, a non-metabolizable analogue to ammonium, that occurs only in vegetative cells and pregametes but not in gametes. A new methylammonium-resistant mutant, hat1 that was generated b...

Summary Absorption of blue light by phototropin results in the activation of signaling pathways that control the switchoff of chemotaxis during gametogenesis, the conversion of pregametes to gametes, and the maintenance of mating competence in gametes. Pregametes were treated with pharmacological compounds to test their effect on the lightinduced s...

The CALU Culture Collection of microscopic algae and other microorganisms has celebrated its 45 th year of continuous operation in 2003. Although it was originally designed to supply live material for aims of biotechnology in the former USSR, it gradually focused itself on isolation, preservation, classification, and polyphasic research with micros...

During sexual differentiation, Chlamydomonas reinhardtii changes its chemotactic behavior in response to ammonium. Just like gamete formation, the change in chemotaxis mode is controlled by the sequential action of two environmental cues, removal of ammonium or nitrate from the medium and light. Thus, vegetative cells and mating incompetent pre-gam...

Chemotactic behavior of Chlamydomonas reinhardtii is altered during the sexual life cycle. Unlike vegetative cells and noncompetent pregametes, mature gametes did not show chemotaxis to ammonium. Loss of chemotaxis to ammonium in mating-competent cells is controlled by gamete-specific genes that are common for both mating-type gametes. Change of ch...

The swimming behaviour of the green flagellated protist Chlamydomonas reinhardtii is influenced by several different external stimuli including light and chemical attractants. Common components are involved in both the photo- and chemo-sensory transduction pathways, although the nature and organisation of these pathways are poorly understood. To le...

Motile cells of unicellular green alga Chlamydomonas reinhardtii can perceive both light and chemical signals. Algal mutants with defects in the dynein arm structure (ida4 and oda22), ptx mutants deficient in the axonemal sensitivity to calcium ions, and ppr mutants lacking an ionic channel specific to the photophobic response were analyzed. The me...

Motile cells of the unicellular green alga Chlamydomonas reinhardtii manifest chemotaxis towards sucrose, maltose, xylose, and mannitol. To obtain mutants with impaired chemotaxis towards sucrose, we used the method of random insertional mutagenesis. Strain cw15arg7 was transformed with a pARG7.8 plasmid that carried the gene of C. reinhardtii argi...

The unicellular alga Chlamydomonas reinhardtii exhibits active orientation with respect to a chemical gradient. As already reported before, Chlamydomonas cells are attracted to ammonium ion and some sugars. Chemotactic orientation of C. reinhardtii is Ca2+ dependent. The Ca2+ channel blockers Cd2+, La3+, ruthenium red, verapamil and diltiazem compl...

A positive chemotaxis to sugars (maltose, sucrose, and xylose) and mannite has been studied by the capillary method in the Chlamydomonas reinhardtii strain 495 with negative phototaxis. The addition of an attractant to the suspension of mobile cells temporarily inhibited the photoresponse at a light intensity of 6 and 18 W/m2, while at 90 W/m2, no...

Zoospores of Chlamydomonas reinhardtii exhibit chemotaxis towards maltose, sucrose, xylose, mannitol, and ammonium. Ten independent mutants defective in chemotaxis towards sugars have been isolated. These mutants form five phenotypic classes. Genetic analysis of two mutant strains defective in chemotaxis to maltose (CHE1, CHE3) and two mutant strai...

Chemotaxis ofChlamydomonas reinhardtii 137c cells towards maltose and sucrose was observed by capillary assay. The threshold concentration was approximately 10-5m for maltose and 10-3m for sucrose. The peak accumulation of cells occurred at 10-3m for maltose and 10-2m for sucrose. A selection procedure for chemotaxis mutants was developed. Mutant s...

Summary Chemotactic behavior of Chlamydomonas reinhardtii is changed during gametogenesis. Vegetative cells exhibit chemotaxis to ammonium ion. In the light, nitrogen deprivation induces the differentiation of vegetative cells into gametes that are not attracted to ammonium ion. Some Lamino acids affected the conversion of vegetative cells into che...