Papers by Emmanouil Flemetakis
Microorganisms, May 3, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
PLOS ONE, Jan 14, 2021
Quantitative real-time reverse transcription PCR (RT-qPCR) is a highly sensitive technique that c... more Quantitative real-time reverse transcription PCR (RT-qPCR) is a highly sensitive technique that can be applied to analyze how genes are modulated by culture conditions, but identification of appropriate reference genes for normalization is a critical factor to be considered. For this reason, the expression stability of 18 candidate reference genes was evaluated for the green microalgae Tetraselmis chui using the widely employed algorithms geNorm, NormFinder, BestKeeper, the comparative ΔCT method, and RefFinder. Microalgae samples were collected from large scale outdoor photobioreactors during the growing phase (OUT_GP), and during the semi-continuous phase at different times of the day (OUT_DC). Samples from standard indoor cultures under highly controlled conditions (IND) were also collected to complement the other data. Different rankings for the candidate reference genes were obtained depending on the culture conditions and the algorithm employed. After comparison of the achieved ranks with the different methods, the references genes selected for samples from specific culture conditions were ALD and EFL in OUT_GP, RPL32 and UBCE in OUT_DC, and cdkA and UBCE in IND. Moreover, the genes EFL and cdkA or EFL and UBCE appeared as appropriate combinations for pools generated from all samples (ALL). Examination in the OUT_DC cultures of genes encoding the large and small subunits of ADP-glucose pyrophosphorylase (AGPL and AGPS, respectively) confirmed the reliability of the identified reference genes, RPL32 and UBCE. The present study represents a useful contribution for studies of gene expression in T. chui, and also represents the first step to set-up an RT-qPCR platform for quality control of T. chui biomass production in industrial facilities.
Aquaculture and Fisheries
International Journal of Molecular Sciences, May 3, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Biological Macromolecules, 2017
The plant tau class glutathione transferases (GSTs) perform diverse catalytic as well as non-cata... more The plant tau class glutathione transferases (GSTs) perform diverse catalytic as well as non-catalytic roles in detoxification of xenobiotics, prevention of oxidative damage and endogenous metabolism. In the present work, the tau class isoenzyme GSTU2-2 from Glycine max (GmGSTU2-2) was characterized. Gene expression analysis of GmGSTU2 suggested a highly specific and selective induction pattern to osmotic stresses, indicating that gene expression is controlled by a specific mechanism. Purified, recombinant GmGSTU2-2 was shown to exhibit wide-range specificity towards xenobiotic compounds and ligand-binding properties, suggesting that the isoenzyme could provide catalytic flexibility in numerous metabolic conditions. Homology modeling and phylogenetic analysis suggested that the catalytic and ligand binding sites of GmGSTU2-2 are well conserved compared to other tau class GSTs. Structural analysis identified key amino acid residues in the hydrophobic binding site and provided insights into the substrate specificity of this enzyme. The results established that GmGSTU2-2 participates in a broad network of catalytic and regulatory functions involved in the plant stress response.
Biochemical Engineering Journal, Feb 1, 2023
Plant Molecular Biology, Sep 10, 2008
Plant ammonium transporters of the AMT1 family are involved in N-uptake from the soil and ammoniu... more Plant ammonium transporters of the AMT1 family are involved in N-uptake from the soil and ammonium transport, and recycling within the plant. Although AMT1 genes are known to be expressed in nitrogen-fixing nodules of legumes, their precise roles in this specialized organ remain unknown. We have taken a reverse-genetic approach to decipher the physiological role of LjAMT1;1 in Lotus japonicus nodules. LjAMT1;1 is normally expressed in both the infected zone and the vascular tissue of Lotus nodules. Inhibition of LjAMT1;1 gene expression, using an antisense gene construct driven by a leghemoglobin promoter resulted in a substantial reduction of LjAMT1;1 transcript in the infected tissue but not the vascular bundles of transgenic plants. As a result, the nitrogen-fixing activity of nodules was partially impaired and nodule number increased compared to control plants. Expression of LjAMT1;1-GFP fusion protein in plant cells indicated a plasma-membrane location for the LjAMT1;1 protein. Taken together, the results are consistent with a role of LjAMT1;1 in retaining ammonium derived from symbiotic nitrogen fixation in plant cells prior to its assimilation.
Livestock Science, Mar 1, 2015
Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large num... more Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under-and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β-(1,4) galactosyltransferase: β-(1,4) GAT1, β-(1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous subgroups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β-(1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under-and over-fed sheep was found. Additionally, a trend of reduction on β-(1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β-(1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β-(1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.
Journal of Animal Physiology and Animal Nutrition, Nov 28, 2015
Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large num... more Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under-and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β-(1,4) galactosyltransferase: β-(1,4) GAT1, β-(1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous subgroups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β-(1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under-and over-fed sheep was found. Additionally, a trend of reduction on β-(1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β-(1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β-(1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.
Journal of Dairy Research, Feb 1, 2015
Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large num... more Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under-and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β-(1,4) galactosyltransferase: β-(1,4) GAT1, β-(1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous subgroups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β-(1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under-and over-fed sheep was found. Additionally, a trend of reduction on β-(1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β-(1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β-(1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.
Environment International, Aug 1, 2023
Trends in Plant Science, Jul 1, 2023
Social Science Research Network, 2022
Nova Science Publishers eBooks, 2013
ABSTRACT Glutathione and programmed cell death in Kluyveromyces lactis.
Animal Production Science, 2017
Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large num... more Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under-and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β-(1,4) galactosyltransferase: β-(1,4) GAT1, β-(1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous subgroups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β-(1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under-and over-fed sheep was found. Additionally, a trend of reduction on β-(1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β-(1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β-(1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.
Journal of Dairy Research, Feb 23, 2015
Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large num... more Glucose utilisation for lactose synthesis in the mammary gland involves expression of a large number of genes whose nutritional regulation remains poorly defined. In this study, the effect of long term under-and over-feeding on the expression of genes [glucose transporter 1: GLUT1, glucose transporter 3: GLUT3, Sodium glucose contransporter 1: SGLT1, two isoforms of β-(1,4) galactosyltransferase: β-(1,4) GAT1, β-(1,4) GAT3 and α-lactalbumin: LALBA] related to glucose metabolism in sheep mammary tissue (MT) was examined. Twenty-four lactating dairy sheep were divided into three homogenous subgroups and fed the same ration in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant reduction on mRNA of GLUT1 and LALBA gene in the MT of underfed sheep, compared with the respective controls and overfed and a significant reduction on mRNA level of SGLT1 and β-(1,4) GAT1 in the MT of underfed sheep, compared with the overfed ones. A significant increase in the GLUT3 mRNA accumulation in the MT of both under-and over-fed sheep was found. Additionally, a trend of reduction on β-(1,4) GAT3 mRNA level in the MT of the underfed sheep, compared with the overfed, was observed. A close positive relationship was obtained between the mRNA transcripts accumulation of GLUT1, SGLT1, β-(1,4) GAT1 and LALBA gene with the milk lactose content and milk lactose yield respectively. In conclusion, feeding level and consequently nutrient availability, may affect glucose uptake and utilisation in sheep MT by altering the GLUT1, GLUT3, SGLT1, β-(1,4) GAT1 and LALBA gene expression involved in their metabolic pathways.
Molecular Membrane Biology, 2011
Polyols are compounds that play various physiological roles in plants. Here we present the identi... more Polyols are compounds that play various physiological roles in plants. Here we present the identification of four cDNA clones of the model legume Lotus japonicus, encoding proteins of the monosaccharide transporter-like (MST) superfamily that share significant homology with previously characterized polyol transporters (PLTs). One of the transporters, named LjPLT4, was characterized functionally after expression in yeast. Transport assays revealed that LjPLT4 is a xylitol-specific H(+)-symporter (K (m), 0.34 mM). In contrast to the previously characterized homologues, LjPLT4 was unable to transport other polyols, including mannitol, sorbitol, myo-inositol and galactitol, or any of the monosaccharides tested. Interestingly, some monosaccharides, including fructose and xylose, inhibited xylitol uptake, although no significant uptake of these compounds was detected in the LjPLT4 transformed yeast cells, suggesting interactions with the xylitol binding site. Subcellular localization of LjPLT4-eYFP fusions expressed in Arabidopsis leaf epidermal cells indicated that LjPLT4 is localized in the plasma membrane. Real-time RT-PCR revealed that LjPLT4 is expressed in all major plant organs, with maximum transcript accumulation in leaves correlating with maximum xylitol levels there, as determined by GC-MS. Thus, LjPLT4 is the first plasma membrane xylitol-specific H(+)-symporter to be characterized in plants.
Journal of Animal Physiology and Animal Nutrition, May 17, 2016
Microalgae might be considered as an alternative source of fat and/or protein for ruminant&am... more Microalgae might be considered as an alternative source of fat and/or protein for ruminant's diets. However, changes in populations of ruminal micro-organisms associated with biohydrogenation process, methane and ammonia production in response to microalgae dietary supplementation have not been well characterized. Thus, 16 cross-bred goats were divided into two groups. Each goat of both groups was fed individually with alfalfa hay and concentrates separately. The concentrates of the control group had no microalgae while those of the treated group were supplemented with 10 g lyophilized Chlorella vulgaris/kg concentrate (chlor). On the 30th experimental day, samples of rumen fluid were collected for microbial DNA extraction, fatty acid profile and enzyme activity analyses. The results showed that the chlor diet compared with the control increased significantly the populations of Methanosphaera stadtmanae, Methanobrevibacter ruminantium and Methanogens bacteria and protozoa in the rumen of goats. A significant reduction in the cellulase activity and in the abundance of Ruminococcus albus, and a significant increase in the protease activity and in the abundance of Clostridium sticklandii in the rumen liquid of goats fed with the chlor diet, compared with the control, were found. Chlorella vulgaris supplementation promoted the formation of trans C18:1 , trans-11 C18:1 and monounsaturated fatty acids (MUFA), while the proportions of C18:0 and long-chain fatty acids (LCFA) reduced significantly in the rumen liquid of goats. This shift in ruminal biohydrogenation pathway was accompanied by a significant increase in Butyrivibrio fibrisolvens trans C18:1 -producing bacteria. In conclusion, the supplementation of diets with microalgae needs further investigation because it enhances the populations of methane-producing bacteria and protozoa.
Journal of Experimental Botany, Nov 16, 2005
Polyamines are considered to participate in various processes of plant development. In this study... more Polyamines are considered to participate in various processes of plant development. In this study, the possible implication of putrescine catabolism by the copper-containing amine oxidases (CuAOs, EC 1.4.3.6) in the development of roots and hypocotyls was examined. For this purpose, two cDNA clones of Glycine max (L.) Merr. cv. Williams, designated as GmCuAO1 and GmCuAO2, exhibiting extensive similarity with previously characterized CuAO clones from other plants, have been isolated and characterized. The expression of the GmCuAO1 gene is root-and hypocotyl-specific, while GmCuAO2 seems not to be expressed in a tissue-specific manner. Moreover, the GmCuAO1 gene is predominantly expressed in tissues which are characterized by rapid extension growth, such as the apical segments of etiolated hypocotyls. Using convex and concave segments of the etiolated hypocotyl apical hook it has been demonstrated that GmCuAO1 is strongly expressed in expanding cells of the concave part when exposed to light, while the same pattern is also followed by the activity of enzymes involved in putrescine catabolism. In dark and photoperiodically grown hypocotyls, activity measurements of the enzymes involved in putrescine catabolism have shown that the activity of these enzymes is several-fold higher in rapidly growing tissues. Furthermore, the cellular and tissue distribution of GmCuAO1 gene transcripts in the root axis and in hypocotyls confirmed their abundance in developing tissues and expanding cells. The results provide evidence suggesting that a tissue-specific gene coding for CuAO is correlated with cell expansion in fast-growing tissues of root and hypocotyls.
Applied Microbiology and Biotechnology
The biology and biotechnology of bacteriophages have been extensively studied in recent years to ... more The biology and biotechnology of bacteriophages have been extensively studied in recent years to explore new and environmentally friendly methods of controlling phytopathogenic bacteria. Pseudomonas syringae pv. tomato (Pst) is responsible for bacterial speck disease in tomato plants, leading to decreased yield. Disease management strategies rely on the use of copper-based pesticides. The biological control of Pst with the use of bacteriophages could be an alternative environmentally friendly approach to diminish the detrimental effects of Pst in tomato cultivations. The lytic efficacy of bacteriophages can be used in biocontrol-based disease management strategies. Here, we report the isolation and complete characterization of a bacteriophage, named Medea1, which was also tested in planta against Pst, under greenhouse conditions. The application of Medea1 as a root drenching inoculum or foliar spraying reduced 2.5- and fourfold on average, respectively, Pst symptoms in tomato plants...
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Papers by Emmanouil Flemetakis