Walid Saibi | University of Sfax (original) (raw)
Papers by Walid Saibi
Agave americana (A. americana) is a species that are considered as one of the most studied specie... more Agave americana (A. americana) is a species that are considered as one of the most studied species and there are a large number of derived products, as well as applications of agave fibers. Here, we have exploited their applied potentialities through metabolic and biochemical abilities. In this case, we monitored the presence of terpenoides, phlobatanins, tannins, anthraquinone, puerarin, apigenin, carbohydrates and vitamin C. The proteins amount was estimated to be 8.13 mg.g − 1 (FM). In addition, the A. americana leave juice enzymological characterization consists of various enzymatic activities like protease (356 U. mL − 1) and α-amylase (264 U. mL − 1). The last one (AmyAga) was purified after two purification steps, their optimal activity is showed at 70 • C and pH 9. Eventually, those findings indicate their potential use in baking industry in which AmyAga upgrades some parameter's like elasticity index, baking strength, humidity and fall time. We note also that vitamin C inhibitory capability towards some enzymes such as glucosidases that was 3 folds higher than those of exhibiting against amylases.
Exploring the Milk-Clotting Activity and Leather Industry of Agave americana Serine Protease (PAA, 2021
Proteases are hydrolytic biocatalysts that catalyze peptide linkage/cleavage reactions at the lev... more Proteases are hydrolytic biocatalysts that catalyze peptide linkage/cleavage reactions at the level of proteins and peptides with different degrees of specificity. The serine proteases are the most commercially available enzyme in the world market and are researched for their industrial uses. We report here the extraction, the biochemical characterization of a novel serine protease with milk-clotting and Leather activities (named PAA) from Agave americana. Indeed, PAA was purified at homogeneity after three purification steps involving ammonium sulfate precipitation at 80%, ethanol fractionation and finally, gel filtration coupled to HPLC system. Their optimal activity was showed at 60°C and 7.8 units of pH. PAA has an apparent molecular weight of approximately 35 kDa estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and size exclusion chromatography. In addition, the PAA irreversible inhibition by the Diisopropyl-Fluoro-Phosphate and the Phenyl-Methyl-Sulfonyl-Fluoride proves it's belonging to the serine protease family. In another hand, the PAA autodigestion level is estimated to 20% after 30 days of self-incubation, the hydrolysis percentage of casein with PAA is about 22.9%, their efficiency in milk-clotting will lead to their plausible applied in various biotechnological tools related to agrofood industries. Also, the PAA proves an excellent capability in Leather Industry.
BioMed Research International
Apart from their significance in the protection against stress conditions, the plant cell membran... more Apart from their significance in the protection against stress conditions, the plant cell membranes are essential for proper development of the diverse surface structures formed on aerial plant organs. In addition, we signal that membrane remodeling and integrity are function of some of causal physiological and enzymological aspects such as the MDA, the ion leakage and also the monitoring of some phytozymes involved in lipid and cellulose metabolisms. Those last ones are related to the membrane structure (lipases and cellulases), that were assessed in durum wheat dehydrin transgenic context (YS, K1-K2, DH2, and DH4), proline metabolic mutant (P5CS1-4) per comparison with the wild-type plant (Wt). We report also the docking data reinforcing the fact that the membrane integrity seems to be function of causal enzymological behaviors, through the molecular dynamic investigation resulting from the dehydrin-phytozyme interactions and also from the inhibition effect of the durum wheat LTP4...
Acta Physiologiae Plantarum
Archives of Physiology and Biochemistry
Functional Plant Biology
The A20/AN1 zinc-finger domain-containing proteins of the stress-associated proteins (SAPs) famil... more The A20/AN1 zinc-finger domain-containing proteins of the stress-associated proteins (SAPs) family are fast emerging as potential candidates for biotechnological approaches to improve abiotic stress tolerance in plants. We identified LmSAP, one of the SAPs genes in Lobularia maritima (L.) Desv., a halophyte brassicaceae, through its transcript accumulation in response to salinity and ionic stresses. Sequence homology analysis revealed that LmSAP contains two conserved zinc-finger domains A20 and AN1. Phylogeny analyses showed that LmSAP exhibited high amino acid sequence identity to other plant SAPs. Heterologous expression of LmSAP in yeast increased cell tolerance to salt and osmotic stress. In addition, the overexpression of LmSAP conferred high salt and ionic tolerance to transgenic tobacco plants. Transgenic tobacco seedlings showed higher survival rates and antioxidant activities under salt and ionic stresses. Enhanced antioxidant activities paralleled lower malondialdehyde an...
Natural product research, Jan 28, 2017
Among phenolic compounds, Agave americana L. extract contained puerarin (38.4%) and p-coumaric ac... more Among phenolic compounds, Agave americana L. extract contained puerarin (38.4%) and p-coumaric acid (12.29%) (pCa). From the Lineweaver-Burk plots, pCa and puerarin demonstrated a competitive and a non competitive inhibitions towards human α-amylase activity, respectively. PCa exhibited a higher human inhibitory activity with an IC of 98.8 μM which was about 2.3 times than acarbose. Puerarin (IC = 3.87 μM) and pCa (IC = 10.16 μM) also showed an excellent inhibition for Aspergillus oryzae S2 α-amylase activity. The inhibitions of the described biocatalysts compounds towards both amylases were significantly decreased when they were pre-incubated with starch. The binding modes of these compounds were evaluated in silico. The binding efficiency order of these molecules in terms of polar contact numbers for both enzymes was in agreement with the in vitro studies. These findings provided a rational reason to establish the isolated compounds capability as therapeutic target for hyperglycae...
Journal of food science and technology, 2018
extract was analyzed by reverse phase HPLC for characterization. Among phenolic compounds identif... more extract was analyzed by reverse phase HPLC for characterization. Among phenolic compounds identified, apigenin was observed to be present. The finding showed an inhibitory effect of apigenin towards Human and S2 α-amylases. Apigenin inhibition towards Human and α-amylase activities was observed to be competitive. IC50 and % inhibition of apigenin for α-amylase were 3.98 and 1.65 fold higher than for Human α-amylase. The inhibition of the described biocatalyst activity was significantly lowered when apigenin was pre-incubated with starch. In addition to the catalytic residues, 44 amino acid residues were involved on α-amylase-apigenin interactions while only 11 amino acid residues were exposed for Human α-amylase-apigenin complex. The binding site of apigenin showed 76 polar contacts for S2 α-amylase against 44 interactions for Human α-amylase. The docking studies confirmed the mode of action of apigenin and strongly suggested a higher inhibitory activity towards fungal amylase whic...
Bioprocess and Biosystems Engineering, 2016
An extracellular β-glucosidase from Fusaruim solani cultivated on wheat bran was purified by only... more An extracellular β-glucosidase from Fusaruim solani cultivated on wheat bran was purified by only two chromatographic steps. The purified enzyme exhibited optimal temperature and pH at 60 °C and pH 5, respectively. The purified β-glucosidase behaves as a very large protein due to its high degree of glycosylation. More interestingly, the endoglycosidase H (Endo H) treatment led to 97.55% loss of its initial activity after 24 h of treatment. Besides, the addition of Tunicamycin (nucleoside antibiotic blocking the N-glycosylation first step) during the culture of the fungus affected seriously the glycosylation of the enzyme. Both treatments (endo H and Tunicamycin) strengthened the idea that the hyperglycosylation is involved in the β-glucosidase activity and thermostability. This enzyme was also shown to belong to class III of β-glucosidases (multi-specific) since it was able to act on either cellobiose, gentiobiose or sophorose which are disaccharide composed of two units of D-glucose connected by β1-4, β1-6 and β1-2 linkage, respectively. The β-glucosidase activity was strongly enhanced by ferrous ion (Fe(2+)) and high ionic strength (1 M KCl). The purified enzyme exhibited an efficient transglycosylation capacity allowing the synthesis of cellotriose and cellotetraose using cellobiose as donor.
Preparative Biochemistry and Biotechnology, 2016
Fungal β-glucosidases were extensively studied regarding their various potential biotechnology ap... more Fungal β-glucosidases were extensively studied regarding their various potential biotechnology applications. Here, we report the selection of Fusarium solani strain producing high yield of β-glucosidase activity. The effect of some factors on β-glucosidase production was studied including: Initial pH, medium composition, concentration of carbon and nitrogen sources, and particle size of raw substrates. The optimal enzyme production was obtained with 4 units of pH. The highest β-glucosidase activity was produced on 4% wheat bran (WB) as raw carbon sources, reaching 5 U/mL. A positive correlation between WB particle size and the β-glucosidase production level was settled. The last one was enhanced to 13.60 U/mL in the presence of 0.5% (w/v) of ammonium sulfate. Interestingly, the activated charcoal was used as an inexpensive reagent enabling a rapid and efficient purification prior step that improved the enzyme-specific activity. Eventually, F. solani β-glucosidase acts efficiently during the bioconversion process of oleuropein. Indeed, 82.5% of oleuropein was deglycosylated after 1 hr at 40°C. Altogether, our data showed that the β-glucosidase of F. solani has a potential application to convert oleuropein to ameliorate food quality.
Journal of Plant Physiology, 2016
In plant cells, the manganese superoxide dismutase (Mn-SOD) plays an elusive role in the response... more In plant cells, the manganese superoxide dismutase (Mn-SOD) plays an elusive role in the response to oxidative stress. In this study, we describe the isolation and functional characterization of a novel Mn-SOD from durum wheat (Triticum turgidum L. subsp. Durum), named TdMnSOD. Molecular phylogeny analysis showed that the durum TdMnSOD exhibited high amino acids sequence identity with other Mn-SOD plants. The three-dimensional structure showed that TdMnSOD forms a homotetramer and each subunit is composed of a predominantly α-helical N-terminal domain and a mixed α/β C-terminal domain. TdMnSOD gene expression analysis showed that this gene was induced by various abiotic stresses in durum wheat. The expression of TdMnSOD enhances tolerance of the transformed yeast cells to salt, osmotic, cold and H2O2-induced oxidative stresses. Moreover, the analysis of TdMnSOD transgenic Arabidopsis plants subjected to different environmental stresses revealed low H2O2 and high proline levels as compared to the wild-type plants. Compared with the non-transformed plants, an increase in the total SOD and two other antioxidant enzyme activities including catalase (CAT) and peroxidases (POD) was observed in the three transgenic lines subjected to abiotic stress. Taken together, these data provide evidence for the involvement of durum wheat TdMnSOD in tolerance to multiple abiotic stresses in crop plants.
Molecular and Genomic Perspectives, 2015
Journal of applied genetics
Comparative functional analysis of two wheat Na + /H + antiporter SOS1 promoters in Arabidopsis t... more Comparative functional analysis of two wheat Na + /H + antiporter SOS1 promoters in Arabidopsis thaliana under various stress conditions Abstract The bread wheat TaSOS1 has been previously shown to be induced by salt stress treatment. To further investigate the regulation of the TaSOS1 gene, the two geno-mic fragments Pr SOS1-AB and Pr SOS1-D have been isolated and sequenced. Pr SOS1-AB and Pr SOS1-D are the promoter regions of SOS1 alleles, which are localised on genomes A and/or B, and on genome D, respectively. Sequence analysis of these two promoters revealed the presence of cis-regulatory elements which could be required for abiotic stress and abscisic acid (ABA) responsiveness. Histochemical assays of stably trans-formed Arabidopsis T3 plants showed that Pr SOS1-AB and Pr SOS1-D are active in this heterologous system, and their activities were almost the same at early developmental stages (4-, 8-and 12-day-old transgenic Arabidopsis seedlings). Nevertheless, β-glucuronidase (G...
Planta, 2015
The wheat dehydrin (DHN-5) gives birth to salinity tolerance to transgenic Arabidopsis plants by ... more The wheat dehydrin (DHN-5) gives birth to salinity tolerance to transgenic Arabidopsis plants by the regulation of proline metabolism and the ROS scavenging system. Dehydrins (DHNs) are involved in plant abiotic stress tolerance. In this study, we reported that salt tolerance of transgenic Arabidopsis plants overexpressing durum wheat dehydrin (DHN-5) was closely related to the activation of the proline metabolism enzyme (P5CS) and some antioxidant biocatalysts. Indeed, DHN-5 improved P5CS activity in the transgenic plants generating a significant proline accumulation. Moreover, salt tolerance of Arabidopsis transgenic plants was accompanied by an excellent activation of antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD) and peroxide dismutase (POD) and generation of a lower level of hydrogen peroxide (H2O2) in leaves compared to the wild-type plants. The enzyme activities were enhanced in these transgenic plants in the presence of exogenous proline. Nevertheless, proline accumulation was slightly reduced in transgenic plants promoting chlorophyll levels. All these results suggest the crucial role of DHN-5 in response to salt stress through the activation of enzymes implicated in proline metabolism and in ROS scavenging enzymes.
Applied Biochemistry and Biotechnology, 2015
Much is now known about proline multifunctionality and metabolism; some aspects of its biological... more Much is now known about proline multifunctionality and metabolism; some aspects of its biological functions are still unclear. Here, we discuss some cases in the proline, structure, definition, metabolism, compartmentalization, accumulation, plausible functions and also its implication in homeostasis and organism physiology. Indeed, we report the role of proline in cellular homeostasis, including redox balance and energy status and their implication as biocatalyst for aldolase activity. Proline can act as a signaling molecule to modulate mitochondrial functions, influence cell proliferation or cell death, and trigger specific gene expression, which can be essential for plant recovery from stresses. Although, the regulation and the function of proline accumulation, during abiotic stresses, are not yet completely understood. The engineering of proline metabolism could lead to new opportunities to improve plant tolerance against environmental stresses. This atypical amino acid has a potential role in the toxicity during growth of some microorganism, vegetal, and mammalian species. Furthermore, we note that the purpose through the work is to provide a rich, concise, and mostly cohesive source on proline, considered as a platform and an anchor between several disciplines and biological functions.
Group-2 Late Embryogenesis Abundant (LEA) proteins, also known as dehydrins, are claimed to stabi... more Group-2 Late Embryogenesis Abundant (LEA) proteins, also known as dehydrins, are claimed to stabilize macromolecules against damage caused by freezing, dehydration, ionic or osmotic stresses. However, their precise function remains unknown. We investigated the effect of wheat dehydrin (DHN-5) protein on the activity and thermostability of two distinct enzymes, β-glucosidase (bglG) and glucose oxidase/peroxidase (GOD/POD) in vitro. The purified DHN-5 protein had the capacity to preserve and stabilize the activity of bglG subjected to heat treatment. In addition, DHN-5 stabilized oxidizing enzymes, as it improved reliability in measuring glucose concentrations with a glucose oxidase/peroxidase (GOD/POD) kit while the temperature increased from 37 to 70°C. All together the data presented provide evidence that DHN-5 is a dehydrin able to preserve enzyme activities in vitro from adverse effects induced by heating. In order to understand the molecular mechanism by which DHN-5 exerts its p...
Applied microbiology and biotechnology, 2007
The filamentous fungus Stachybotrys sp has been shown to possess a rich beta-glucosidase system c... more The filamentous fungus Stachybotrys sp has been shown to possess a rich beta-glucosidase system composed of five beta-glucosidases. One of them was already purified to homogeneity and characterized. In this work, a second beta-glucosidase was purified and characterized. The filamentous fungal A19 strain was fed-batch cultivated on cellulose, and its extracellular cellulases (mainly beta-glucosidases) were analyzed. The purified enzyme is a monomeric protein of 78 kDa molecular weight and exhibits optimal activity at pH 6.0 and at 50 degrees C. The kinetic parameters, K (m) and V (max), on para-nitro-phenyl-beta-D: -glucopyranosid (p-NPG) as a substrate were, respectively, 1.846 +/- 0.11 mM and 211 +/- 0.08 micromol min(-1) ml(-1). One interesting feature of this enzyme is its high stability in a wide range of pH from 4 to 10. Besides its aryl beta-glucosidase activity towards salicin, methylumbellypheryl-beta-D: -glucoside (MU-Glc), and p-NPG, it showed a true beta-glucosidase activ...
Agave americana (A. americana) is a species that are considered as one of the most studied specie... more Agave americana (A. americana) is a species that are considered as one of the most studied species and there are a large number of derived products, as well as applications of agave fibers. Here, we have exploited their applied potentialities through metabolic and biochemical abilities. In this case, we monitored the presence of terpenoides, phlobatanins, tannins, anthraquinone, puerarin, apigenin, carbohydrates and vitamin C. The proteins amount was estimated to be 8.13 mg.g − 1 (FM). In addition, the A. americana leave juice enzymological characterization consists of various enzymatic activities like protease (356 U. mL − 1) and α-amylase (264 U. mL − 1). The last one (AmyAga) was purified after two purification steps, their optimal activity is showed at 70 • C and pH 9. Eventually, those findings indicate their potential use in baking industry in which AmyAga upgrades some parameter's like elasticity index, baking strength, humidity and fall time. We note also that vitamin C inhibitory capability towards some enzymes such as glucosidases that was 3 folds higher than those of exhibiting against amylases.
Exploring the Milk-Clotting Activity and Leather Industry of Agave americana Serine Protease (PAA, 2021
Proteases are hydrolytic biocatalysts that catalyze peptide linkage/cleavage reactions at the lev... more Proteases are hydrolytic biocatalysts that catalyze peptide linkage/cleavage reactions at the level of proteins and peptides with different degrees of specificity. The serine proteases are the most commercially available enzyme in the world market and are researched for their industrial uses. We report here the extraction, the biochemical characterization of a novel serine protease with milk-clotting and Leather activities (named PAA) from Agave americana. Indeed, PAA was purified at homogeneity after three purification steps involving ammonium sulfate precipitation at 80%, ethanol fractionation and finally, gel filtration coupled to HPLC system. Their optimal activity was showed at 60°C and 7.8 units of pH. PAA has an apparent molecular weight of approximately 35 kDa estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and size exclusion chromatography. In addition, the PAA irreversible inhibition by the Diisopropyl-Fluoro-Phosphate and the Phenyl-Methyl-Sulfonyl-Fluoride proves it's belonging to the serine protease family. In another hand, the PAA autodigestion level is estimated to 20% after 30 days of self-incubation, the hydrolysis percentage of casein with PAA is about 22.9%, their efficiency in milk-clotting will lead to their plausible applied in various biotechnological tools related to agrofood industries. Also, the PAA proves an excellent capability in Leather Industry.
BioMed Research International
Apart from their significance in the protection against stress conditions, the plant cell membran... more Apart from their significance in the protection against stress conditions, the plant cell membranes are essential for proper development of the diverse surface structures formed on aerial plant organs. In addition, we signal that membrane remodeling and integrity are function of some of causal physiological and enzymological aspects such as the MDA, the ion leakage and also the monitoring of some phytozymes involved in lipid and cellulose metabolisms. Those last ones are related to the membrane structure (lipases and cellulases), that were assessed in durum wheat dehydrin transgenic context (YS, K1-K2, DH2, and DH4), proline metabolic mutant (P5CS1-4) per comparison with the wild-type plant (Wt). We report also the docking data reinforcing the fact that the membrane integrity seems to be function of causal enzymological behaviors, through the molecular dynamic investigation resulting from the dehydrin-phytozyme interactions and also from the inhibition effect of the durum wheat LTP4...
Acta Physiologiae Plantarum
Archives of Physiology and Biochemistry
Functional Plant Biology
The A20/AN1 zinc-finger domain-containing proteins of the stress-associated proteins (SAPs) famil... more The A20/AN1 zinc-finger domain-containing proteins of the stress-associated proteins (SAPs) family are fast emerging as potential candidates for biotechnological approaches to improve abiotic stress tolerance in plants. We identified LmSAP, one of the SAPs genes in Lobularia maritima (L.) Desv., a halophyte brassicaceae, through its transcript accumulation in response to salinity and ionic stresses. Sequence homology analysis revealed that LmSAP contains two conserved zinc-finger domains A20 and AN1. Phylogeny analyses showed that LmSAP exhibited high amino acid sequence identity to other plant SAPs. Heterologous expression of LmSAP in yeast increased cell tolerance to salt and osmotic stress. In addition, the overexpression of LmSAP conferred high salt and ionic tolerance to transgenic tobacco plants. Transgenic tobacco seedlings showed higher survival rates and antioxidant activities under salt and ionic stresses. Enhanced antioxidant activities paralleled lower malondialdehyde an...
Natural product research, Jan 28, 2017
Among phenolic compounds, Agave americana L. extract contained puerarin (38.4%) and p-coumaric ac... more Among phenolic compounds, Agave americana L. extract contained puerarin (38.4%) and p-coumaric acid (12.29%) (pCa). From the Lineweaver-Burk plots, pCa and puerarin demonstrated a competitive and a non competitive inhibitions towards human α-amylase activity, respectively. PCa exhibited a higher human inhibitory activity with an IC of 98.8 μM which was about 2.3 times than acarbose. Puerarin (IC = 3.87 μM) and pCa (IC = 10.16 μM) also showed an excellent inhibition for Aspergillus oryzae S2 α-amylase activity. The inhibitions of the described biocatalysts compounds towards both amylases were significantly decreased when they were pre-incubated with starch. The binding modes of these compounds were evaluated in silico. The binding efficiency order of these molecules in terms of polar contact numbers for both enzymes was in agreement with the in vitro studies. These findings provided a rational reason to establish the isolated compounds capability as therapeutic target for hyperglycae...
Journal of food science and technology, 2018
extract was analyzed by reverse phase HPLC for characterization. Among phenolic compounds identif... more extract was analyzed by reverse phase HPLC for characterization. Among phenolic compounds identified, apigenin was observed to be present. The finding showed an inhibitory effect of apigenin towards Human and S2 α-amylases. Apigenin inhibition towards Human and α-amylase activities was observed to be competitive. IC50 and % inhibition of apigenin for α-amylase were 3.98 and 1.65 fold higher than for Human α-amylase. The inhibition of the described biocatalyst activity was significantly lowered when apigenin was pre-incubated with starch. In addition to the catalytic residues, 44 amino acid residues were involved on α-amylase-apigenin interactions while only 11 amino acid residues were exposed for Human α-amylase-apigenin complex. The binding site of apigenin showed 76 polar contacts for S2 α-amylase against 44 interactions for Human α-amylase. The docking studies confirmed the mode of action of apigenin and strongly suggested a higher inhibitory activity towards fungal amylase whic...
Bioprocess and Biosystems Engineering, 2016
An extracellular β-glucosidase from Fusaruim solani cultivated on wheat bran was purified by only... more An extracellular β-glucosidase from Fusaruim solani cultivated on wheat bran was purified by only two chromatographic steps. The purified enzyme exhibited optimal temperature and pH at 60 °C and pH 5, respectively. The purified β-glucosidase behaves as a very large protein due to its high degree of glycosylation. More interestingly, the endoglycosidase H (Endo H) treatment led to 97.55% loss of its initial activity after 24 h of treatment. Besides, the addition of Tunicamycin (nucleoside antibiotic blocking the N-glycosylation first step) during the culture of the fungus affected seriously the glycosylation of the enzyme. Both treatments (endo H and Tunicamycin) strengthened the idea that the hyperglycosylation is involved in the β-glucosidase activity and thermostability. This enzyme was also shown to belong to class III of β-glucosidases (multi-specific) since it was able to act on either cellobiose, gentiobiose or sophorose which are disaccharide composed of two units of D-glucose connected by β1-4, β1-6 and β1-2 linkage, respectively. The β-glucosidase activity was strongly enhanced by ferrous ion (Fe(2+)) and high ionic strength (1 M KCl). The purified enzyme exhibited an efficient transglycosylation capacity allowing the synthesis of cellotriose and cellotetraose using cellobiose as donor.
Preparative Biochemistry and Biotechnology, 2016
Fungal β-glucosidases were extensively studied regarding their various potential biotechnology ap... more Fungal β-glucosidases were extensively studied regarding their various potential biotechnology applications. Here, we report the selection of Fusarium solani strain producing high yield of β-glucosidase activity. The effect of some factors on β-glucosidase production was studied including: Initial pH, medium composition, concentration of carbon and nitrogen sources, and particle size of raw substrates. The optimal enzyme production was obtained with 4 units of pH. The highest β-glucosidase activity was produced on 4% wheat bran (WB) as raw carbon sources, reaching 5 U/mL. A positive correlation between WB particle size and the β-glucosidase production level was settled. The last one was enhanced to 13.60 U/mL in the presence of 0.5% (w/v) of ammonium sulfate. Interestingly, the activated charcoal was used as an inexpensive reagent enabling a rapid and efficient purification prior step that improved the enzyme-specific activity. Eventually, F. solani β-glucosidase acts efficiently during the bioconversion process of oleuropein. Indeed, 82.5% of oleuropein was deglycosylated after 1 hr at 40°C. Altogether, our data showed that the β-glucosidase of F. solani has a potential application to convert oleuropein to ameliorate food quality.
Journal of Plant Physiology, 2016
In plant cells, the manganese superoxide dismutase (Mn-SOD) plays an elusive role in the response... more In plant cells, the manganese superoxide dismutase (Mn-SOD) plays an elusive role in the response to oxidative stress. In this study, we describe the isolation and functional characterization of a novel Mn-SOD from durum wheat (Triticum turgidum L. subsp. Durum), named TdMnSOD. Molecular phylogeny analysis showed that the durum TdMnSOD exhibited high amino acids sequence identity with other Mn-SOD plants. The three-dimensional structure showed that TdMnSOD forms a homotetramer and each subunit is composed of a predominantly α-helical N-terminal domain and a mixed α/β C-terminal domain. TdMnSOD gene expression analysis showed that this gene was induced by various abiotic stresses in durum wheat. The expression of TdMnSOD enhances tolerance of the transformed yeast cells to salt, osmotic, cold and H2O2-induced oxidative stresses. Moreover, the analysis of TdMnSOD transgenic Arabidopsis plants subjected to different environmental stresses revealed low H2O2 and high proline levels as compared to the wild-type plants. Compared with the non-transformed plants, an increase in the total SOD and two other antioxidant enzyme activities including catalase (CAT) and peroxidases (POD) was observed in the three transgenic lines subjected to abiotic stress. Taken together, these data provide evidence for the involvement of durum wheat TdMnSOD in tolerance to multiple abiotic stresses in crop plants.
Molecular and Genomic Perspectives, 2015
Journal of applied genetics
Comparative functional analysis of two wheat Na + /H + antiporter SOS1 promoters in Arabidopsis t... more Comparative functional analysis of two wheat Na + /H + antiporter SOS1 promoters in Arabidopsis thaliana under various stress conditions Abstract The bread wheat TaSOS1 has been previously shown to be induced by salt stress treatment. To further investigate the regulation of the TaSOS1 gene, the two geno-mic fragments Pr SOS1-AB and Pr SOS1-D have been isolated and sequenced. Pr SOS1-AB and Pr SOS1-D are the promoter regions of SOS1 alleles, which are localised on genomes A and/or B, and on genome D, respectively. Sequence analysis of these two promoters revealed the presence of cis-regulatory elements which could be required for abiotic stress and abscisic acid (ABA) responsiveness. Histochemical assays of stably trans-formed Arabidopsis T3 plants showed that Pr SOS1-AB and Pr SOS1-D are active in this heterologous system, and their activities were almost the same at early developmental stages (4-, 8-and 12-day-old transgenic Arabidopsis seedlings). Nevertheless, β-glucuronidase (G...
Planta, 2015
The wheat dehydrin (DHN-5) gives birth to salinity tolerance to transgenic Arabidopsis plants by ... more The wheat dehydrin (DHN-5) gives birth to salinity tolerance to transgenic Arabidopsis plants by the regulation of proline metabolism and the ROS scavenging system. Dehydrins (DHNs) are involved in plant abiotic stress tolerance. In this study, we reported that salt tolerance of transgenic Arabidopsis plants overexpressing durum wheat dehydrin (DHN-5) was closely related to the activation of the proline metabolism enzyme (P5CS) and some antioxidant biocatalysts. Indeed, DHN-5 improved P5CS activity in the transgenic plants generating a significant proline accumulation. Moreover, salt tolerance of Arabidopsis transgenic plants was accompanied by an excellent activation of antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD) and peroxide dismutase (POD) and generation of a lower level of hydrogen peroxide (H2O2) in leaves compared to the wild-type plants. The enzyme activities were enhanced in these transgenic plants in the presence of exogenous proline. Nevertheless, proline accumulation was slightly reduced in transgenic plants promoting chlorophyll levels. All these results suggest the crucial role of DHN-5 in response to salt stress through the activation of enzymes implicated in proline metabolism and in ROS scavenging enzymes.
Applied Biochemistry and Biotechnology, 2015
Much is now known about proline multifunctionality and metabolism; some aspects of its biological... more Much is now known about proline multifunctionality and metabolism; some aspects of its biological functions are still unclear. Here, we discuss some cases in the proline, structure, definition, metabolism, compartmentalization, accumulation, plausible functions and also its implication in homeostasis and organism physiology. Indeed, we report the role of proline in cellular homeostasis, including redox balance and energy status and their implication as biocatalyst for aldolase activity. Proline can act as a signaling molecule to modulate mitochondrial functions, influence cell proliferation or cell death, and trigger specific gene expression, which can be essential for plant recovery from stresses. Although, the regulation and the function of proline accumulation, during abiotic stresses, are not yet completely understood. The engineering of proline metabolism could lead to new opportunities to improve plant tolerance against environmental stresses. This atypical amino acid has a potential role in the toxicity during growth of some microorganism, vegetal, and mammalian species. Furthermore, we note that the purpose through the work is to provide a rich, concise, and mostly cohesive source on proline, considered as a platform and an anchor between several disciplines and biological functions.
Group-2 Late Embryogenesis Abundant (LEA) proteins, also known as dehydrins, are claimed to stabi... more Group-2 Late Embryogenesis Abundant (LEA) proteins, also known as dehydrins, are claimed to stabilize macromolecules against damage caused by freezing, dehydration, ionic or osmotic stresses. However, their precise function remains unknown. We investigated the effect of wheat dehydrin (DHN-5) protein on the activity and thermostability of two distinct enzymes, β-glucosidase (bglG) and glucose oxidase/peroxidase (GOD/POD) in vitro. The purified DHN-5 protein had the capacity to preserve and stabilize the activity of bglG subjected to heat treatment. In addition, DHN-5 stabilized oxidizing enzymes, as it improved reliability in measuring glucose concentrations with a glucose oxidase/peroxidase (GOD/POD) kit while the temperature increased from 37 to 70°C. All together the data presented provide evidence that DHN-5 is a dehydrin able to preserve enzyme activities in vitro from adverse effects induced by heating. In order to understand the molecular mechanism by which DHN-5 exerts its p...
Applied microbiology and biotechnology, 2007
The filamentous fungus Stachybotrys sp has been shown to possess a rich beta-glucosidase system c... more The filamentous fungus Stachybotrys sp has been shown to possess a rich beta-glucosidase system composed of five beta-glucosidases. One of them was already purified to homogeneity and characterized. In this work, a second beta-glucosidase was purified and characterized. The filamentous fungal A19 strain was fed-batch cultivated on cellulose, and its extracellular cellulases (mainly beta-glucosidases) were analyzed. The purified enzyme is a monomeric protein of 78 kDa molecular weight and exhibits optimal activity at pH 6.0 and at 50 degrees C. The kinetic parameters, K (m) and V (max), on para-nitro-phenyl-beta-D: -glucopyranosid (p-NPG) as a substrate were, respectively, 1.846 +/- 0.11 mM and 211 +/- 0.08 micromol min(-1) ml(-1). One interesting feature of this enzyme is its high stability in a wide range of pH from 4 to 10. Besides its aryl beta-glucosidase activity towards salicin, methylumbellypheryl-beta-D: -glucoside (MU-Glc), and p-NPG, it showed a true beta-glucosidase activ...