- Botany Department, Faculty of Science, Zagazig University, Zagazig, Sharkia, Egypt
- +20 55 234 28 39
Rashad Kebeish
Zagazig University, Department of Botany, Faculty Member
- Taibah University, Madinah, Saudi Arabia, Department of Biology, Faculty Memberadd
- Motivated and active researcher with professional management skillsedit
Many plant families produce coumarin (COU) and its derivatives as secondary metabolites via the phenylpropanoid biosynthetic pathway. This ubiquitous group of phytochemicals was shown to have diverse physiological effects on cellular,... more
Many plant families produce coumarin (COU)
and its derivatives as secondary metabolites via the phenylpropanoid
biosynthetic pathway. This ubiquitous group of
phytochemicals was shown to have diverse physiological
effects on cellular, tissue, and organ levels. So far, research
dealing with the hormonal like behavior of COU and its
interaction with the activity and/or transport of phytohormones
is very limited. In the current study, the impact of
COU on redox homeostasis in aleurone layers of wheat
grains was investigated. Aleurone layers were incubated in
either 1000 μM COU or 5 μM gibberellic acid (
GA3) alone
or in combination with 5 μM abscisic acid (ABA). Results
revealed that both COU and GA3
treatments induced the
production of α-amylase but inhibited the activities of
superoxide dismutase, catalase and ascorbate peroxidase.
The downregulation of antioxidant enzymes that is provoked
by COU and GA3
was accompanied by significant
accumulation of both H2O2
and malondialdehyde. In contrast
with the effect of ABA, both COU and GA3
treatments
resulted in a significant reduction in cell viability
as revealed by trypan blue staining. These results suggest
that COU could disrupt the redox balance in aleurone layers
through downregulation of the enzymatic antioxidant system. Therefore, the current study provides evidence for
the gibberellin like activity of COU.
and its derivatives as secondary metabolites via the phenylpropanoid
biosynthetic pathway. This ubiquitous group of
phytochemicals was shown to have diverse physiological
effects on cellular, tissue, and organ levels. So far, research
dealing with the hormonal like behavior of COU and its
interaction with the activity and/or transport of phytohormones
is very limited. In the current study, the impact of
COU on redox homeostasis in aleurone layers of wheat
grains was investigated. Aleurone layers were incubated in
either 1000 μM COU or 5 μM gibberellic acid (
GA3) alone
or in combination with 5 μM abscisic acid (ABA). Results
revealed that both COU and GA3
treatments induced the
production of α-amylase but inhibited the activities of
superoxide dismutase, catalase and ascorbate peroxidase.
The downregulation of antioxidant enzymes that is provoked
by COU and GA3
was accompanied by significant
accumulation of both H2O2
and malondialdehyde. In contrast
with the effect of ABA, both COU and GA3
treatments
resulted in a significant reduction in cell viability
as revealed by trypan blue staining. These results suggest
that COU could disrupt the redox balance in aleurone layers
through downregulation of the enzymatic antioxidant system. Therefore, the current study provides evidence for
the gibberellin like activity of COU.
Research Interests:
Cyanate and its derivatives are considered as environmental hazardous materials. Cyanate is released to the environment through many chemical industries and mining wastewater. Cyanase enzyme converts cyanate into CO2 and NH3 in a... more
Cyanate and its derivatives are considered as environmental
hazardous materials. Cyanate is released to the environment
through many chemical industries and mining
wastewater. Cyanase enzyme converts cyanate into CO2 and
NH3 in a bicarbonate-dependent reaction. At low cyanate concentrations,
the endogenous plant cyanases play a vital role in
cyanate detoxification. However, such cyanate biodegradation
system is probably insufficient due to the excess cyanate concentrations
at contaminated sites. In this study, we have transferred
the activity of the cyanobacterial cyanase into
Arabidopsis thaliana plants in order to enhance plant resistance
against cyanate toxicity. The enzyme was shown to be
active in planta. Transgenic plants exposed to cyanate, either
applied by foliar spray or supplemented in growth medium,
showed less reduction in pigment contents, antioxidant enzymes,
carbohydrate contents, and reduced levels of plant
growth retardation. Plant growth assays under cyanate stress
showed enhanced growth and biomass accumulation in
cyanase overexpressors compared to control plants. Results
of this study provide evidence for developing novel ecofriendly
phytoremediation systems for cyanate detoxification.
hazardous materials. Cyanate is released to the environment
through many chemical industries and mining
wastewater. Cyanase enzyme converts cyanate into CO2 and
NH3 in a bicarbonate-dependent reaction. At low cyanate concentrations,
the endogenous plant cyanases play a vital role in
cyanate detoxification. However, such cyanate biodegradation
system is probably insufficient due to the excess cyanate concentrations
at contaminated sites. In this study, we have transferred
the activity of the cyanobacterial cyanase into
Arabidopsis thaliana plants in order to enhance plant resistance
against cyanate toxicity. The enzyme was shown to be
active in planta. Transgenic plants exposed to cyanate, either
applied by foliar spray or supplemented in growth medium,
showed less reduction in pigment contents, antioxidant enzymes,
carbohydrate contents, and reduced levels of plant
growth retardation. Plant growth assays under cyanate stress
showed enhanced growth and biomass accumulation in
cyanase overexpressors compared to control plants. Results
of this study provide evidence for developing novel ecofriendly
phytoremediation systems for cyanate detoxification.
Research Interests:
Lasparaginase (EC 3.5.1.1), which catalyzes the deamidation of Lasparagine to Laspartic acid and ammonia, has been widely used as a key therapeutic tool in the treatment of tumors. The current commercially available Lasparaginases,... more
Lasparaginase (EC 3.5.1.1), which catalyzes the deamidation of Lasparagine to Laspartic acid and ammonia, has been widely used as a key therapeutic tool in the treatment of tumors. The current commercially available Lasparaginases, produced from bacteria, have signs of toxicity and hypersensitivity reactions during the course of tumor therapy. Therefore, searching for Lasparaginases with unique biochemical properties and fewer adverse effects was the objective of this work. In this study, cyanobacterial strain Synechococcus elongatus PCC6803 was found as a novel source of Lasparaginase. The Lasparaginase gene coding sequence (gi:939195038) was cloned and expressed in E. coli BL21(DE3), and the recombinant protein (Se.ASPII) was purified by affinity chromatography. The enzyme has high affinity towards L asparagine and shows very weak affinity towards Lglutamine. The enzymatic properties of the recombinant enzyme were investigated, and the kinetic parameters (Km, Vmax) were measured. The pH and temperature dependence profiles of the novel enzyme were analyzed. The work was extended to measure the antitumor properties of the novel enzyme against different human tumor cell lines.
Research Interests:
Research Interests:
Photosynthetic capacity is a promising target for metabolic engineering of crop plants towards higher productivity. Crop photosynthesis is limited by multiple factors dependent on the environmental conditions. This includes photosynthetic... more
Photosynthetic capacity is a promising target for metabolic engineering of crop plants towards higher productivity. Crop photosynthesis is limited by multiple factors dependent on the environmental conditions. This includes photosynthetic electron transport, regeneration of CO2 acceptor molecules in the reductive pentose phosphate cycle, the activity and substrate specificity of the CO2-fixing enzyme Ribulose-1,5-bisphosphate carboxylase/oxygenase, and the associated flow through the photorespiratory pathway. All these aspects of the photosynthetic network have been the subject of recently published metabolic engineering approaches in model species. Together, the novel results raise hopes that engineering of photosynthesis in crop species can significantly increase agricultural productivity.
Research Interests:
The major photorespiratory pathway in higher plants is distributed over chloroplasts, mitochondria, and peroxisomes. In this pathway, glycolate oxidation takes place in peroxisomes. It was previously suggested that a mitochondrial... more
The major photorespiratory pathway in higher plants is distributed over chloroplasts, mitochondria, and peroxisomes. In this pathway, glycolate oxidation takes place in peroxisomes. It was previously suggested that a mitochondrial glycolate dehydrogenase (GlcDH) that was conserved from green algae lacking leaf-type peroxisomes contributes to photorespiration in Arabidopsis thaliana. Here, the identification of two Arabidopsis mitochondrial alanine:glyoxylate aminotransferases (ALAATs) that link glycolate oxidation to glycine formation are described. By this reaction, the mitochondrial side pathway produces glycine from glyoxylate that can be used in the glycine decarboxylase (GCD) reaction of the major pathway. RNA interference (RNAi) suppression of mitochondrial ALAAT did not result in major changes in metabolite pools under standard conditions or enhanced photorespiratroy flux, respectively. However, RNAi lines showed reduced photorespiratory CO(2) release and a lower CO(2) compen...
Research Interests:
Research Interests:
... The phenomenon of photorespiration was first described by Decker and Tio in 1959 who observed, in the course of photosynthetic gas ... During both carboxylation and oxygénation cat alysed by RuBisCO cleavage of RuBP occurs between... more
... The phenomenon of photorespiration was first described by Decker and Tio in 1959 who observed, in the course of photosynthetic gas ... During both carboxylation and oxygénation cat alysed by RuBisCO cleavage of RuBP occurs between carbon atoms 2 and 3 (figure 4). There ...
Research Interests:
Micropropagation and development of transgenic callus of Daucus glaber forssk expressing the PYS (Phytoene Synthase gene)
We introduced the Escherichia coli glycolate catabolic pathway into Arabidopsis thaliana chloroplasts to reduce the loss of fixed carbon and nitrogen that occurs in C3 plants when phosphoglycolate, an inevitable by-product of... more
We introduced the Escherichia coli glycolate catabolic pathway into Arabidopsis thaliana chloroplasts to reduce the loss of fixed
carbon and nitrogen that occurs in C3 plants when phosphoglycolate, an inevitable by-product of photosynthesis, is recycled
by photorespiration. Using step-wise nuclear transformation with five chloroplast-targeted bacterial genes encoding glycolate
dehydrogenase, glyoxylate carboligase and tartronic semialdehyde reductase, we generated plants in which chloroplastic
glycolate is converted directly to glycerate. This reduces, but does not eliminate, flux of photorespiratory metabolites through
peroxisomes and mitochondria. Transgenic plants grew faster, produced more shoot and root biomass, and contained more
soluble sugars, reflecting reduced photorespiration and enhanced photosynthesis that correlated with an increased chloroplastic
CO2 concentration in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase. These effects are evident after
overexpression of the three subunits of glycolate dehydrogenase, but enhanced by introducing the complete bacterial
glycolate catabolic pathway. Diverting chloroplastic glycolate from photorespiration may improve the productivity of
crops with C3 photosynthesis
carbon and nitrogen that occurs in C3 plants when phosphoglycolate, an inevitable by-product of photosynthesis, is recycled
by photorespiration. Using step-wise nuclear transformation with five chloroplast-targeted bacterial genes encoding glycolate
dehydrogenase, glyoxylate carboligase and tartronic semialdehyde reductase, we generated plants in which chloroplastic
glycolate is converted directly to glycerate. This reduces, but does not eliminate, flux of photorespiratory metabolites through
peroxisomes and mitochondria. Transgenic plants grew faster, produced more shoot and root biomass, and contained more
soluble sugars, reflecting reduced photorespiration and enhanced photosynthesis that correlated with an increased chloroplastic
CO2 concentration in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase. These effects are evident after
overexpression of the three subunits of glycolate dehydrogenase, but enhanced by introducing the complete bacterial
glycolate catabolic pathway. Diverting chloroplastic glycolate from photorespiration may improve the productivity of
crops with C3 photosynthesis
The oxidation of glycolate to glyoxylate is an important reaction step in photorespiration. Land plants and charophycean green algae oxidize glycolate in the peroxisome using oxygen as a co-factor, whereas chlorophycean green algae use a... more
The oxidation of glycolate to glyoxylate is an important
reaction step in photorespiration. Land plants and
charophycean green algae oxidize glycolate in the
peroxisome using oxygen as a co-factor, whereas
chlorophycean green algae use a mitochondrial glycolate
dehydrogenase (GDH) with organic co-factors. Previous
analyses revealed the existence of a GDH in the
mitochondria of Arabidopsis thaliana (AtGDH). In this
study, the contribution of AtGDH to photorespiration was
characterized. Both RNA abundance and mitochondrial
GDH activity were up-regulated under photorespiratory
growth conditions. Labelling experiments indicated that
glycolate oxidation in mitochondrial extracts is coupled
to CO2 release. This effect could be enhanced by adding
co-factors for aminotransferases, but is inhibited by the
addition of glycine. T-DNA insertion lines for AtGDH
show a drastic reduction in mitochondrial GDH activity
and CO2 release from glycolate. Furthermore, photorespiration
is reduced in these mutant lines compared with
the wild type, as revealed by determination of the postillumination
CO2 burst and the glycine/serine ratio under
photorespiratory growth conditions. The data show that
mitochondrial glycolate oxidation contributes to photorespiration
in higher plants. This indicates the conservation
of chlorophycean photorespiration in streptophytes
despite the evolution of leaf-type peroxisomes
reaction step in photorespiration. Land plants and
charophycean green algae oxidize glycolate in the
peroxisome using oxygen as a co-factor, whereas
chlorophycean green algae use a mitochondrial glycolate
dehydrogenase (GDH) with organic co-factors. Previous
analyses revealed the existence of a GDH in the
mitochondria of Arabidopsis thaliana (AtGDH). In this
study, the contribution of AtGDH to photorespiration was
characterized. Both RNA abundance and mitochondrial
GDH activity were up-regulated under photorespiratory
growth conditions. Labelling experiments indicated that
glycolate oxidation in mitochondrial extracts is coupled
to CO2 release. This effect could be enhanced by adding
co-factors for aminotransferases, but is inhibited by the
addition of glycine. T-DNA insertion lines for AtGDH
show a drastic reduction in mitochondrial GDH activity
and CO2 release from glycolate. Furthermore, photorespiration
is reduced in these mutant lines compared with
the wild type, as revealed by determination of the postillumination
CO2 burst and the glycine/serine ratio under
photorespiratory growth conditions. The data show that
mitochondrial glycolate oxidation contributes to photorespiration
in higher plants. This indicates the conservation
of chlorophycean photorespiration in streptophytes
despite the evolution of leaf-type peroxisomes
International patent
Cadmium (Cd) is an important industrial agent and environmental pollutant that is a major cause of plants disease. This study was conducted to investigate the impact of Cd on the physiological and molecular traits of garlic growth and... more
Cadmium (Cd) is an important industrial agent and environmental pollutant that is a major cause of plants disease. This study was conducted to investigate the impact of Cd on the physiological and molecular traits of garlic growth and active constituent. The garlic cloves were irrigated with different concentrations of Cd. The obtained results show that the measured pigments and total soluble sugars decreased with increased Cd concentration in growth medium. Meanwhile protein and proline content increases due the important role of proline as osmoregulation of plants, stabilization the protein synthesis machinery and an effective singlet oxygen quencher. Cd supports the activity of antioxidant enzymes (catalase, peroxidase, polyphenol oxidase and superoxide dismutase) as a defense system ROS detoxification during normal metabolism and particularly during stress. Alliinase gene expression in the green leaves of garlic plants was negative correlated with Cd stress. The maximum expression were observed at low concentration of Cd (5 and 10 mM). Higher doses of Cd cause a great reduction in allicin production in garlic leaves.
The cloves of garlic (Allium sativum L.) were exposed to variable doses of gamma rays ranging from 10 to 150 Gy in order to assess their effects on plant growth, morphological variation, biochemical, and molecular traits. There was a... more
The cloves of garlic (Allium sativum L.) were exposed to variable doses of gamma rays ranging from 10 to 150 Gy in order to assess their effects on plant growth, morphological variation, biochemical, and molecular traits. There was a clear correlation between gamma radiation doses and plant growth. Pigments fractions and total carbohydrate contents were also decreased with increasing γ-radiation doses. The level of Proline contents and the activity of antioxidant enzymes; CAT, POD, PPO, and SOD showed gradual increase with increasing the level of γ-radiation up to 100 Gy and thereafter decline. It is interesting to note that abundance of Alliinase gene transcripts which was gradually reduced with the increase of γ-radiation doses.
This study was conducted to investigate the effect of NaCl on ……the physiological and biochemical traits of Chlorella vulgaris. The Alga was exposed to different concentrations of NaCl ranging from 50-300 mM besides control over a period... more
This study was conducted to investigate the effect of NaCl on
……the physiological and biochemical traits of Chlorella vulgaris.
The Alga was exposed to different concentrations of NaCl ranging
from 50-300 mM besides control over a period of 10-20 days. Total
chlorophyll contents and carotenoids levels were increased at low
NaCl concentrations but significantly reduced at higher concentrations. It
is interesting to note that total free amino acids and proline contents
increased at low and moderate NaCl concentrations. The activity of
the antioxidant enzymes; CAT, POD, PPO, and SOD; were noticeably
increased by increasing salt concentration up to 200 mM and
thereafter declined. The photosynthetic related genes expression;
rbcL, psaB, and psbC; were significantly reduced at all NaCl
concentrations. The results indicated that salt stress inhibits PSII
efficiency and reduces the overall CO2 assimilation rate in Chlorella
vulgaris
……the physiological and biochemical traits of Chlorella vulgaris.
The Alga was exposed to different concentrations of NaCl ranging
from 50-300 mM besides control over a period of 10-20 days. Total
chlorophyll contents and carotenoids levels were increased at low
NaCl concentrations but significantly reduced at higher concentrations. It
is interesting to note that total free amino acids and proline contents
increased at low and moderate NaCl concentrations. The activity of
the antioxidant enzymes; CAT, POD, PPO, and SOD; were noticeably
increased by increasing salt concentration up to 200 mM and
thereafter declined. The photosynthetic related genes expression;
rbcL, psaB, and psbC; were significantly reduced at all NaCl
concentrations. The results indicated that salt stress inhibits PSII
efficiency and reduces the overall CO2 assimilation rate in Chlorella
vulgaris
A significant increase in carotenoids, intracellular proline contents, and activity of antioxidative enzymes; catalase, peroxidise, polyphenol oxidase, and superoxide dismutase, was observed in the green microalga Chlorella vulgaris... more
A significant increase in carotenoids, intracellular proline contents, and activity of antioxidative enzymes; catalase, peroxidise, polyphenol oxidase, and superoxide dismutase, was observed in the green microalga Chlorella vulgaris following copper exposure. In contrast, a reduction in Chl a, Chl b, free amino acids and total protein contents was also observed. Real-time PCR shows that Cu treatment reduced significantly the transcript abundance of psbC and rbcL at moderate and high Cu concentrations, whereas the transcript abundance of psaB synergistically increased at lower Cu concentrations and thereafter decline with increasing Cu doses. These results demonstrate that Cu inhibits PSII activity and CO 2 assimilation, but increase the activity of the antioxidative enzymes. Consequently, Chlorella vulgaris showed diverse response to Cu stress on physiological, biochemical and molecular levels.
Six species of L-methioninase producing Aspergillus species, isolated from Egyptian soil, were selected for comprehensive morphotypic and molecular characterization. Based on morphological and physiological features, these isolates were... more
Six species of L-methioninase producing Aspergillus species, isolated from Egyptian soil, were selected for comprehensive morphotypic and molecular characterization. Based on morphological and physiological features, these isolates were identified as Aspergillus flavipes, Aspergillus carneus, Aspergillus flavus, Aspergillus tamari, Aspergillus oryzae, and Aspergillus parasiticus. Regarding to the maximum enzyme productivity by A. flavipes, it was selected as authentic strain for ribosomal ribonucleic acid (rRNA) primer design. Using primer combinations for 18S rRNA and internal transcribed spacers (ITS)1 amplification, these isolates gave the same polymerase chain reaction (PCR) amplicon size, revealing the relative molecular identity. Moreover, using ITS2 primers, among the six isolates, Aspergillus flavipes EK and A. carneus displayed PCR products on agarose gel, approving the actual morphological and biochemical similarities of these two isolates, A. flavipes group. By sequencing of ITS1-5.8S-ITS2 region, blasting and alignment from the data base, A. flavipes EK showed a typical identity to gene bank deposited A. flavipes isolates. The rRNA sequence of A. flavipes EK was deposited to genbank under accession number JF831014.