# data[].attributes.body
Air pollution, heavy metals, soil salinity, drought, high light intensity and high temperature, biotic stress.

# data[].attributes.body
Oxidative stress is defined as an imbalance between production of free radicals and reactive metabolites, so-called oxidants or reactive oxygen species (ROS), and their elimination by protective mechanisms, referred to as antioxidants.

# data[].attributes.body
-Superoxide (-O2-)
-Hydrogen peroxide (H2O2)
-Hydroxyl radical (-OH)
-Singlet oxygen (O2)

# data[].attributes.headline
Main sites of ROS production in plant cells

# data[].attributes.subject
Main sites of ROS production in plant cells

# data[].attributes.body
Mitochondria
Chloroplasts
Membranes

# data[].attributes.body
-Reaction with macromolecules
-Damage to cellular membrane; hydroxyl radicals triggering chain reaction of lipids peroxidation.
-Oxidative damage to proteins. Involve specific amino acid modifications, fragmentation of peptide change, aggregation of crosslinked reaction products and increase to proteolysis.
-DNA base degradation, single stranded breakage, and crosslinking to protein.
-The end result is deletions, mutations, and other damaging effects.

# data[].attributes.body
-GO, glycolate oxidase
-3PGA,3-phosphoglycerate
-RuBisCo, ribulose
1,5-bisphosphate carboxylase/oxygenase
-RuBP, ribulose
1,5-bisphosphate
-SOD,superoxide dismutase
-XO, xanthine oxidase
-CAT, catalase
-APX,ascorbate peroxidase.

# data[].attributes.body
Oxidative stress is a complex chemical and physiological phenomenon encompasses both biotic and abiotic stresses in higher plants and develops as a result of overproduction and accumulation of reactive oxygen species (ROS).

# data[].attributes.body
Oxidative stress is the secondary effect of many types of stress consist of pathogen attack to water-deficit stress that arises from production of free radicals and subsequent ensuing cascade of reactions. Induced damage to cells as a result of the formation of ROS.

# data[].attributes.body
Oxidative stress is a complex chemical and physiological phenomenon that accompanies virtually all biotic and abiotic stresses in higher plants and develops as a result of overproduction and accumulation of reactive oxygen species (ROS).Arises from production of free radicals and subsequent ensuingcascade of reactions.

# data[].attributes.body
The generation of ROS is caused by soil salinity, heavy metals, biotic stress, drought, air pollutants, high temperature and high light intensity.

# data[].attributes.body
Air pollutants,soil salinity,heavy metals,biotic stress,air pollutants, drought and high light as well as temperature intensity causes the generation of ROS.

# data[].attributes.body
The generation of ROS is caused by soil salinity, heavy metals, biotic stress, high light intensity and high temperature, drought and air pollutants.

# data[].attributes.body
Superoxide (-O2-)
Hydrogen peroxide (H2O2)
Hydroxyl radical (˙OH)
Singlet Oxygen (O2)

# data[].attributes.body
Superoxide (˙O2-), hydrogen peroxide (H2O2) and hydroxyl radical (OH•)

# data[].attributes.body
Superoxide radical (O•−2 ), singlet oxygen (1O2), hydrogen peroxide (H2O2) and hydroxyl radical (OH•)

# data[].attributes.body
The main sites of ROS production are chloroplast, peroxisome, mitochondria and cytosol.

# data[].attributes.body
Chloroplast
Mitochondria
Peroxisomes
Apoplast
Plasma membrane
Cell walls
Endoplasmic reticulum

# data[].attributes.body
Cellular damage caused by ROS is:
- Reaction with macromolecules
-Damage to cellular membrane hydroxyl radicals triggering chain
reaction of lipid peroxidation
-Oxidative damage to proteins – involve specific amino acid
modifications, fragmentation of peptide chain, aggregation of
crosslinked reaction products and increased to proteolysis
-DNA – base degradation, single-stranded breakage, and crosslinking
to protein
-Results in deletions, mutations, other damaging genetic effects

# data[].attributes.body
The main sites of ROS production are chloroplasts, mitochondria, peroxisome, apoplast, plasma membrane, cell walls and endoplasmic reticulum (ER).

# data[].attributes.body
Oxidative stress is a complex chemical and physiological phenomenon that accompanies both biotic and abiotic stresses in higher plants and develops as result of overproduction and accumulation of reactive oxygen species (ROS).

# data[].attributes.body
The cellular damage involved reaction with macromolecules. For the damage to cellular membrane, hydroxyl radicals trigger chain reaction of lipid peroxidation. Besides, oxidative damage to proteins involve specific amino acid modifications, fragmentation of peptide chain, aggregation of crosslinked reaction products and increased to proteolysis. The oxidative damage to DNA included base degradation, single-stranded breakage and crosslinking to protein, causing deletions, mutations and other damaging genetic effects.

# data[].attributes.body
The generation of ROS is caused by air pollutants, soil salinity, heavy metals. biotic stress, drought, high light intensity and high temperature.

# data[].attributes.body
The cellular damage caused by ROS involves the reaction with macromolecules. The damage to cellular membrane due to hydroxyl radicals triggering chain reaction of lipid peroxidation. Oxidative damage to proteins involve specific amino acid modifications, fragmentation of peptide chain, aggregation of
crosslinked reaction products and increased to proteolysis. DNA–base degradation, single-stranded breakage, and crosslinking to protein results in deletions, mutations, other damaging genetic effects.

# data[].attributes.body
Superoxide Dismutase (SOD)
Ascorbate peroxidase (APX)
Catalase (CAT)
Monoadehydroascorbate reductase (MDHAR)
Dehydroascorbate reductase (DHAR)
Glutathione reductase (GR)
Guaiacol peroxidase (GPX)

# data[].attributes.body
Superoxide radical (O.-2), singlet oxygen (1O2), hydrogen peroxide (H2O2) and hydroxyl radical (OH.)

# data[].attributes.body
- Chloroplast
- Miitochondria
- peroxisome
- apoplast
- plasma membrane
- endoplasmic reticulum

# data[].attributes.body
Ascorbic acid (AA)
Reduced Glutathione (GSH)
Alpha Tocopherol
Carotenoids
Flavonoids
Proline

# data[].attributes.body
Superoxide Dismutase(SOD), Catalase(CAT), Ascorbate Peroxidase(APX),
Monodehydroascorbate reductase(MDHAR), Dehydroascorbate
reductase(DHAR), Glutathione Reductase(GR) and Guaiacol
Peroxidase(GPX)

# data[].attributes.body
Superoxide Dismutase(SOD), Catalase(CAT)

Ascorbate Peroxidase(APX)

Monodehydroascorbate reductase (MDHAR)

Dehydroascorbate reductase (DHAR)

Glutathione Reductase (GR)

Guaiacol Peroxidase(GPX)

# data[].attributes.body
Ascorbic acid (AA)

Reduced Glutathione (GSH)

α-tocopherol

carotenoids

phenolics

flavonoids

proline.

# data[].attributes.body
SOD: Under environmental stresses, SOD forms the first line of defense against ROS-induced damages. The SOD catalyzes the removal of O−2 by dismutating it into O2 and H2O2. This removes the possibility of OH formation by the Haber-Weiss reaction.
CAT: CAT is a tetrameric heme-containing enzyme responsible for catalyzing the dismutation of H2O2 into H2O and O2.
APX: APX is an integral component of the Ascorbate-Glutathione (ASC-GSH) cycle. While CAT predominantly scavenges H2O2 in the peroxisomes, APX performs the same function in the cytosol and the chloroplast. The APX reduces H2O2 to H2O and DHA, using Ascorbic acid (AA) as a reducing agent.
GSH: GSH scavenges H2O2, 1O2, OH, and O−2 and protects the different biomolecules by forming adducts (glutathiolated) or by reducing them in presence of ROS or organic free radicals and generating GSSG as a by-product. GSH also plays a vital role in regenerating AA to yield GSSG. The GSSG thus generated is converted back to GSH, either by de novo synthesis or enzymatically by GR. GSH also helps in the formation of phytochelatins via phytochelatin synthase

# data[].attributes.body
Superoxide Dismutase (SOD),
Catalase (CAT),
Ascorbate Peroxidase (APX),
Monodehydroascorbate reductase
(MDHAR),
Glutathione Reductase (GR) and
Guaiacol Peroxidase (GPX)

# data[].attributes.body
Aacorbic Acid (AA), Reduced glutathione (GSH), α-tocopherol, carotenoids, phenolics, flavonoids and amino acid cum osmolyte
proline.

# data[].attributes.body
-Ascorbic acid (AA)
-Reduced Glutathione (GHS)
-Alpha - Tocopherol
-Carotenoids
-Flavonoids
-Proline

# data[].attributes.body
SOD - Under environmental stresses,SOD forms the first line of defense against ROS-induced damages. The SOD catalyzes the removal of O•−2 by dismutating it into O2 and H2O2. This removes the possibility of OH• formation by the Haber-Weiss reaction.

CAT - A tetrameric heme-containing enzyme responsible for catalyzing the dismutation of H2O2 into H2O and O2. CAT is unique amongst antioxidant enzymes in not requiring a reducing equivalent. Stressful conditions demand greater energy generation and expenditure of the cell.
This is fulfilled by increased catabolism which generates H2O2. CAT removes the H2O2 in an energy efficient way.

APX- An integral component of the Ascorbate-Glutathione (ASC-GSH) cycle. APX performs dismutation of H2O2
in the cytosol and the chloroplast. The APX reduces H2O2 to H2O and DHA,using Ascorbicacid(AA) as a reducing agent.

GSH - A low molecular weight thioltripeptide (γ-glutamyl-cysteinyl-glycine) with high reductive potential. A central cysteine residue with nucleophilic character
is the source of its reducing power. GSH scavenges H2O2, 1O2, OH • and O•−2 and protects the different biomolecules by forming adducts (glutathiolated) or by reducing them in presence of ROS or organic free radicals and generating GSSG as a by-product. GSH also helps
in the formation of phytochelatins via phytochelatin synthase, which helps to chelate heavy metal ions and thus scavenges another potential source of ROS formation in plants.

# data[].attributes.body
Ascorbic Acid (AA), Reduced glutathione (GSH), alpha tocopherol , carotenoids, phenolics, flavonoids and aminoacidcumosmolyte proline.

# data[].attributes.body
-SOD: Under environmental
stresses, SOD forms the first line of defense against ROS-induced
damages. The SOD catalyzes the removal of O•−2 by dismutat-
ing it into O2 and H2O2. This removes the possibility of OH• formation by the Haber-Weiss reaction.
-CAT: a tetrameric heme-containing enzyme responsible for catalyzing the dismutation of H2O2 into H2O
and O2. This is necessary since stressful conditions demand greater energy generation and expenditure of the cell. This is fulfilled by increased catabolism which generates H2O2. CAT removes the H2O2 in an energy efficient way.
-APX: APX reduces H2O2 to H2O
and DHA, using Ascorbic acid (AA) as a reducing agent in cytosol and chloroplast.
-GSH: GSH scavenges H2O2, 1O2, OH•, and O•−2 and protects the different biomolecules by forming adducts (glutathiolated) or by reducing them in presence of ROS or organic free radicals and generating GSSG as a by-product. GSH also plays a vital role in regenerating AA to yield GSSG.

# data[].attributes.body
The cellular damage caused by ROS involves the reaction with macromolecules. The damage of cellular membrane due to hydroxyl radicals triggering chain reaction of lipid peroxidation. Oxidative damage to proteins involve specific amino acid modifications, fragmentation of peptide chain, aggregation of crosslinked reaction products and increased to proteolysis. DNA-based degradation, single stranded breakage, and crosslinking to protein results in deletions, mutations, other damaging genetic materials.

# data[].attributes.body
SOD: Under environmental
stresses, SOD forms the first line of defense against ROS-induced damages. The SOD catalyzes the removal of O₂•− by dismutating it into O₂ and H₂O₂. This removes the possibility of OH• formation by the Haber-Weiss reaction.

CAT: A tetrameric heme-containing enzyme responsible for catalyzing the dismutation of H₂O₂ into H₂O and O₂. It is
unique amongst antioxidant enzymes in not requiring a reducing equivalent.

APX: While CAT predominantly scavenges H2O2 in the peroxisomes, APX performs the same function in the cytosol and the chloroplast. The APX reduces H2O2 to H2O
and DHA, using Ascorbic acid (AA) as a reducing agent.

GSH: GSH scavenges H2O2, 1O2, OH, and O−2 and protects the different biomolecules by forming adducts (glutathiolated) or by reducing them in presence of ROS or organic free radicals and generating GSSG as a by-product. GSH also plays a vital role in regenerating AA to yield GSSG. The GSSG thus generated is converted back to GSH, either by de novo synthesis or enzymatically by GR. GSH also helps in the formation of phytochelatins via phytochelatin synthase.

# data[].attributes.body
2 Strategies for engineering tolerance to oxidative stress in plants are:
-Increase level of enzymes that remove ROS
-Increase level of antioxidant compounds that react with ROS

# data[].attributes.body
Strategy 1: Expression of enzymes involved in scavenging ROS:

SODs catalyse the reaction – superoxide radical combines with two hydrogen ions – form oxygen and hydrogen peroxide
Broad family of SOD enzymes requiring different metal ions for activity. Predominating different cellular components e.g. transgenic tobacco – containing each class of enzymes – withstand oxidative stress
Not clear – protective effect is due to the removal of superoxide by the
enzyme, or the hydrogen peroxide product enhances stress tolerance by inducing other stress-related genes
Cu/Zn-SOD, Mn/SOD and Fe-SOD genes together in alfalfa – increase
winter hardiness

Strategy 2: Production of antioxidants enzymes
Actions of enzymatic antioxidants ascorbate peroxidase – catalyzed the ascorbate to scavenge ROS glutathione peroxidase – using glutathione (GSH) to reduce H2O2,
producing GSSG glutathione reductase – reduce GSSG to glutathione (GSH), provide resistance to oxidative stress resulting from paraquat treatment.
Glutathione synthase – increasing cellular concentration of gluthatione.

# data[].attributes.body
Increase level of enzymes that remove ROS

Increase level of antioxidant compounds that react with ROS

# data[].attributes.headline
Two strategies for engineering tolerance

# data[].attributes.subject
Two strategies for engineering tolerance

# data[].attributes.body
1) Increase level of enzymes that remove ROS
2) Increase level of antioxidant compounds that react with ROS

# data[].attributes.body
Strategy 1: Expression of enzymes involved in scavenging ROS

SODs catalyse the reaction in which the superoxide radical combines with two hydrogen ions to form oxygen and hydrogen peroxide. Broad family of SOD enzymes
require different metal ions for activity and predominate different cellular components. For an example, transgenic tobacco containing each class of enzymes is able withstand
oxidative stress.

Strategy 2: Production of antioxidants enzymes

Ascorbate peroxidase catalyzed the ascorbate to scavenge ROS. Glutathione peroxidase using glutathione (GSH) to reduce H2O2,
producing GSSG. Glutathione reductase reduce GSSG to glutathione (GSH), provide
resistance to oxidative stress resulting from paraquat treatment. Glutathione synthase increasing cellular concentration of
gluthatione.

# data[].attributes.body
Expression of enzymes involved in scavenging ROS

Production of antioxidants enzymes

# data[].attributes.body
SODs catalyse the reaction of superoxide radical combines with two hydrogen ions to form oxygen and hydrogen peroxide. Broad family of SOD enzymes is requiring different metal ions for activity and predominating different cellular components. For instance, transgenic tobacco containing each class of enzymes is capable to withstand oxidative stress. Cu/Zn-SOD, Mn/SOD and Fe-SOD genes together in alfalfa shown an increase in winter hardiness.

Production of antioxidants enzymes such as ascorbate peroxidase catalyzed the ascorbate to scavenge ROS. Besides, glutathione peroxidase using glutathione (GSH) to reduce H2O2, producing GSSG. Moreover, glutathione reductase reduce GSSG to glutathione (GSH), provide resistance to oxidative stress resulting from paraquat treatment. In addition, glutathione synthase increase cellular concentration of gluthatione.

# data[].attributes.body
Increase expression of enzyme involved in scavenging ROS.

Increase production of antioxidants enzymes

# data[].attributes.body
1. Expression of enzyme involved in scavenging ROS.
-SODs catalyse the reaction
-Superoxide radical combines with two hydrogen ions
-Form oxygen and hydrogen peroxide.

2. Production of antioxidant enzymes
ascorbate peroxidase – catalyzed the ascorbate to scavenge ROS

glutathione peroxidase – using glutathione (GSH) to reduce H2O2,
producing GSSG

glutathione reductase – reduce GSSG to glutathione (GSH), provide
resistance to oxidative stress resulting from paraquat treatment.

Glutathione synthase – increasing cellular concentration of
gluthatione.

# data[].attributes.body
- SOD: Under environmental stresses, SOD forms the first line of defense against ROS- induced damages. The SOD catalyzes the removal of O2- by dismutating it onto O2 and H2O2. This remove the possibility of OH- formation by the Haber-Weiss reaction.
- CAT- A tetrametric heme-containing enzyme responsible for catalyzing the dismutation for H2O2 into H2O and O2. It is unique among antioxidants enzymes in not requiring a reducing equivalent.
- APX- While CAT predominatly scavenges H2O2 in the peroxisomes, APX performs the same function in the cytosol and the chloroplast. The APX reduces  H2O2 to H2O and DHA, using Ascorbic acid as a reducing agent.
- GSH- GSH scavenges H2O2, 1O2, OH and O-2 and protects the different molecules by forming adducts or by reducing them in presence of ROS or organic free radicals and generating GSSG as a by-product.

# data[].attributes.body
In strategy 1, SODS catalyse the reaction of superoxide radial combines with two hydrogen ions to form oxygen and hydrogen peroxide. Broad family of SOD enzymes is requiring different metal ion for activity and presominating different cellular components. For instance, transgenic tobacco containing each class of enzyme is capable to withstand oxidative stress.
In strategy 2, production of antioxidants enzymes such as ascorbate peroxidase catalyzed the ascorbate to scavenge ROS. Besides, glutathione peroxidase using GSH to reduce H2O2 producing GSCC. Moreover, glutathione reductase reduce GSCC to GSH, provide resistance to oxidative stress resulting from paraquat treatment.