Isozyme Profiles Research Articles

Changes in peroxidase and polyphenol oxidase activity and transcript levels of related genes in two egyptian bread wheat cultivars (Triticum aestivum L.) affected by gamma irradiation and salinity stress

The effect of gamma irradiation (100, 200, and 300 Gy) and NaCl (60 and 120 mM) on peroxidase (POD) and polyphenol oxidase (PPO) activities in Sids-1 and Sakha-93 wheat cultivars were investigated. POD and PPO activities increased significantly with increasing NaCl concentrations, and the maximal activity increased at 120 mM NaCl, while PPO activity was higher than POD at the same concentration of NaCl in both the two cultivars. POD and PPO isozymes profile revealed a total of six bands, whereas all of them are variable and exposed the effect of gamma ray and sodium chloride with different genetic response of the two wheat cultivars. The expression level of POD gene in Sakha-93 cultivar was more than in Sids-1. While it was more pronounced at 120 mM NaCl combined with gamma irradiation dose 300 Gy. Gamma ray can be used as a useful tool for gene expression in plants and salt tolerance could be attributed to the constitutive induced antioxidant gene, leading to more efficient enzyme stimulation and protection in wheat.

Enzymatic Analysis of Superoxide Dismutase (SOD) from Hordeum vulgare: Its Role in Drought Stress Tolerance

Superoxide dismutases (SODs) are ubiquitous metalloenzymes that constitute the first line of defense against reactive oxygen species. The role of SOD in neutralizing free radical production has already been documented. In the present investigation we have attempt to study kinetic properties of SODs in three drought sensitive and drought resistant varieties of H. vulgare. The results demonstrated that SOD displayed decreased affinities of substrate binding to their corresponding enzymes under drought conditions. The SOD isozymes profile was also analyzed and it was found that under drought conditions the only two SOD isozymes expressed as against three isozymes expressed under control. These data suggest that the decreased substrate binding affinity to SODs as well as decrease in one isozyme band of SOD under drought condition may be responsible for resistance. These findings may be used to develop drought resistance varieties of other crops.

Plant Defense System Activated in Chili Plants by Using Extracts from Eucalyptus citriodora.

Capsicum annuum L. is infected by Fusarium Wilt and causes significant yield losses in Pakistan. Biological control is an excellent and environment friendly way. Presently, the biocontrol assays were conducted in pot trials using methanolic leaf extract of Eucalyptus citriodora L. where spray of extract prior to infection provided better protection from pathogen with maximum disease control. Further, Native page electrophoresis was performed to find out difference in expression profile of enzyme which revealed that control and T2 (Plant sprayed with Eucalyptus extract) did not exhibit any difference in their isozyme profile signifying no extra load of biological control measure on plant for the production of defense elements until the pathogen arrived. While in case of T3 （Protective treatment） and T4 (Curative treatment) extra isozyme (PO1) was observed in T4 only, PPO1 and PPO5, and PAL 2 and PAL 3 were comprised in higher quantities in T3 and T4 over control exposing the expression of plant metabolism under pathogen attack. The study concludes that the organic extract of E. citriodora have the potential to restrain the disastrous effects of pathogenic fungi. It will lead to the different aspect of biocontrol to suppress the plant pathogenic fungi in a broad spectrum.

Genetic variabilities and relationships among some egyptian Aspergillus spp. based on microscopic characters, isozyme profiles and random amplification of polymorphic DNA

Twelve Aspergillus spp. were isolated from the Egyptian soils and were studied morphologically and microscopically. Isozyme profiles and random amplified polymorphic DNA (RAPD) were also employed for determination of the genetic relationship among the tested Aspergillus spp. Results of RAPD revealed genetic similarity level above 80% between A. terreus and A. aculeatus. The species A. niger, A. candidus, A. terreus and A. aculeatus were joined with a similarity level of 65%. Unique bands were displayed by certain fungi and can be taken as a positive marker for isolate identification. Five isozyme systems; peroxidase, alcohol dehydrogenase, α esterase, β esterase and superoxide dismutase were studied to detect the genetic variabilities among the tested isolates. Subsequently, comparing the three dendrograms which belong to morphological characters, isoymes and RAPD revealed a great relationship between A. terreus and A. niveus from one side and A. candidus and A. terreus from the other side.

<b>Population Profile of Cytochrome P450 Isozymes in the Small Intestine of Japanese </b>

<b>Population Profile of Cytochrome P450 Isozymes in the Small Intestine of Japanese </b>

Effect of Seed Priming on Biochemical Changes in Fresh and Aged Seeds of Cucumber

The present investigation was conducted at the laboratory of Seed Science and Technology, Indian Institute of Horticultural Research, Hessaraghatta, and Bangalore, India during March 2014 to September 2014. The objective of the study was to identify effect of seed priming on biochemical changes in cucumber seeds. This study showed that the enhancement in seed viability and vigor in primed seeds was due to low membrane injury coupled with high enzyme activities (dehydrogenase and amylase). The priming with KH2PO4 and K2HPO4 reduced the electrical conductivity (EC) significantly in seed. With seed priming with KH2PO4 10-3M there was 44 and 45% lower EC values compared to unprimed. This priming with KH2PO4 10-3M and K2HPO410-3M reduced seed leachate values indicating priming initiates the process of repair by stabilizing membrane integrity. priming significantly increased dehydrogenase enzyme in low vigor seeds was noticed. These changes are to the tune of 16 and 21 per cent due to priming with K2HPO410-3M and KH2PO410-3M, respectively in cucumber. Similarly, higher amylase activity was noticed upon priming in low vigor seeds These are to the extent of 2.1, 1.94 folds higher due to priming with K2HPO410-3M and KH2PO410-3M, respectively, in cucumber and 1.4 & 1.4 folds higher due to priming with K2HPO410-3M .Alteration in protein profiles in low vigor seeds compared to high vigor seeds was noticed in the crops. The disappearance of some low molecular weight proteins in low vigor seeds might be the reason for lesser performance of these seeds. Seed priming although not restored all the lost proteins, but induced synthesis of some other proteins which probably might helped in restoration of germination ability and vigor. Esterase Isozyme profiles also showed variation in their number and intensity in less vigor seeds. Primed seeds further exhibited tolerance to abiotic stress condition (high temperature and water stress) as evident from higher germination compared to unprimed. Besides these studies, some advanced studies were initiated in the present investigation to identify changes in proteome profiles and isocitratelyase gene expression in high vigor and low vigor seeds during germination.

Change in activity of detoxifying enzymes in directionally selected population of tea mosquito bug (Helopeltis theivora) (Heteroptera: Miridae) by an organophosphate insecticide

The heteropteran bug, Helopeltis theivora is a polyphagous pest attacking the foliage crop tea and several other crops grown in the old world tropics. Application of synthetic insecticides, especially organophosphate was so far an effective and economic means of conventional management of the pest. Severe selection (bottlenecking) of H. theivora population by exposure to LC80 dose of an organophosphate insecticide, monocrotophos resulted in 105 fold increase in tolerance level in the third generation. The total activity of general esterases (GE) and cytochrome P450 mono-oxygenases (CYP450) analogously increased in insecticide-selected F2 generation by 16.4 and 9.5 fold, respectively. Such enhanced enzyme activity could be related to the higher tolerance levels of the selected bug. Electropherogram of GE and CYP450 of the insecticide-selected generations indicated a change in isozyme profile with their elevated expressions. Induced isozymes in insecticide selected generations were only partially inhibited, when blocked by the insecticide. These findings imply that different groups (zones) of isozymes of the detoxifying enzymes are involved in imparting higher tolerance in insecticide-selected generations. Isozyme profiles of defence enzymes can be used as indices for identifying tolerance level in the field population of H. theivora, enabling tea planters to carry out rapid monitoring of the tolerance status of the pest populations, thereby providing a ready clue to choose an effective insecticide for pest management.

Seed pre-treatment with spermidine alleviates oxidative damages to different extent in the salt (NaCl)-stressed seedlings of three indica rice cultivars with contrasting level of salt tolerance

The effect of seed pre-treatment with the triamine, spermidine (Spd), in mitigating the detrimental effect of NaCl stress in rice is poorly explored. Due to limited available reports, such an investigation was carried out in the seedlings of three indica rice cultivars, IR-64 (salt-sensitive), Nonabokra (salt-tolerant) and Gobindobhog (aromatic and salt-sensitive). The lethal effect of NaCl was particularly noteworthy in the two susceptible cultivars IR-64 and Gobindobhog, as evidenced by extensive tissue-growth inhibition, oxidative damages and chlorophyll degeneration. Seed pre-treatment with Spd could remarkably alleviate stress injury, especially in IR-64 and Gobindobhog, by reverting back from growth retardation and oxidative damages to near-normal conditions. Spd pre-treatment also promoted the levels of osmolytes, particularly proline in Gobindobhog, concomitant with enhanced anthocyanin, cysteine and polyphenol oxidase, but lowered total phenolics and reducing power in the susceptible cultivars. However, the antioxidant enzyme activities were more enhanced in salt-stressed Nonabokra seedlings with Spd, as means of ameliorating cellular NaCl toxicity. A clear-cut variation in GPX, APX, CAT and SOD isozyme profile was discernible among the three cultivars during NaCl stress, with specific isoform(s) being up regulated or down regulated with Spd pre-treatment. Our results indicated that seed treatment with Spd at the pre-sowing stage can promote NaCl tolerance with varying degrees in salt-sensitive and salt-tolerant rice cultivars by alleviating oxidative damages, triggering the antioxidants and osmolytes, and activating the antioxidative enzymes.

Identification and characterization of Memecylon species using isozyme profiling

Background:The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification and systematic studies of medicinal plant species.Objective:In the present study, protein and isozyme profiles for peroxidase, esterase, acid phosphatase, polyphenol oxidase, alcohol dehydrogenase, and alkaline phosphatase of five species of Memecylon (Melastomataceae), Memecylon umbellatum, Memecylon edule, Memecylon talbotianum, Memecylon malabaricum, and Memecylon wightii were investigated.Materials and Methods:Fresh leaves were used to prepare crude enzyme extract for analyzing the five enzymes isozyme variations. Separation of isozymes was carried out using polyacrylamide gel electrophoresis (PAGE) and the banding patterns of protein were scored. Pair-wise comparisons of genotypes, based on the presence or absence of unique and shared polymorphic products, were used to regenerate similarity coefficients. The similarity coefficients were then used to construct dendrograms, using the unweighted pair group method with arithmetic averages.Results:A total of 50 bands with various Rf values and molecular weight were obtained through PAGE analysis. Among the five Memecylon species, more number of bands was produced in M. wightii and less number of bands was observed in M. edule. The results of similarity indices grouped M. malabaricum and M. wightii in one cluster with 98% similarity and M. umbellatum, M. edule, and M. talbotianum are grouped in another cluster with 79% similarity showing close genetic similarities which is in accordance with the morphological identification of Memecylon species.Conclusion:The protein/isozyme fingerprint is useful in differentiating the species and acts as a biochemical marker for identification of Memecylon species.SUMMARY Biochemical characterization of Memecylon species was evaluated by SDS-PAGE of extracted protein and isozyme profiling on native PAGE.After electrophoresis, each gel was stained with specific stains. Genetic distance relationships were evaluated based on the banding patterns of protein on isozymes.Unique banding pattern of esterase, peroxidase, acid phosphatase, alcohol dehydrogenase and polyphenol oxidase are observed in all the five species of Memecylon, which represent the fingerprint of Memecylon species.SDS-PAGE and isozyme profiling of five Memecylon species revealed that M. malabaricum and M. wightii grouped in one cluster and M. umbellatum, M. edule and M. talbotianum grouped in another cluster showing close genetic similarities which is in accordance with the morphological identification of Memecylon species.This is the first report on the comparison of protein and isozyme profile of five different Memecylon species. Abbreviations Used: SDS-PAGE: Sodium docecyl sulfate polyacrylamide gel electrophoresis; NTSYS PC2: Numerical taxonomy system, version 2.2 for Windows XP, Vista, Win7, Win 8 and Win10 including 64 bit

Peroxidase actvity, its isozymes and deterioration of pearl millet [Pennisetum glaucum(L.) R. BR.] flour during storage

Development of off odour and flavour is an old and unresolved problem associated with pearl millet flour during storage and is the major hindrance for their consumer acceptability. In this study role of peroxidase, lipids and phenolics in deterioration of quality of pearl millet in control and stored flour of high (HHB 94) and low (ICMA 94222 x 78/71) rancid genotype was determined. Fat content, fat acidity, free fatty acids, total phenols, C-glycosylflavones content and peroxidase activity of HHB 94 were higher than that of ICMA 94222 x 78/71. Storage of flour for 8 days of these two genotypes showed significant increase in fat acidity and free fatty acids. Storage had no effect on C-glycosylflavones content whereas peroxidase activity reduced significantly with storage time. Isozyme profile showed that pearl millet grains had 3 isozymes of peroxidase and banding pattern was similar in both HHB 94 and ICMA 94222 x 78/71. While banding intensity represented that ICMA 94222 x 78/711 had lesser peroxidase activity as compared to HHB 94. The result suggested that peroxidase activity, fat acidity and free fatty acid value were usually correlated.

Meloidogyne ethiopica and Meloidogyne arenaria parasitizing Oxalis corniculata in Brazil

Meloidogyne ethiopica and Meloidogyne arenaria were identified morphologically and via isozyme profiles of female nematodes extracted from Oxalis corniculata root samples collected from plantations in the municipality of Caicara, Rio Grande do Sul State, Brazil. To the best of our knowledge, this is the first report of M. ethiopica and M. arenaria parasitizing O. corniculata in Brazil.

Molecular identification of an old clinical isolate of Indian Kala-azar.

Molecular characterization is an important task for species identification of the isolates belonging to different Leishmania species. Clinical symptoms, tissue tropism, vector preference, reservoir and geographical distribution may act as distinguishing parameters but not always decisive. On the other hand, modern taxonomic tools employed to divulge characteristics of the genome or protein molecules of the parasite would be convincing and for Leishmania sp., they include nuclear and kDNA buoyant density, multi locus enzyme electrophoresis (MLEE), RAPD, RFLP or use of monoclonal antibodies etc. In the present study, we intend to establish the identification of an old clinical isolate of Indian Kala-azar, familiarly known as 'UR6' by MLEE, RAPD, RFLP and species specific monoclonal antibodies. UR6 has been isolated from a confirmed Kala-azar patient admitted in Calcutta School of Tropical Medicine, Kolkata in 1978. From then it is being regularly used for various scientific studies by the Leishmania Research Group of India and abroad. The isozyme profile of UR6 showed similar electrophoretic mobility that of WHO reference strain for Leishmania tropica, K27. Similar findings were obtained in the RAPD and RFLP assays. Screening with species specific monoclonal antibodies showed its strong reactivity towards L. tropica. The Jaccard's Similarity Indices were calculated.

Effects of Putrescine on Anti-Oxidative Enzymes in Two Rice Cultivars Subjected To Salinity

A study was conducted for elucidation of expression of isozymic profiles with respect to salinity along with putrescine application in two rice varieties cv. Nonabokra and cv. Swarna at 200mM NaCl alone and with 2mM putrescine. Preliminarily these two varieties displays differential pattern of accumulation of Na+ as revealed from SEM micrograph studies. There recorded significant variation in activities in-vitro as well as by in-gel studies of Guaiacol Peroxidase (GPX), Ascorbate Peroxidase (APX), Superoxide Dismutase (SOD), Catalase (CAT) and Glutathione Reductase (GR) enzymes. Activities for GPX, APX and SOD followed significant up regulation under salinity. In contrary CAT and GR enzymes were subdued in both varieties. Putrescine improved the activity for SOD, GPX and APX. CAT and GR maintained stable activity with putrescine. A number of isozymic bands were found with the induction of salinity and putrescine treatment. For SOD three distinct bands were recorded as Cu/Zn/Mn-Fe SOD. For GPX and APX multiple bands were revealed in activity gel. On the contrary CAT was insensitive with the putrescine induction and hardly there recorded any variation. GR isozyme was more prominent in band intensities both in salinity and putrescine. Conclusively different isozymic profiles have contributed to resist salinity along with putrescine.

Variability in Superoxide Dismutase Isoforms in Tall and Dwarf Cultivars of Coconut (Cocos nucifera L.) Leaves

Superoxide dismutases (SODs) are ubiquitous metallo-enzymes that constitute the first line of defense against reactive oxygen species (ROS). They constitute one of the major enzymatic components of detoxi?cation of superoxide radicals generated in biological system by catalyzing its dismutation to H2O2 and finally to H2O and O2. Most plant species contain numerous SOD isoforms differing in their active site metal ions. In the present investigation, we have attempted to identify variability in superoxide dismutase (EC 1.15.1.1) isoform pattern of 13 coconut genotypes comprising six talls, five dwarfs along with two reciprocal hybrids of WCT (Tall) with COD (Dwarf). Among the genotypes studied, a significant variation was observed in SOD enzyme activity as well as in SOD isoforms pattern. A total of eight to fourteen SOD isoforms were detected in different coconut cultivars. The variation was observed only in Mn-SOD isoforms while Fe-SOD (two) and Cu/Zn-SOD (five) isoforms were similar in all the analyzed cultivars. Mn-SOD isoforms varied from one to five in numbers. Among the tall cultivars, WCT, FMST and WCT X COD showed highest number (five) of Mn-SOD isoforms as well as highest enzymatic activity followed by LCT while TPT, PHOT and ADOT showed only single isoform for Mn-SOD. All dwarfs studied were found to have similar SOD isozyme profile for all SODs i.e. one Mn-SOD, five Cu/Zn-SOD and two Fe-SOD isoforms. It was also observed that Mn-SOD does not follow the Mendelian pattern of inheritance i.e. reciprocal crosses showed Mn-SOD isoform pattern similar to their mother palm. SOD activity and isoform pattern can be utilized as a biochemical marker for varietal identification and for abiotic stress/drought tolerance breeding.

Pre-treatment of seeds with salicylic acid attenuates cadmium chloride-induced oxidative damages in the seedlings of mungbean (Vigna radiata L. Wilczek)

Salicylic acid (SA) is known to be responsive to major abiotic stress factors like drought, cold, heavy metal toxicity, and such other forms of osmotic stress. However, molecular regulation of SA signaling, including the mechanism of action in heavy metal stress tolerance, is not well understood, so that currently there is an increasing trend in studies in this area. The present study was focused to assess the possible regulatory role of SA in mitigating oxidative damages under cadmium (Cd) toxicity, taking mungbean (Vigna radiata) seedlings as the experimental model. Pre-soaking of seeds in SA, prior to Cd exposure of germinated seedlings, alleviated the overall detrimental effects of Cd toxicity. The SA-promoted seedling growth under stress was correlated with improved germination percentage due to enhanced α-amylase activity, thereby stimulating tissue growth, biomass, and relative water content. The seedlings showed considerably less chlorophyll degradation or reduced chlorophyllase activity, lesser malondialdehyde and total peroxide content, and increased reducing power. The loss in free amino acid and cysteine pool, and protease activity with Cd stress was overcome by SA-pre-treatment. The restoration to almost the normal level of osmolytes like total sugar and Pro, antioxidants like ascorbic acid, total phenolics and polyphenol oxidase activity, and antioxidative enzymes like catechol peroxidase, ascorbate peroxidase, catalase and superoxide dismutase, in seedlings grown from SA-pre-treated seeds also pointed towards partial Cd stress recovery. Isozyme profiling revealed induction of isoform(s) of guaiacol peroxidase and superoxide dismutase, in particular, in stressed seedlings, grown from SA-pre-treated seeds. Pre-treatment could also overcome the Cd-induced loss in nitrate reductase activity, leading to better nitrogen assimilation. While the decline in pyruvate dehydrogenase and malate dehydrogenase with Cd stress was recovered by SA, the increased succinate dehydrogenase activity with stress was lowered by SA, since lesser malic acid was required for osmotolerance in presence of SA. On the basis of the above observations, it can be concluded that priming with SA before seed sowing can attenuate Cd-induced oxidative stress in mungbean seedlings through induced antioxidative defense mechanism and improving the overall growth performances.

Morphological and physiological changes in esterase and lipid peroxidation of two bean cultivars pre-soaked with potassium nitrate under salt stress.

Two broad bean cultivars (Vicia faba CV Nobaria3 and Vicia faba CV Sakha3) were obtained from Mallwi Agriculture Research Center, El Minia Governorate, Egypt. The seeds were divided into two groups, the first group soaked with distilled water, while the second group were soaked with 3 mM KNO₃, respectively, for 4 hours. Seeds were sown and left to grow for 3 weeks then treated with different concentrations of NaCl (0.0, 40, 80, 120 and 160 mM) by top irrigation, then they left to grow further for 65 days from sowing. Plant samples were collected for some measurements: leaf area, plant height, root length, fresh and dry weight, photosynthetic pigments, carotenoids, soluble sugars, soluble proteins, total free amino acids, esterase enzyme, as well as MDA (malondialdehyde) content. Salinity reduced both fresh and dry weight in two broad bean cultivars, this reduction were more pronounced in Sakha3 than Nobaria3. Seed pre-soaking with KNO₃resulted in enhancement of fresh and dry weight production in both cultivars especially at 40 mM NaCl. Photosynthetic pigments were substantially affected by salt treatment while the carotenoids were increased, seed pre-soaking with KNO₃improved these components. The soluble sugars, amino acids as well as soluble proteins showed various responses with increasing salinity in the cultivars, seed pre-soaking with KNO₃has improved these parameters to some extent. The shoots of two cultivars exhibited significant accumulation of MDA, compared to roots exposed to the highest salinity levels. Pre-soaking seeds with KNO₃did not improve MDA in shoots but enhanced it in roots, however, in most cases still lower than the absolute control. The assessment of the esterase isozyme profiles on 7.5% native polyacrylamide gel revealed the presence of 13 isoforms in two faba bean plants in response to KNO₃pre-soaking and treatments with different concentrations of NaCl.

Exercise-induced changes in tumour LDH-B and MCT1 expression are modulated by oestrogen-related receptor alpha in breast cancer-bearing BALB/c mice.

Monocarboxylate transporters (MCTs) and lactate dehydrogenase A (LDH-A) play important roles in sustaining the glycolytic phenotype seen in cancer. Endurance training improves aerobic capacity; however, whether endurance training alters the metabolic phenotype of a solid tumour, from the perspective of lactate metabolism, is yet to be proven. This study showed that endurance training decreases expression of the MCT1 basigin (CD147) and LDH-A , and also increases LDH-B expression in solid tumours and attenuates tumour lactate metabolism. Similar results for MCT1 and LDH-B were found with inhibition of the oestrogen-related receptor alpha (ERRα). The training effects were not additive to the ERRα effects on MCT1 and LDH-B expression in the tumour, which indicated that exercise-induced alterations in MCT1 and LDH-B expression were modulated by ERRα. These results suggest that endurance training could be a useful tool in cancer therapy, especially in basal-like and luminal-like breast carcinomas. Several factors, including overexpression of lactate dehydrogenase (LDH) and monocarboxylate transporters (MCTs), promote an aerobic lactate production that allows some cancer cells to sustain higher proliferation rates in hostile environments outside the cell. To elucidate the effect of endurance training on the metabolic phenotype of solid tumours, we focused on the tumour expression of LDH-A, LDH-B, MCT1, MCT4, oestrogen-related receptor alpha (ERRα) and LDH isozymes in control (C), trained (T), control+XCT790 (CX) and trained+XCT790 (TX) mice. First, we found that the metabolically altered tumours from the trained animals exhibited lower values for lactate concentration than the control group. The decreased lactate concentration was associated with a shift in the tumour LDH isozyme profile towards LDH-1. These exercise-induced changes were also associated with decreases in the expression of the tumour MCT1, ERRα and CD147 in the trained animals. Secondly, the inhibition of ERRα by treatment of MC4-L2 human breast cancer cells with XCT790 (inverse agonist ligand of ERRα) before injection into the animals not only increased LDH-B expression in the tumour, but also decreased MCT1 expression in the CX group in comparison to the C group. The effects of ERRα inhibition were not additive to the training effects on the expressions of MCT1 and LDH-B in the solid tumours. In conclusion, our results suggest that exercise-induced suppression of ERRα expression modulates alterations in solid tumour expression of LDH-B and MCT1 and contributes towards the prevention of tumour development.

Alterations in Protein and Isozymes Profiles during Accelerated Ageing in Soybean (Glycine Max(L.) Merrill)

This study was done to observe alterations in protein and isozyme profiles for soybean (Glycine max (L.) Merrill), during accelerated aeging. During the aeging period some physiological (percent germination, seedling vigour index and germination index) and biochemical (electrical conductivity, malonaldehyde content, total soluble sugars, total soluble proteins, peroxidase and dehydrogenase activity) changes were also observed in relation to seed vigour and viability in fresh and aged soybean seeds. Results showed an overall decrease in germination, vigour, soluble sugars and soluble protein content with increase in ageing duration. Increased activity of lipid peroxidation and electrical conductivity coupled with significant reduction in activities of peroxidase and dehydrogenase were noticed in accelerated aged seeds. Alterations in protein and isozymes profiles in aged seeds compared to fresh seeds indicated that the loss in seeds quality might be due to the adverse effect of ageing on proteins. The electrophoretic variations in protein and isozymes noticed in this study could be used as a criterion in assessing the quality of soybean.

Characterization of Peroxidase Changes in Tolerant and Susceptible Soybeans Challenged by Soybean Aphid (Hemiptera: Aphididae).

Changes in protein content, peroxidase activity, and isozyme profiles in response to soybean aphid feeding were documented at V1 (fully developed leaves at unifoliate node, first trifoliate leaf unrolled) and V3 (fully developed leaf at second trifoliate node, third trifoliate leaf unrolled) stages of soybean aphid-tolerant (KS4202) and -susceptible (SD76R) soybeans. Protein content was similar between infested and control V1 and V3 stage plants for both KS4202 and SD76R at 6, 16, and 22 d after aphid introduction. Enzyme kinetics studies documented that control and aphid-infested KS4202 V1 stage and SD76R V1 and V3 stages had similar levels of peroxidase activity at the three time points evaluated. In contrast, KS4202 aphid-infested plants at the V3 stage had significantly higher peroxidase activity levels than control plants at 6 and 22 d after aphid introduction. The differences in peroxidase activity observed between infested and control V3 stage KS4202 plants at these two time points suggest that peroxidases may be playing multiple roles in the tolerant plant. Native gels stained for peroxidase were able to detect differences in the isozyme profiles of aphid-infested and control plants for both KS4202 and SD76R.

Spermine reduces salinity-induced oxidative damage by enhancing antioxidative system and decreasing lipid peroxidation in rice seedlings

Spermine (Spm) counteracted the adverse effects of salt-induced oxidative stress in leaves of rice (Oryza sativa L.) seedlings by reducing lipid peroxidation and increasing activities of antioxidative enzymes. Seedlings (25 days old) of two rice cultivars (salt-sensitive IR-28 and salt-tolerant CSR-10) were exposed to 50 and 100 mM salt stress with or without 0.1 and 1 mM Spm for 10 days. Salt stress significantly enhanced oxidative stress as measured by increase in superoxide (.O2 −) level and H2O2 content, lipid peroxidation [MDA, and lipoxygenase (LOX) activity] in both the rice cultivars; however, the increase was more pronounced in IR-28. The activities of antioxidant enzymes viz. catalase (CAT) and ascorbate peroxidase (APX) decreased under salt stress while the activities of superoxide dismutase (SOD), peroxidase (POX) and glutathione reductase (GR) increased. Spermine treatment could to some extent alleviate the detrimental effects of salinity by reducing oxidative stress, lipid peroxidation, and increasing SOD, CAT, POX, APX and GR activities and 0.1 mM Spm treatment was more effective. Isozyme profile of these antioxidant enzymes revealed reduction in the intensity of variants of SOD (SOD2 and SOD3 in IR-28 and SOD3 in CSR-10) and one of POX (POX2) under saline conditions. The Spm treatment resulted in increase in the intensity of these bands. It is inferred that application of Spm reduces the effect of salt stress through the regulation of stress related components such as oxidative stress and antioxidative system.