Khalid Rehman Hakeem

Role of Glutathione Reductase in Plant Abiotic Stress

Abiotic stresses severely affect the growth, development, and ultimately yield of the plant, which results in heavy economic losses and food crisis. Oxidative stress, which is associated with almost all the abiotic stresses, is due to over production of toxic reactive oxygen species (ROS) including superoxide ion, hydrogen peroxide, and hydroxyl radicals. Plants combat the oxidative stress via enzymatic and non-enzymatic machinery. Glutathione reductase (GR) is one of the potential enzymes of the enzymatic antioxidant system, which sustains the reduced status of GSH via Ascorbate–Glutathione pathway and plays a vital role in maintenance of sulfhydryl (–SH) group and acts as a substrate for glutathione-S-transferases. GR has been characterised and has been used in the transgenics to provide the plants with tolerance against the oxidative stress.

Nitrogen-efficient rice cultivars can reduce nitrate pollution

IntroductionEnvironmental pollution by un-utilized nitrogenous fertilizer at the agricultural field is one of the key issues of the day. Rice-based cropping system, the mainstay of Indian agriculture, is one of the main sources of unused N-fertilizer since rice utilizes only 30–40% of total applied N, and the rest goes to waste and creates environmental as well as economic loss.MethodsIdentification of rice genotypes that can grow and yield well at low nitrogen levels is highly desirable for enhancement of nitrogen use efficiency (NUE). In the present study, we have identified large variability in the NUE of rice cultivars on the basis of plant with low, medium, and high levels of N in nutrient solution. To establish the basis of this wide variability in NUE, nitrate uptake kinetics and enzymes of nitrate assimilation were studied.Results and discussionThe data of nitrate uptake kinetics revealed that the nitrate uptake is mediated by low-affinity transporter system (LATS) in N-inefficient rice cultivars and by both LATS and high-affinity transporter systems (HATS) in N-efficient genotypes. Activities of nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and the soluble protein content were found to be increased in moderately N-efficient and low N-efficient cultivars with increase in external supply of nitrogen. However, a non-significant decrease in these enzymes was recorded in high N-efficient cultivars with the increase in N supply.ConclusionsThis study suggests that the HATS, high NR, and glutamine synthetase activity and the soluble protein content distribution have a key role in N efficiency of rice genotypes. These parameters may be considered in breeding and genetic engineering programs for improving the NUE of rice, which might be helpful in reducing the fertilizer loss, hence decreasing environmental degradation and improving crop productivity through improvement of nitrogen utilization efficiency in rice.

Potassium starvation-induced oxidative stress and antioxidant defense responses in Brassica juncea

In this study, changes in growth, chlorophyll pigments, proline, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and antioxidative enzyme activities were investigated in the seedlings of four different cultivars (cvs) of mustard [Brassica juncea (L.) Czern. & Coss.], i.e. Varuna, RH-30, Rohini, and Vaibhave under potassium (K) nutrition-deficient conditions. K deficiency induced a significant decrease in concentrations of photosynthetic pigments in all four cvs, however, this decrease was higher in cvs. Varuna and RH-30. During K deficiency, proline concentration increased in all mustard cvs, but a maximum increase in this parameter was shown by cvs. Varuna and RH-30. The activity of the key proline metabolizing enzyme γ-glutamyl kinase increased more in cvs. Varuna and RH-30 compared to cvs. Rohini and Vaibhave. The proline oxidase activity showed greater increase in cvs. Vaibhave and Rohini compared to cvs. Varuna and RH-30. K deficiency increased the concentrations of H2O2 and the activities of anti-oxidative defense system enzymes like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in the seedlings of all mustard cvs, but higher activities of these enzymes were observed in cvs. Varuna and RH-30 compared to cvs. Rohini and Vaibhave. A significant lipid peroxidation in terms of MDA contents was also observed in the K-deficient seedlings of all four mustard cvs. This study suggests that K-starvation-induced oxidative stress through the high generation of reactive oxygen species (ROS). All mustard cvs counteracted to some extent the effects of ROS by activation of antioxidant machinery. Overall, the results indicate that of all four mustard cvs, Varuna and RH-30 were tolerant to K deficiency.

Relevance of Proteomic Investigations in Plant Abiotic Stress Physiology

Plant growth and productivity are influenced by various abiotic stresses. Stressful conditions may lead to delays in seed germination, reduced seedling growth, and decreased crop yields. Plants respond to environmental stresses via differential expression of a subset of genes, which results in changes in omic compositions, such as transcriptome, proteome, and metabolome. Since the development of modern biotechnology, various research projects have been carried out to understand the approaches that plants have adopted to overcome environmental stresses. Advancements in omics have made functional genomics easy to understand. Since the fundamentals of classical genomics were unable to clear up confusion related to the functional aspects of the metabolic processes taking place during stress conditions, new fields have been designed and are known as omics. Proteomics, the analysis of genomic complements of proteins, has caused a flurry of activity in the past few years. It defines protein functions in cells and explains how those protein functions respond to changing environmental conditions. The ability of crop plants to cope up with the variety of environmental stresses depends on a number of changes in their proteins, which may be up- and downregulated as a result of altered gene expression. Most of these molecules display an essential function, either in the regulation of the response (e.g., components of the signal transduction pathway), or in the adaptation process (e.g., enzymes involved in stress repair and degradation of damaged cellular contents), allowing plants to recover and survive the stress. Many of these proteins are constitutively expressed under normal conditions, but when under stress, they undergo a modification of their expression levels. This review will explain how proteomics can help in elucidating important plant processes in response to various abiotic stresses.

Polyamines: Role in Plants Under Abiotic Stress

Environmental changes, irrespective of source, cause a variety of stresses in plants. These stresses affect the growth and development and trigger a series of morphological, physiological, biochemical and molecular changes in plants. Abiotic stress is the primary cause of crop loss worldwide. The most challenging job before the plant biologists is the development of stress tolerant plants and maintenance of sufficient yield of crops in this changing environment. Polyamines can be of great use to enhance stress tolerance in such crop plants. Polyamines are small organic polycations present in all organisms and have a leading role in cell cycle, expression of genes, signaling, plant growth and development and tolerance to a variety of abiotic stresses. High accumulation of polyamines (putrescine, spermidine and spermine) in plants during abiotic stress has been well documented and is correlated with increased tolerance to abiotic stress. Genetic engineering of PA biosynthetic genes in crop plants is the way to create tolerance against different stresses. The present review throws light on the role of polyamines in plants.

Cadmium toxicity induced alterations in the root proteome of green gram in contrasting response towards iron supplement

Cadmium signifies a severe threat to crop productivity and green gram is a notably iron sensitive plant which shows considerable variation towards cadmium stress. A gel-based proteomics analysis was performed with the roots of green gram exposed to iron and cadmium combined treatments. The resulting data show that twenty three proteins were down-regulated in iron-deprived roots either in the absence (−Fe/−Cd) or presence (−Fe/+Cd) of cadmium. These down-regulated proteins were however well expressed in roots under iron sufficient conditions, even in the presence of cadmium (+Fe/+Cd). The functional classification of these proteins determined that 21% of the proteins are associated with nutrient metabolism. The other proteins in higher quantities are involved in either transcription or translation regulation, and the rest are involved in biosynthesis metabolism, antioxidant pathways, molecular chaperones and stress response. On the other hand, several protein spots were also absent in roots in response to iron deprivation either in absence (−Fe/−Cd) or presence (−Fe/+Cd) of cadmium but were well expressed in the presence of iron (+Fe/+Cd). Results suggest that green gram plants exposed to cadmium stress are able to change the nutrient metabolic balance in roots, but in the mean time regulate cadmium toxicity through iron supplements.

Mangrove Ecosystems of Asia

Unlike other types of forests which are more spatially widespread and can be found on varied soil types, the mangrove swamp forests are restricted to sheltered coasts, islands, lagoons, estuaries and rivers on muddy substrates. As an ecosystem it is an important habitat for diverse wildlife, including fishes, shells and microbes and a number of specialized plant forms. It is also of great socioeconomic importance as a hydrological regulator, playing an important role in flood mitigation, buffering against saline intrusion and waves. It is also an important source for fuelwood, timber resources and provides a variety of produce used by local inhabitants. Despite these values, mangrove swamp forests are rapidly being cleared, degraded and transformed to other land-uses, especially for agriculture, aquaculture, resettlement, industrial and ecotourism infrastructures. In view of the recognized values, it is urgent that more suitable areas are protected for not only the biodiversity conservation purposes but also as a special and unique forest type. In Malaysia, a working plan for the Matang mangrove forest reserve, Perak (fifth revision) provides a comprehensive overview of the management and conservation of the mangrove ecosystem in Malaysia, which could also be a model for other mangrove areas in other states for their protection and management. In the long term, systematic and holistic planning represent the best means of achieving sustainable mangrove swamp forest management by incorporating conservation principles and forestry objectives.

Phytoremediation: Mechanisms and Adaptations

Metal contamination of soils is ubiquitous around the globe. Metals accumulate in the soils to toxic levels that may lead to accumulation of metals in plants to unacceptable levels. Metal accumulation is a subject of serious concern due to the threat to plant growth, soil quality, animal and human health. Cleaning up of the soils to remove metals is a current necessity, but it is a challenging task. Different technologies being used nowadays are ex situ which ensues in destruction of soil structure thus leaving it non-useable with poor vegetative cover. Growing plants to clean up the soils is a cost-effective and environmentally friendly alternative. Phytoremediation seems attractive due to non-invasive and non-destructive technology which leaves the soil intact and biologically productive. Plants use different adaptive mechanisms to accumulate or exclude metals, thus maintaining their growth. Accumulation and tolerance of metals by the plants is a complex phenomenon. Movement of metals across the root membrane, loading and translocation of metals through the xylem and sequestration and detoxification of metals at cellular and whole plant levels are important mechanisms adopted by accumulator plants. Understanding the mechanism involved in phytoremediation is necessary to effectively use this technique for metal-contaminated soils. This chapter discusses different mechanisms adopted by plants for remediation of metal-contaminated soils.

Contrasting Effects of Farmyard Manure (FYM) and Compost for Remediation of Metal Contaminated Soil

We investigated effect of farm yard manure (FYM) and compost applied to metal contaminated soil at rate of 1% (FYM-1, compost-1), 2% (FYM-2, compost-2), and 3% (FYM-3, compost-3). FYM significantly (P < 0.001) increased dry weights of shoots and roots while compost increased root dry weight compared to control. Amendments significantly increased nickel (Ni) in shoots and roots of maize except compost applied at 1%. FYM-3 and -1 caused maximum Ni in shoots (11.42 mg kg−1) and roots (80.92 mg kg−1), respectively while compost-2 caused maximum Ni (14.08 mg kg−1) and (163.87 mg kg−1) in shoots and roots, respectively. Plants grown in pots amended with FYM-2 and compost-1 contained minimum Cu (30.12 and 30.11 mg kg−1) in shoots, respectively. FYM-2 and compost-2 caused minimum zinc (Zn) (59.08 and 66.0 mg kg−1) in maize shoots, respectively. FYM-2 caused minimum Mn in maize shoots while compost increased Mn in shoots and roots compared to control. FYM and compost increased the ammonium bicarbonate diethylene triamine penta acetic acid (AB-DTPA) extractable Ni and Mn in the soil and decreased Cu and Zn. Lower remediation factors for all metals with compost indicated that compost was effective to stabilize the metals in soil compared to FYM.

Effect of humidity on egg hatchability and reproductive biology of the bamboo borer (Dinoderus minutus Fabricius)

Wood products are highly exposed to infestation by powder post beetles. Dinoderus minutus (bamboo borer) is a wood boring beetle that seriously damage dried bamboo and finished bamboo products. Management of D. minutus using pesticides showed negative effects on environment despite being very costly. By understanding influence of natural climatic conditions on their reproductive behaviour, could help us to develop a cost effective and environmental friendly strategy to cope up with this problem. In the present study, reproductive parameters and egg development of the bamboo borer were determined at 20%, 40%, 56%, 75% and 85% r.h. levels at constant temperature of 30° ± 2°C with 8 L-16D photoregime. From the results, eclosion to first instar larva was recorded at all relative humidities tested. The lowest shortest percentage of hatchability was recorded at 20% and 85% relative humidity with a mean incubation period of 4.63 ± 0.25 and 10.43 ± 0.32 days, respectively. It was noted that pre-ovipositional period decreased from 14.20 ± 0.49 to 7.20 ± 0.31 days as relative humidity increased from 20% to 75% and slightly increased to 8.00 ± 0.37 days at 85% relative humidity. We conclude that female beetles may have a particular hygropreference in oviposition as total egg production increased with increasing relative humidity.