Punesh Sangwan

Effect of Chromium(VI) Toxicity on Enzymes of Nitrogen Metabolism in Clusterbean (Cyamopsis tetragonoloba L.)

Heavy metals are the intrinsic component of the environment with both essential and nonessential types. Their excessive levels pose a threat to plant growth and yield. Also, some heavy metals are toxic to plants even at very low concentrations. The present investigation (a pot experiment) was conducted to determine the affects of varying chromium(VI) levels (0.0, 0.5, 1.0, 2.0, and 4.0 mg chromium(VI) kg−1 soil in the form of potassium dichromate) on the key enzymes of nitrogen metabolism in clusterbean. Chromium treatment adversely affect nitrogenase, nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase in various plant organs at different growth stages as specific enzyme activity of these enzymes decreased with an increase in chromium(VI) levels from 0 to 2.0 mg chromium(VI) kg−1 soil and 4.0 mg chromium(VI) kg−1 soil was found to be lethal to clusterbean plants. In general, the enzyme activity increased with advancement of growth to reach maximum at flowering stage and thereafter decreased at grain filling stage.

β-Propeller phytases: Diversity, catalytic attributes, current developments and potential biotechnological applications

Phytases are phosphatases which stepwise remove phosphates from phytic acid or its salts. β-Propeller phytase (BPPhy) belongs to a special class of microbial phytases that is regarded as most diverse, isolated and characterized from different microbes, mainly from Bacillus spp. BPPhy class is unique for its Ca2+-dependent catalytic activity, strict substrate specificity, active at neutral to alkaline pH and high thermostability. Numerous sequence and structure based studies have revealed unique attributes and catalytic properties of this class, as compared to other classes of phytases. Recent studies including cloning and expression and genetic engineering approaches have led to improvements in BPPhy which provide an opportunity for extended utilization of this class of phytases in improving animal nutrition, human health, plant growth promotion, and environmental protection, etc. This review describes the sources and diversity of BPPhy genes, biochemical properties, Ca2+ dependence, current developments in structural elucidation, heterogeneous expression and catalytic improvements, and multifarious applications of BPPhy.

Cloning, Sequencing, and In Silico Analysis of β-Propeller Phytase Bacillus licheniformis Strain PB-13.

β-Propeller phytases (BPPhy) are widely distributed in nature and play a major role in phytate-phosphorus cycling. In the present study, a BPPhy gene from Bacillus licheniformis strain was expressed in E. coli with a phytase activity of 1.15 U/mL and specific activity of 0.92 U/mg proteins. The expressed enzyme represented a full length ORF “PhyPB13” of 381 amino acid residues and differs by 3 residues from the closest similar existing BPPhy sequences. The PhyPB13 sequence was characterized in silico using various bioinformatic tools to better understand structural, functional, and evolutionary aspects of BPPhy class by multiple sequence alignment and homology search, phylogenetic tree construction, variation in biochemical features, and distribution of motifs and superfamilies. In all sequences, conserved sites were observed toward their N-terminus and C-terminus. Cysteine was not present in the sequence. Overall, three major clusters were observed in phylogenetic tree with variation in biophysical characteristics. A total of 10 motifs were reported with motif “1” observed in all 44 protein sequences and might be used for diversity and expression analysis of BPPhy enzymes. This study revealed important sequence features of BPPhy and pave a way for determining catalytic mechanism and selection of phytase with desirable characteristics.

Biodiversity of the Genus Penicillium in Different Habitats

Abstract Penicillium is a genus of ascomycetous fungi and has an important role in various natural processes. The wide and ubiquitous presence of the Penicillium species has been researched in several studies. According to a comprehensive literature analysis Penicillium is one of the most common fungi occurring in various environments such as soil, air, and extreme environments (temperature, salinity, water deficiency, and pH) and is also associated with plants and specific food products. Due to its huge diversity and existence in extreme environments there is great potential in using it for various environmental, biotechnological, and industrial applications. This chapter describes how to isolate and identify Penicillium species and its diversity in various habitats as well as insight in its selectivity.

Management of Environmental Phosphorus Pollution Using Phytases: Current Challenges and Future Prospects

Phosphorus is an important element for plant and animal nutrition considering its diverse roles in their growth and development. It is derived from different organic and inorganic sources rich in phosphorus. Inorganic sources are most commonly used for development of phosphorus fertilisers while organic sources like phytic acid phosphorus of plant origin is a major source of phosphorus in animal nutrition. Excessive application of phosphorus fertilisers without proper analysis of its soil concentration results in high phosphorus and associated heavy metals deposition in agricultural soils. This has multiple environmental consequences like loss of biological diversity in aquatic system due to phosphate runoff from soil by rain water. Further, inability of monogastric animals to hydrolyse phytate phosphorus and utilise it makes it necessary to supplement external phosphorus in animal feed. This leads to increased phosphorus load and release of excess phosphorus in faecal material at intensive livestock production area, which contributes to environmental phosphorus pollution. The supplementation of animal feeds with microbial phytases increases the bioavailability of phosphorus and minerals besides reducing the aquatic phosphorus pollution in the areas of intensive livestock production. Phytases are of significant value in effectively combating environmental phosphorus pollution. This chapter describes different application of phosphorus, its pollution consequences and use of phytases for strategic management of this problem phosphorus pollution and various promises and challenges therein.

Chromium (VI) Induced Biochemical Changes and Gum Content in Cluster Bean (Cyamopsis tetragonoloba L.) at Different Developmental Stages

Chromium (Cr) contamination by various industries and other activities is known to inhibit plants growth and development. The present study was conducted using pot experiments in a net house to determine the effect of Cr (VI) on biochemical parameters such as photosynthetic pigments, reducing sugars, and important minerals at different stages of growth in leaves, stem, and roots of clusterbean, a multipurpose fodder crop including a source of guar gum. Guar gum content was estimated in seeds at maturity. All biochemical contents showed a great variation with respect to increase in Cr concentration at different stages of growth. The levels of K, Fe, and Zn decreased, while Cr and Na content increased with increase in Cr concentration. Cr induced toxicity in clusterbean appears at 0.5 mg Cr (VI) Kg−1 soil with maximum inhibitory effect at 2 mg Cr (VI) Kg−1 soil, where impaired sugar supply resulted in decreased guar gum synthesis and altered micronutrient content. The study reveals the possible role of these biochemical parameters in decreasing plant growth and development under heavy metal stress.

Phytoremediation: A Biotechnological Intervention

Phytoremediation, a growing sector of bioremediation, exploits the natural ability of a large variety of plants to filter chemicals through their root systems and to aerate the soil, allowing different microorganisms to grow. Phytoremediation has many advantages over other existing technologies in terms of safe and nondisturbing natural surroundings of contaminated sites. The modification in technology leads to different methods of phytoremediation, including phytotransformation, rhizoremediation, phytostabilization, phytoextraction and rhizofiltration. The application of a selected method depends on the nature and site of contaminant. To understand the mechanism of hyperaccumulation, various studies have been conducted on model (Arabidopsis thaliana) and commonly grown plants such as Populus, Brassica, Hydrilla etc. in phytoremediation. Further, based on mechanism and identified genes such as those involved in uptake, sequestration, remobilization and homeostasis, transgenic plants were designed and used efficiently to remove heavy metals and organic chemicals from the soil. However, further efforts are required for advancements in efficiency and robustness of transgenic plants and to popularize the phytoremediation technology on a commercial scale.

Ameliorative Approaches for Management of Chromium Phytotoxicity: Current Promises and Future Directions

Chromium is a heavy metal of serious environmental implications in excess amounts as it poses a threat to human health as well as plant growth and development. Considering limited agricultural land for such a large population and increasing heavy metal pollution in soil, there is an immense need of strategies for alleviation of phytotoxic effects of chromium and its removal from soil. Several studies have been carried out in relation to the aforementioned problems with emphasis on application of plant growth regulators (kinetin, gibberellic acid, brassinosteroids, salicylic acid) and metal chelators (EDTA), bioremediation using microbial inoculants, and reduction of the toxic form of chromium to a nontoxic form. These approaches have been shown to be promising in one or more soil and environmental conditions and plant types. In this chapter, these strategies are discussed considering their chromium amelioration potential from supporting evidences and challenges ahead for successful implementation of any strategy as a universal approach.

Ethyl methane sulphonate (EMS) mediated changes in callus growth of clusterbean (Cyamopsis tetragonoloba L.) raised under saline conditions

Soil salinity is the major biotic stress, which restricts the distribution and productivity of the crops. Agricultural production in the future will increasingly rely on our ability to grow plants on salt affected and marginal lands using saline water. Ethyl methane sulphonate is the most commonly used chemical mutagen to increase genetic variability in crop plants and could be useful in increased plant tolerance to salinity. Clusterbean is one of the most important summer annual legume. In the present study, aseptically grown7-day old seedling explants of clusterbean viz. cotyledon, cotyledonary node, hypocotyl and the embryo axis (cut on radical side) were cultured on MS medium + B5 vitamins (MSB5 medium) supplemented with various growth regulators. Among various explant tried, cotyledonary node gave good response in terms of callus growth which was further selected for future experimentation. The best medium for callus growth was MSB5 with 2 mgl-1 2,4-D and 1 mgl-1 BAP. All the calli produced were compact and their color changed with increase of salt concentration from greenish to brownish green, dark brownish and finally blackish at 200 mM NaCl. Further, calli pieces dipped in sterile liquid MS medium adjuncted with aqueous filter sterilized solution of 0.5% EMS for a range of time duration (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 h) were raised on MSB5 medium without NaCl. These calli were subcultured on the above medium with or without 200 mM NaCl. EMS treatment of 2.5, 3.0 and 3.5h duration improved callus growth on salt amended medium; growth being maximum after 3.0h EMS treatment. It seems that exposing mutagen treated calli to salinity/ salt stress, forces these to face stress doubly-ionic toxicity and toxic effects of mutagen. The survival and regeneration of the putative variant calli is suppressed under such circumstances.