Reiaz Ul Rehman

Tomato Rab11a characterization evidenced a difference between SYP121 dependent and SYP122 dependent exocytosis

The regulatory functions of Rab proteins in membrane trafficking lie in their ability to perform as molecular switches that oscillate between a GTP- and a GDP-bound conformation. The role of tomato LeRab11a in secretion was analyzed in tobacco protoplasts. Green fluorescent protein (GFP)/red fluorescent protein (RFP)-tagged LeRab11a was localized at the trans-Golgi network (TGN) in vivo. Two serines in the GTP-binding site of the protein were mutagenized, giving rise to the three mutants Rab11S22N, Rab11S27N and Rab11S22/27N. The double mutation reduced secretion of a marker protein, secRGUS (secreted rat beta-glucuronidase), by half, whereas each of the single mutations alone had a much smaller effect, showing that both serines have to be mutated to obtain a dominant negative effect on LeRab11a function. The dominant negative mutant was used to determine whether Rab11 is involved in the pathway(s) regulated by the plasma membrane syntaxins SYP121 and SYP122. Co-expression of either of these GFP-tagged syntaxins with the dominant negative Rab11S22/27N mutant led to the appearance of endosomes, but co-expression of GFP-tagged SYP122 also labeled the endoplasmic reticulum and dotted structures. However, co-expression of Rab11S22/27N with SYP121 dominant negative mutants decreased secretion of secRGUS further compared with the expression of Rab11S22/27N alone, whereas co-expression of Rab11S22/27N with SYP122 had no synergistic effect. With the same essay, the difference between SYP121- and SYP122-dependent secretion was then evidenced. The results suggest that Rab11 regulates anterograde transport from the TGN to the plasma membrane and strongly implicate SYP122, rather than SYP121. The differential effect of LeRab11a supports the possibility that SYP121 and SYP122 drive independent secretory events.

Characterization of Actinomycetes and Trichoderma spp. for cellulase production utilizing crude substrates by response surface methodology

Laboratory bench scaling was done and an average of 1.85 fold increase by Response Surface Methodology (RSM) optimization was obtained. It was found that the predicted value (4.96 IU/ml) obtained by RSM is in close accordance with observed activity 5.14 IU/ml. Endoglucanases are mainly induced by CMC while Wheat bran (natural substrate) exoglucanase is more active when induced by avicel and cellulose. Addition of substrate beyond a level caused inhibition of cellulase production. The molecular weight of protein as determined by SDS-PAGE is very similar to molecular weight of cellulase of Trichoderma viride (T. viride) cellulase and Trichoderma reesei (T. reesei) endoglucanase. T. reesei β-glucosidase has high enzymatic activity on CMC substrate when compared with T. viride β-glucosidase. Secondary structure analysed by using Circular Dichroism confirmed that composition of celluase system is very similar to other analysed species. The cellulase was found to be active in pH range of 4.8-5.5; while temperature range varied from 50°C to 70°C. Although the enzymatic activity produced by mutants were lesser than the parent, but in one case mutants of Trichoderma reesei’s BGL has shown higher activity on cellulose.

Plant signaling: Understanding the molecular crosstalk

Among abiotic factors, salinity and drought stress affect every aspect of plant from physiology to metabolic activities. Understanding of abiotic stress responses and signal transduction to control adaptive pathways is a crucial step in determining the plant resistance exposed to unfavorable environments. Molecular and genomic fi ndings have shown several changes in gene expression profi ling under drought and salt stresses in plants. Numbers of transcription factors which are accountable for inducing stress-responsive genes have been documented. To survive in adverse condition, plants have stress‐specifi c and adaptive responses which provide them necessary protection. Although, there are several signaling pathways and stress-responsive perceptions, some of which are defi nite in function, while others may have cross talk. Expressions of a large number of transcripts and genes are induced by these abiotic stresses in plants which facilitate stress tolerance and stress response. Recently, progress has been made in investigating the complex cascades of gene expression in stress responses. Knowledge about plant stress signaling is essential for the development of transgenic and improving breeding strategies in crops under stress environment. This chapter provides an outline of the common features of stress signaling in plants with some current studies on the functional analysis of signaling machineries under salt and drought stresses.

Signaling in Response to Cold Stress

World population is growing at a fast pace and is projected to reach 6.5 billion by 2050. At the same time, numbers of changes that are occurring in regular environmental parameters are posing threats to the agricultural productivity. Thus, feeding 6.5 mouths would indeed be a huge challenge. Besides the ever-growing human population and alterations in environmental scenarios, reduction in the area of land used for agriculture, declination of crop productivity, overexploitation of bioresources, mal-agricultural practices, and deleterious abiotic environmental stresses are leading to ecological imbalance. To reduce these losses scientists all over the world focus on novel strategies to enhance crop production in order to meet the increasing food demand and establish a balance among different ecological factors. The various abiotic stress conditions such as cold, temperature, drought and salinity cause noxious effects on plant growth and development ultimately affecting the crop productivity. Among various abiotic stresses, cold stress is one of the main environmental stresses that limits the crop productivity and geographical distribution of most valuable crop plants. However, plants show remarkable developmental plasticity to survive in a continually changing environment. Being sessile, plants have generated in the course of their development proficient strategies of tremendous response to elude, tolerate, or adapt to various types of environmental stress conditions including cold. The acclimatization to various abiotic stress factors is largely dependent upon the activation of cascades of molecular channels involved in stress perception, signal transduction, and the expression of specific stress-related genes and metabolites. Understanding the pathway mechanisms by which plants recognize these stress signals and then transduce them to cellular machinery in order to stimulate adaptive responses is of crucial importance to crop biology. Here we summarize cold stress tolerance mechanism pathways in plants. The main significant points discussed in this chapter include (a) adverse effects of cold stress on plant physiochemical parameters, (b) sensing of cold temperature and involvement of various signal transduction pathways, (c) function of various compatible solutes or osmoprotectants, and (d) types and functions of different cold-responsive genes and transcription factors (TFs) involved in various cold stress tolerance mechanisms.

Recent Trends and Approaches in Phytoremediation

The current technique of remediation of heavy metal from contaminated soil is not cost-effective and eco-friendly. Besides, these heavy metals are recalcitrant and are not degraded like organic compounds, therefore effective clean-up requires their immobilization to reduce or remove toxicity. Phytoremediation in future will play an important role in attaining the goals towards sustainable development. The recent development in biotechnology has generated a large knowledge base and thus has opened many opportunities for research and development in the field of phytoremediation. In this chapter we summarize some recent approaches in phytoremediation and how genetic engineering plays an important role to improve the potential of phytoremediation.

Phytoremediation: An Eco-Friendly Green Technology for Pollution Prevention, Control and Remediation

Among the environmental concerns the accumulation of heavy metals is of prime importance. The factors that are generally responsible for deteriorating soil quality include geological and anthropogenic activities. Besides, due to constantly changing urbanization and industrialization patterns the quality of the soil has greatly been affected which ultimately poses a threat to the ecosystem, food safety and human health. Reclamation of these contaminated soils by engineering methods is expensive, time consuming and sometimes not eco-friendly. Researchers all over the world are focusing to exploit the potential of plants as phytoremediators, a technology which is cost-effective, sustainable and eco-friendly. Phytoremediation technology is emerging gradually and as one of the important components of green technology which aims to employ plants across various genera for restoring ecosystem health. Plants possess a natural ability to eliminate, detoxify or immobilize environmental contaminants in a growth matrix by means of various biological processes. The main significant points discussed in this chapter include the mechanisms of phytoremediation and factors affecting phytoremediation.

Plant Signaling: Response to Reactive Oxygen Species

It is noteworthy to mention how the last 20 years have modified the concept of signalling in plants, especially the molecular crosstalk associated with it. Plants have the ability to show remarkable developmental plasticity to sustain in a continually changing environment. In response to various environmental stresses such as drought, salinity, metal toxicity, temperature and pathogens, plants defend themselves by developing some special defence mechanisms. Plants recognise these environmental signals with the help of some membrane protein sensors and then transduce these signals to the nucleus which ultimately stimulates various transcription factors and genes to form the product that ultimately leads to plant adaptation and assists the plant to sustain and surpass the adverse conditions. Amongst the environmental factors which are involved in signalling is the reactive oxygen species (ROS) generated during cell metabolism. ROS are spontaneously produced in the cell enzymatically through the action of various soluble membrane-bound enzymes and nonenzymatically by autoxidation reactions. Some of these ROS (e.g. superoxide dismutase, hydrogen peroxide and nitric oxide) are physiologically useful and in fact necessary for life but can also be harmful if present in excess or in inappropriate amounts. Current research in this regard focuses more on the development of transgenic plants with enhanced tolerance to ROS by using genetic approaches and analytical techniques. In particular nitric oxide (NO), a reactive radical, may be involved in the defence mediated by the ROS such as defence gene activation, hypersensitive response cell death and phytoalexin biosynthesis. By using biotechnological approaches NO together with ROS activates a stronger response and tolerance to various stresses in plants.

Biomass Pellet Technology: A Green Approach for Sustainable Development

The supply of sustainable or green energy is the main challenge that mankind will face over the coming decades, especially because of the need to address climatic changes. Biomass being abundantly available in nature can make a substantial contribution to cater future energy demands in a sustainable way. Currently, it is the largest universal contributor of green energy and has significant potential to expand in the production of electricity, heat and fuels. However, handling as well as direct combustion of biomass is restrained due to peculiar properties of this kind of fuel. As raw biomass possesses low density (30–50 kg/m3) and high moisture content that limits its usage for energy purposes and it needs to be densified prior to its use. The compact and densified biomass possess a high magnitude of density as well as low moisture content which in turn helps to dwindle technical limitations associated with storage, handling and transportation. One immediate solution is the pelletisation of raw biomass that enhances its energy efficiency and enables the competition of biomass with other types of fuels. Besides, biomass pellet technology has gained a rapid momentum in many European countries. The future of the biomass pellet industry is greatly influenced by various environmental, economic, political as well as social aspects that create a multiplex relation among suppliers, producers and consumers. Therefore, the main aim of this chapter is to develop a comprehensive review of biomass processing that involves pellet production technology, energy efficiency of biomass pellet, current status, opportunities and challenges for the development of biomass pellet market.

Plant Rab GTPases in Membrane Trafficking and Signalling

In the eukaryotic systems the membrane trafficking inside the cells is indispensible. The membrane trafficking is a highly regulated process in which various molecular machineries are involved. It involves the vesicle formation, tethering, and finally fusion. According to the phylogenetic analysis, these processes are highly conserved among various organisms. This suggests the acquisition of common ancestral lineages by eukaryotes. In addition, to the similarity in components of trafficking in eukaryotes, each organism has also acquired various specific regulatory molecules which ascertain the diversification to membrane trafficking. In this review we summarize the progress in recent times about the plant-specific Rab GTPases in membrane trafficking events. Rab GTPases are a diverse group which are involved in various processes of membrane trafficking. Further, there are some reports which suggest Rab GTPases’ role in signalling pathways involving light, hormones, biotic, and abiotic stresses. Despite these there is still some inhibition among the scientific community to ascribe the latter roles to Rab GTPases with certainty even though the membrane trafficking events are integrated with signalling.

Lignocellulosic Biomass: As Future Alternative for Bioethanol Production

Biofuels provide a potential and promising green alternative to avoid the global political instability and environmental crises that arise from dependence on petroleum. It has an important role to mitigate global warming and to conserve fossil fuels. Currently, starchy crops such as corn are utilized as a source of raw material for the production of bioethanol but it cannot meet global fuel requirements. Besides, due to their food value these conventional crops are not able to cater the demand of biofuel production. Therefore, lignocellulosic biomass seems to be an attractive alternative for inexorable supplies of biofuels, cutting down the credence on fossil fuel resources. Lignocellulosic biomass feedstock is abundant, recyclable, cheap, and is evenly distributed in nature. However, lignocellulosic bioethanol production is not commercialized at a large scale due to certain economic and technical barriers which make ethanol production exorbitant. Therefore, research should be focussed to develop commercially profitable processes (green technology) for bioethanol production. Moreover, current approach is focussed on enzyme-based conversion of lignocellulosic biomass to bioethanol. The assurance of highly dynamic conversion coupled to a “Green” technology is now universally appealing. Therefore, the main aim of this chapter is to critically analyze the current situation and future needs for technological developments in the area of producing liquid biofuels from lignocellulosic biomass. It primarily covers distinct lignocellulosic biomass conversion technologies, challenges, and future research targets.