Showing papers by "Narendra Tuteja published in 2018"

Targeting the Redox Regulatory Mechanisms for Abiotic Stress Tolerance in Crops

Abstract: Abiotic stress impacts on plants are inevitable, and are mainly the result of impairments in cellular redox homeostasis. In fact, abiotic stress-provoked elevations in reactive oxygen species (ROS) are the main driver of cellular redox homeostasis. In addition to reviewing ROS, their chemistry, and sites of production; this chapter highlights the dual roles of ROS in separate sections, and discusses in detail the role and modulation of major enzymatic and nonenzymatic components of antioxidant defense systems involved in cellular redox regulation in abiotic-stressed plants.

Microbe-Mediated Enhancement of Nitrogen and Phosphorus Content for Crop Improvement

Abstract: The uncontrolled increase in the global population, the increasing demand of food, and a rapidly changing environment have caused a major decrease in the agricultural productivity. Sooner or later, it would be impossible to feed such a large population because of these persisting problems. The situations sometimes become worse as plants have to inadvertently face abiotic and biotic environmental stresses, two major concerns for decreased food productivity. Plants, being sessile in nature, must acquire the essential nutrients including macro- and micronutrients from the soil. The problem is further exacerbated due to low efficiency of uptake of important macronutrients by roots in plant that is generally countered by increasing the fertilizer dosage. However, the extensive overuse of these chemical supplements in the form of fertilizers might cause unexpected environmental constraints. Plants are routinely confronted with nutrient deficiency from the ever depleting soil systems and their immediate environment year after year. Therefore, the current plateau in agricultural productivity is a result of higher usage of chemical fertilizers. Nevertheless, the high dosage of these fertilizers has become an essential component of day-to-day agriculture as they supply essential plant nutrients like nitrogen, phosphorus, and potassium to the developing crops. Indeed, projected food demand for the growing population by 2050 would require a much higher dose of chemical fertilizers but shall negatively affect the soil properties. Conversely, more than half of the applied nitrogen and phosphorous can be lost from the fertile agricultural lands where nitrogen can be lost in the form of N2, trace gases, and nitrates that are leached into the soil, and phosphorous could be lost up to 90% by forming metal complexes in the soil.

Stress-induced Oryza sativa RuvBL1a is DNA-independent ATPase and unwinds DNA duplex in 3′ to 5′ direction

Abstract: RuvB, a member of AAA+ (ATPases Associated with diverse cellular Activities) superfamily of proteins, is essential, highly conserved and multifunctional in nature as it is involved in DNA damage repair, mitotic assembly, switching of histone variants and assembly of telomerase core complex. RuvB family is widely studied in various systems such as Escherichia coli, yeast, human, Drosophila, Plasmodium falciparum and mouse, but not well studied in plants. We have studied the transcript level of rice homologue of RuvB gene (OsRuvBL1a) under various abiotic stress conditions, and the results suggest that it is upregulated under salinity, cold and heat stress. Therefore, the OsRuvBL1a protein was characterized using in silico and biochemical approaches. In silico study confirmed the presence of all the four characteristic motifs of AAA+ superfamily-Walker A, Walker B, Sensor I and Sensor II. Structurally, OsRuvBL1a is similar to RuvB1 from Chaetomium thermophilum. The purified recombinant OsRuvBL1a protein shows unique DNA-independent ATPase activity. Using site-directed mutagenesis, the importance of two conserved motifs (Walker B and Sensor I) in ATPase activity has been also reported with mutants D302N and N332H. The OsRuvBL1a protein unwinds the duplex DNA in the 3' to 5' direction. The presence of unique DNA-independent ATPase and DNA unwinding activities of OsRuvBL1a protein and upregulation of its transcript under abiotic stress conditions suggest its involvement in multiple cellular pathways. The first detailed characterization of plant RuvBL1a in this study may provide important contribution in exploiting the role of RuvB for developing the stress tolerant plants of agricultural importance.

In Planta transformation for conferring salt tolerance to a tissue-culture unresponsive indica rice (Oryza sativa L.) cultivar

Abstract: Many farmer-popular indica rice (Oryza sativa L.) cultivars are recalcitrant to Agrobacterium-mediated transformation through tissue culture and regeneration. In planta transformation using Agrobacterium could therefore be a useful alternative for indica rice. A simple and reproducible in planta protocol with higher transformation efficiencies than earlier reports was established for a recalcitrant indica rice genotype. Agrobacterium tumefaciens containing the salt tolerance-enhancing Pea DNA Helicase45 (PDH45) gene, with the reporter and selectable marker genes, gus-INT (β-glucuronidase with intron) and hygromycin phosphotransferase (hpt), respectively, were used. Overnight-soaked mature embryos were infected and allowed to germinate, flower, and set T1 seeds. T0 plants were considered positive for the transgene if the spikelets of one or more of their panicles were positive for gus. Thereafter, selection at T1 was done by germination in hygromycin and transgenic status re-confirmation by subjecting plantlet DNA/RNA to gene-specific PCR, Southern and semi-quantitative RT-PCR. Additionally, physiological screening under saline stress was done at the T2 generation. Transformation efficiency was found to be 30–32% at the T0 generation. Two lines of the in planta transformed seedlings of the recalcitrant rice genotype were shown to be saline tolerant having lower electrolyte leakage, lower Na+/K+, minimal leaf damage, and higher chlorophyll content under stress, compared to the WT at the T2 generation.

Helicases and Their Importance in Abiotic Stresses

Abstract: Helicases are a ubiquitous class of ATP-dependent nucleic acid unwinding enzymes crucial for life processes in all living organisms. There are six classes of helicases based on their conserved amino acid sequences. All eukaryotic RNA helicases belong to the SF1 and SF2 groups. Groups SF3–SF5 are mainly viral and bacterial DNA helicases, while SF6 includes the ubiquitous mini-chromosome maintenance or MCM group of helicases. SF3–SF6 are also characterized as hexameric ring-forming, whereas SF1 and SF2 groups are usually monomeric. The SF2 class is the largest group of helicases, including both DNA and RNA helicases with the widest range of function in replication, transcription, translation, repair, as well as chromatin remodeling. There is no clear sequence-based separation between DNA and RNA helicases. SF2 also includes both RNA and DNA helicases that are involved in biotic and abiotic stresses. While both DNA and RNA helicases play important roles in normal cellular function, the latter are more markedly involved in stress alleviation. This functional divergence was also evident in promoter sequence comparisons of the 113 A. thaliana helicases. Some DNA helicases like those from SF6 (MCM) and SF2 (CHR) are also active under stressed conditions. However, the most prominent stress-activated helicases are those with the conserved amino acid motifs, DEAD/H. Overexpression of DEAD/H helicases in many crops confers a growth advantage in the transgenic plants and has resulted in their protection against major abiotic stresses, such as salinity, drought, and oxidative stresses with minimal loss in yield potential.

Introgression, Generational Expression and Salinity Tolerance Conferred by the Pea DNA Helicase 45 Transgene into Two Commercial Rice Genotypes, BR28 and BR47

Abstract: DNA helicase (PDH45) from the pea plant (Pisum sativum) is a member of the DEAD box protein family and plays a vital regulatory role in saline stress tolerance in plants. We previously reported that over-expression of PDH45 gene confers both seedling and reproductive stage salinity tolerance to a Bangladeshi rice landrace, Binnatoa (BA). In this study, transgenic BA-containing PDH45 (♂) was crossed with two different farmer-popular BRRI rice varieties (♀), BR28 and BR47, in a contained net house. F1 plants positive for the transgene and having recipient phenotype were advanced from F1 to F5. Expression of the PDH45 gene was detected in all generations. The expression level of PDH45 was 200-fold higher in the donor compared to the two recipient genotypes but without any effect on their salt stress tolerance ability in various assays. Under 120 mM NaCl stress at seedling stage, all rice genotypes showed vigorous growth, higher chlorophyll content, lower electrolyte leakage and lower LDS (Leaf Damage Score) compared to their corresponding wild types. At the reproductive stage under continuous salinity stress at 80 mM NaCl, the cross-bred lines BR28 and BR47 showed significantly better spikelet fertility and yield per plant, which were two- and 2.5-folds, respectively, than their corresponding wild types. The PDH45 transgene was observed to increase the expression of 6 salt stress-related downstream genes at 150 mM NaCl stress to similar differential degrees in the donor and recipient genotypes. However, the expression of OsLEA was significantly higher in transgenic BR28 compared to transgenic BR47, where the latter shows comparatively higher salt tolerance. The study shows stability of transgene expression across generations. It also demonstrates that there may be an effect of background genotype on transgene expression. Moreover, some downstream effects of the transgene may also be genotype-specific.

DNA Helicase-Mediated Abiotic Stress Tolerance in Plants

Abstract: DNA helicases are also called molecular motors. They unwind the DNA with the help of ATP hydrolysis, and thus facilitate the replication and transcription processes. In addition to the general functions of DNA helicases in DNA replication, DNA repair and recombination, chromosome segregation, and transcription initiation; a number of other processes that are controlled by DNA helicases have recently been discovered. Studies have suggested that DNA helicases may play a role in plant DNA recombination, as it is prominent during the meiotic prophase of plants. Many aspects of DNA helicases have yet to be studied. Some of these are the structural biology of the different helicases, the molecular mechanisms that specify their cellular functions, and so forth. In this chapter, we have summarized some of the studies on plant DNA helicases, such as PDH45, KU, SUV3, XPB, XPD, nucleolin, and mini-chromosome maintenance proteins. The role of plant DNA helicases in abiotic stress tolerance is also discussed.