Showing papers by "Narendra Tuteja published in 2019"

Field performance of bacterial inoculants to alleviate water stress effects in wheat (Triticum aestivum L.)

Abstract: Plant growth promoting bacteria (PGPB) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase can play an important role in abiotic stress tolerance in plants, particularly drought. The objective of this study was to evaluate bacterial strains Variovorax paradoxus RAA3, Pseudomonas palleroniana DPB16, Pseudomonas sp. UW4 for their ability to alleviate drought stress in wheat in field experiments under irrigated and rain-fed conditions in the Uttarkhand region of India. In this study, ACC deaminase producing bacterial strains Pseudomonas palleroniana DPB16, Pseudomonas sp. UW4 and Variovorax paradoxus RAA3 were evaluated for their efficiency in improving growth, nutrient content and yield of wheat varieties, HD2967 (drought sensitive) and PBW660 (drought tolerant) under rainfed (drought) and irrigated conditions. Bacterial inoculants increased grain and straw yields at both sites, however the response to inoculation was considerably higher under rainfed conditions (64 to 90% increase with inoculation) compared to that observed under irrigated conditions (22 to 40% increase with inoculation). Of the three seed-coated inoculants tested, strain RAA3 maximally improved grain yield (28.2%, 47.4%), straw yield (11.2%, 26.0%) and harvest index (10.6%, 15.3%) under irrigated and rainfed conditions, respectively, compared to non-inoculated crops. The relative expression of the drought responsive gene aquaporin (TaTIP1;1), in response to inoculation, was significantly higher (3.34-fold) in the wheat variety PBW 660, as compared to the drought sensitive variety HD 2967 in which the expression level of aquaporin was unaffected. Under rainfed conditions, the relative mRNA level of the helicase gene WDH45 was significantly higher in HD 2967 (1.54-fold) than the PBW 660 (3.69-fold). Bacterial inoculation caused significant positive changes in plant biochemical and antioxidant properties compared to uninoculated plants. Overall, the results show that the selected PGPB containing ACC deaminase activity along with other plant growth promoting characteristics are effective inoculants for improving wheat yields in irrigated and rainfed field experiments.

Marker-free transgenic rice plant overexpressing pea LecRLK imparts salinity tolerance by inhibiting sodium accumulation.

Abstract: PsLecRLK overexpression in rice provides tolerance against salinity stress and cause upregulation of SOS1 pathway genes, which are responsible for extrusion of excess Na+ ion under stress condition. Soil salinity is one of the most devastating factors threatening cultivable land. Rice is a major staple crop and immensely affected by soil salinity. The small genome size of rice relative to wheat and barley, together with its salt sensitivity, makes it an ideal candidate for studies on salt stress response caused by a particular gene. Under stress conditions crosstalk between organelles and cell to cell response is imperative. LecRLK is an important family, which plays a key role under stress conditions and regulates the physiology of the plant. Here we have functionally validated the PsLecRLK gene in rice for salinity stress tolerance and hypothesized the model for its working. Salt stress sensitive rice variety IR64 was used for developing marker-free transgenic with modified binary vector pCAMBIA1300 overexpressing PsLecRLK gene. Comparison of transgenic and wild-type (WT) plants showed better physiological and biochemical results in transgenic lines with a low level of ROS, MDA and ion accumulation and a higher level of proline, relative water content, root/shoot ration, enzymatic activities of ROS scavengers and upregulation of stress-responsive genes. Based on the relative expression of stress-responsive genes and ionic content, the working model highlights the role of PsLecRLK in the extrusion of Na+ ion from the cell. This extrusion of Na+ ion is facilitated by higher expression of SOS1 (Na+/K+ channel) in transgenic plants as compared to WT plants. Altered expression of stress-responsive genes and change in biochemical and physiological properties of the cell suggests an extensive reprogramming of the stress-responsive metabolic pathways by PsLecRLK under stress condition, which could be responsible for the salt tolerance capability.

Silencing of tomato CTR1 provides enhanced tolerance against Tomato leaf curl virus infection

Abstract: Tomato leaf curl virus (ToLCV) belonging to Begomovirus family of Geminivirus is known to cause one of the most destructive diseases in tomato. Amongst various ToLCVs, a monopartite Tomato leaf curl Joydebpur virus (ToLCJoV) is most prevalent in eastern part of India. In the present study, we observed induced expression of one of the negative regulators of ethylene signaling pathway gene (LeCTR1) in ToLCJoV infected plants. The Tobacco rattle virus (TRV) induced silencing of the LeCTR1 gene provided enhanced tolerance to ToLCJoV infections. The leaf curling as well as ROS accumulation was significantly reduced in the viral infected LeCTR1 silenced plants. Induction of several defense marker genes (NPR1, PR1, PR5, AOS2, EIN2, EIN3 and ERF5) reinforced enhanced tolerance against ToLCJoV infection in the LeCTR1 silenced tomato. Overall, the present study provides evidence that silencing of LeCTR1 can be deployed to protect tomato from ToLCJoV infections.

Concurrent overexpression of rice G-protein β and γ subunits provide enhanced tolerance to sheath blight disease and abiotic stress in rice

Abstract: Our study demonstrates that simultaneous overexpression of RGB1 and RGG1 genes provides multiple stress tolerance in rice by inducing stress responsive genes and better management of ROS scavenging/photosynthetic machineries. The heterotrimeric G-proteins act as signalling molecules and modulate various cellular responses including stress tolerance in eukaryotes. The gamma (γ) subunit of rice G-protein (RGG1) was earlier reported to promote salinity stress tolerance in rice. In the present study, we report that a rice gene-encoding beta (β) subunit of G-protein (RGB1) gets upregulated during both biotic (upon a necrotrophic fungal pathogen, Rhizoctonia solani infection) and drought stresses. Marker-free transgenic IR64 rice lines that simultaneously overexpress both RGB1 and RGG1 genes under CaMV35S promoter were raised. The overexpressing (OE) lines showed enhanced tolerance to R. solani infection and salinity/drought stresses. Several defense marker genes including OsMPK3 were significantly upregulated in the R. solani-infected OE lines. We also found the antioxidant machineries to be upregulated during salinity as well as drought stress in the OE lines. Overall, the present study provides evidence that concurrent overexpression of G-protein subunits (RGG1 and RGB1) impart multiple (both biotic and abiotic) stress tolerance in rice which could be due to the enhanced expression of stress-marker genes and better management of reactive oxygen species (ROS)-scavenging/photosynthetic machinery. The current study suggests an improved approach for simultaneous improvement of biotic and abiotic stress tolerance in rice which remains a major challenge for its sustainable cultivation.

Receptor-Like Kinases Control the Development, Stress Response, and Senescence in Plants

Abstract: Understanding the regulation of growth, development, stress physiology, and senescence are the central issues in plant biology that are controlled through signal transduction pathways. The membrane is the first site of signal perception through receptor proteins. Receptors perceive the signals and initiate cellular signaling through downstream components, including kinases. Plant receptor-like kinases (RLKs) are an example of membrane-embedded, signal-perceiving proteins; they consist of an N-terminal extracellular ligand recognition domain, a central transmembrane domain, and a C-terminal kinase domain. An N-terminal receptor domain is involved in the recognition of specific signals and activation of the kinase domain for signaling further downstream. RLKs are the members of the largest gene family (610 genes in Arabidopsis and 1132 in rice) and have been known to be involved in development, signaling, senescence, and biotic and abiotic stress tolerance. For biotic stress membrane-associated RLKs are involved in pattern recognition receptors (PRRs), reflecting the prevalence of apoplastic colonization of plant-infecting microbes. The hormonal physiology of plants is also controlled by RLKs, as they play a role in a wide variety of signal transduction pathways related to hormone and development. In this chapter, we have reviewed the important studies on RLKs, covering areas of plant physiology such as development, senescence, and responses to biotic and abiotic stress.

Role of Plant Helicases in Imparting Salinity Stress Tolerance to Plants

Abstract: Helicases are motor proteins which possess nucleic acid-binding, NTP binding, and hydrolysis and nucleic acid-unwinding activities. These proteins use their basic biochemical activities to perform various essential cellular functions such as replication, transcription, DNA damage repair, recombination, small RNA biogenesis, translation, and maintenance of genome integrity. Sequence analysis showed the presence of conserved motifs in helicases which help in nucleic acid binding, NTP binding, and hydrolysis and unwinding of duplex structures. Broadly, helicases can be classified as DNA helicase or RNA helicase on the basis of nucleic acid substrate they unwind, but close analysis of sequence and structures resulted in their classification into six superfamilies from SF1 to SF6. In addition, to perform essential basic cellular functions helicases are reported to provide salinity stress tolerance to plants. Salinity is one of the disastrous abiotic stresses of plants which in extreme conditions causes the death of plant. PDH45 was the first helicase isolated from Pisum sativum that provided salinity stress tolerance in plants. Various labs from all over the world reported different helicases which play key roles in providing salinity stress tolerance in various economically important crops. Helicases being motor protein and involved in gene expression are reported to be involved in improving the photosynthetic machinery, modulation of antioxidant machinery, pre-mRNA splicing and small regulatory RNA biogenesis. Helicases have been ignored in plants for a very long time, but recent research in this field opens great opportunities to use this class of protein for making salinity-tolerant crops to overcome the issue of saline soil globally.

Cyanide produced with ethylene by ACS and its incomplete detoxification by β-CAS in mango inflorescence leads to malformation

Abstract: Malformation of mango inflorescences (MMI) disease causes severe economic losses worldwide. Present research investigates the underlying causes of MMI. Results revealed significantly higher levels of cyanide, a by-product of ethylene biosynthesis, in malformed inflorescences (MI) of mango cultivars. There was a significant rise in ACS transcripts, ACS enzyme activity and cyanide and ethylene levels in MI as compared to healthy inflorescences (HI). Significant differences in levels of methionine, phosphate, S-adenosyl-L-methionine, S-adenosyl-L-homocysteine, ascorbate and glutathione, and activities of dehydroascorbate reductase and glutathione reductase were seen in MI over HI. Further, a lower expression of β-cyanoalanine synthase (β-CAS) transcript was associated with decreased cellular β-CAS activity in MI, indicating accumulation of unmetabolized cyanide. TEM studies showed increased gum-resinosis and necrotic cell organelles, which might be attributed to unmetabolized cyanide. In field trials, increased malformed-necrotic-inflorescence (MNI) by spraying ethrel and decreased MNI by treating with ethylene inhibitors (silver and cobalt ions) further confirmed the involvement of cyanide in MMI. Implying a role for cyanide in MMI at the physiological and molecular level, this study will contribute to better understanding of the etiology of mango inflorescence malformation, and also help manipulate mango varieties genetically for resistance to malformation.

Pea p68, a DEAD-box helicase, enhances salt tolerance in marker-free transgenic plants of soybean [Glycine max (L.) Merrill].

Abstract: Protein p68 is a prototype constituent of DEAD-box protein family, which is involved in RNA metabolism, induced during abiotic stress conditions. In order to address the salinity stress faced by economically important soybean crop, we have transformed soybean cv. PUSA 9712 via direct organogenesis with marker free construct of p68 gene by Agrobacterium-mediated genetic transformation. The putative transgenic plants were screened by Polymerase chain reaction (PCR), Dot blot analysis and Southern blot hybridization. Reverse transcriptase-PCR (RT-PCR) and Quantitative real-time PCR (qRT-PCR) established that the p68 gene expressed in three out of five southern positive (T1) plants. The transformed (T1) soybean plants survived irrigation upto 200 mM of NaCl whereas the non-transformed (NT) plants could not survive even 150 mM NaCl. The transgenic soybean (T1) plants showed a higher accumulation of chlorophyll, proline, CAT, APX, SOD, RWC, DHAR and MDHAR than the NT plants under salinity stress conditions. The transformed (T1) soybean plants also retained a higher net photosynthetic rate, stomatal conductance and CO2 assimilation as compared to NT plants. Further analysis revealed that (T1) soybean plants accumulated higher K+ and lower Na+ levels than NT plants. Yield performance of transformed soybean plants was estimated in the transgenic green house under salinity stress conditions. The transformed (T1) soybean plants expressing the p68 gene were morphologically similar to non-transformed plants and produced 22–24 soybean pods/plant containing 8–9 g (dry weight) of seeds at 200 mM NaCl concentration. The present investigation evidenced the role of the p68 gene against salinity, by enhancing the tolerance towards salinity stress in soybean plants.

An Overview of AAA+ Superfamily Proteins Associated Helicases

Abstract: ATPases associated with various cellular functions (AAA+) superfamily is a group of various ATPases associated with diverse cellular functions and have multiple subcellular localizations. Members of this superfamily possess ATPase activity to perform various cellular activities. Sequence information showed the presence of four major conserved motifs—Walker A, Walker B, Sensor I, and Sensor II–involved in ATPase binding and hydrolysis. On the basis of sequence and structural information AAA+ superfamily members are divided into five major groups: Extended AAA, Helicase and Clamp loader (HEC), the Protease, chelatase, transcriptional activators and transport (PACTT), ExeA, and the signal transduction ATPases with numerous domains (STAND). Although, majorly the members of AAA+ superfamily members have only ATPase activity, but a few members also possess helicase activity and these members have been kept in the HEC group. RuvB is the highly conserved member of AAA+ superfamily that has been kept in the HEC group for prokaryotic homolog and in extended AAA group for eukaryotic homologs. RuvB/RuvB-like homologs are involved in multiple functions such as chromatin remodeling, transcription, cell cycle progression, homologous recombination, DNA damage repair mechanism, and chaperon activity. This protein is a major target for drugs against malarial parasites and is also studied in plants (Arabidopsis and rice) as a major stress-responsive gene that can be used to produce stress-tolerant plants.

Flower Senescence: Present Status and Future Aspects

Abstract: Depending on plant species, floral senescence varies. It can be seen in the form of wilting or withering. Both of these results correspond to different physiological phenomena. While wilting happens due to loss of turgor pressure, it corresponds to a slow dehydration process and a change in color. Most of the flower senescence corresponds to petal senescence, where the petals get detached from the plants. The time gap from the onset of senescence until its visible symptoms varies profusely among species to species. In this chapter, we have emphasized the various events that occur during flower senescence, which include structural changes, oxidative changes, and changes at the level of nucleic acids and proteins.

Evolution of RNA Helicases in Plants: Molecular and Functional Insights

Abstract: Helicases are an ubiquitous, highly diverse group of proteins that perform a variety of functions in cells. RNA helicases are a large group of enzymes that function in virtually all aspects of RNA metabolism. Although RNA helicases share a highly conserved structure, different enzymes display a wide array of biochemical activities, including RNA duplex unwinding, protein displacement from RNA, and strand annealing. DEAD-box RNA helicases, which also comprise a large family, are also involved in a range of RNA processing events. Since their discovery as nucleic acid unwinding enzymes, emerging new roles in plant-stress biology has led to identifying the source of diversity they possess. On studying their similarity, their helicase core was found to be very conserved. The diverse functions could be the attribute of other motifs present in them. In this chapter, we try to link helicases’ phylogeny with their expression profiling in the plant kingdom.