Search results for: abiotic stress

Authors: Zemour Kamel, Chouhim Kadda Mohamed Amine

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Salinity is one of the most environmental factors limiting crop productivity. It has a negative effect on both germination and plant growth processes (photosynthesis, respiration, and transpiration), nutrient balance, membrane properties and cellular homeostasis, enzymatic and metabolic activities. Among the strategic crops in the world and more mainly in Algeria, durum wheat is very affected by this abiotic stress. For that, this study focuses on an evaluation of salt stress effect on the germination process of durum wheat as well as its response after application of lavender hydrosol and aqueous pistachio extract. The results have shown that all the physicochemical parameters of germination have been affected by this stress. However, lavender hydrosol and aqueous pistachio extract, considered as organic compounds, significantly improved the germination of wheat seeds. Finally, this study has highlighted the importance of using organic products as an ideal alternative to reduce the effect of abiotic stress on durum wheat productivity.

Keywords: salinity, wheat durum, extract, lavender hydrosol, aqueous pistachio

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Authors: Taoufik Bettaieb, Sihem Soufi

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As a bioactive metalloid, silicon (Si) is an essential element for plant growth and development. It also plays a crucial role in enhancing plants’ resilience to different abiotic and biotic stresses. The morpho-physiological, biochemical, and molecular background of Si-mediated stress tolerance in plants were unraveled. Cold stress is a severe abiotic stress response to the decrease of plant growth and yield by affecting various physiological activities in plants. Several approaches have been used to alleviate the adverse effects generated from cold stress exposure, but the cost-effective, environmentally friendly, and defensible approach is the supply of silicon. Silicon has the ability to neutralize the harmful impacts of cold stress. Therefore, based on these hypotheses, this study was designed in order to investigate the morphological and physiological background of silicon effects applied at different concentrations on cold stress mitigation during early growth of a turfgrass, namely Paspalum vaginatum Sw. Results show that silicon applied at different concentrations improved the morphological development of Paspalum subjected to cold stress. It is also effective on the photosynthetic apparatus by maintaining stability the photochemical efficiency. As the primary component of cellular membranes, lipids play a critical function in maintaining the structural integrity of plant cells. Silicon application decreased membrane lipid peroxidation and kept on membrane frontline barrier relatively stable under cold stress.

Keywords: crops, cold stress, silicon, abiotic stress

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Authors: Deepak Bhardwaj, Narendra Tuteja

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Global climate change is impacting large agrarian societies, especially those in countries located near the equator. Agriculture, and consequently, plant-based food, is the hardest hit in tropical and sub-tropical countries such as India due to an increased incidence of drought as well as an increase in soil salinity. One method that holds promise is AMF-rich biofertilizers which assist in activating proteins which in turn help alleviate abiotic stress in plants. In the present study, we identified two important species of (arbuscular mycorrhizal fungus) AMF belonging to Glomus and Gigaspora from the rhizosphere of the important medicinal plant Justicia adathoda. These two species have been found to be responsible for the abundance of Justicia adathoda in the semi-arid areas of the Jammu valley located in northern India, namely, the Union Territory of Jammu and Kashmir. We isolated the species of Glomus and Gigaspora from the rhizosphere of Justicia adathoda and used them as biofertilizers for the tomato plant. Significant improvements in the growth parameters were observed in the tomato plants inoculated with Glomus sp. and Gigaspora sp. in comparison with the tomato plants that were grown without AMF treatments. Tomato plants grown along with Glomus sp. and Gigaspora sp. have been observed to withstand 200 mM of salinity and 25% PEG stress. AMF also resulted in an increased concentration of proline and antioxidant enzymes in tomato plants. We also examined the expression levels of salinity and drought stress-inducible genes such as pea DNA helicase 45 (PDH 45) and genes of G-protein subunits of the tomato plants inoculated with and without AMF under stress and normal conditions. All the stress-inducible genes showed a significant increase in their gene expression under stress and AMF inoculation, while their levels were found to be normal under AMF inoculation without stress. We propose a model of abiotic stress alleviation in tomato plants with the help of external factors such as AMF and internally with the help of proteins like PDH 45 and G-proteins.

Keywords: AMF, abiotic stress, g-proteins, PDH-45

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Authors: Zia Ullah, Muhammad Asim, Shi Sujuan, Rayyan Khan, Aaqib Shaheen, LIU Haobao

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The plant-specific auxin efflux proteins PIN-FORMED (PIN) have been well depicted in many plant species for their essential roles in regulating the transport of auxins in several phases of plant growth. Little is known about the various functions of the PIN family genes in the Nicotiana tabacum (N. tabacum) species during plant growth. To define the expression pattern of the NtPIN1a gene under abiotic stresses and hormone treatment, transgenic tobacco with promoterNtPIN1a::GUS construct was employed. Comprehensive computational analyses of the NtPIN1a promoter confirmed the existence of common core promoter elements including CAAT-box, TATA-box, hormone, and abiotic stress-responsive elements such as ABRE, P-box, MYC, MYB, ARE, and GC-motifs. The transgenic plants with the promoter of NtPIN1a displayed a promising expression of β-glucuronidase (GUS) in germinating seeds, root tips, shoot-apex, and developing leaves under optimal conditions. While the differential expression of GUS in moderate salt, drought, low potassium stresses, and externally high auxin level at two different time points, suggested NtPIN1a played a key role in growth processes and the plants’ response to abiotic stresses. This analysis provides a foundation for more in-depth discoveries of the biological functions of NtPIN1a in Nicotiana species and this promoter may be employed in genetic engineering of other crops for enhanced stress tolerance.

Keywords: tobacco, nicotiana tabacum, pin, promoter, GUS, abiotic stresses, auxin

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Authors: Iman Kamranfar, Gang-Ping Xue, Salma Balazadeh, Bernd Mueller-Roeber

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Adverse environmental conditions such as salinity stress, high temperature and drought limit plant growth and typically lead to precocious tissue degeneration and leaf senescence, a process by which nutrients from photosynthetic organs are recycled for the formation of flowers and seeds to secure reaching the next generation under such harmful conditions. In addition, abiotic stress affects developmental patterns that help the plant to withstand unfavourable environmental conditions. We discovered an NAC (for NAM, ATAF1, 2, and CUC2) transcription factor (TF), called RAF in the following, which plays a central role in abiotic drought stress-triggered senescence and the control of developmental adaptations to stressful environments. RAF is an ABA-responsive TF; RAF overexpressors are hypersensitive to abscisic acid (ABA) and exhibit precocious senescence while knock-out mutants show delayed senescence. To explore the RAF gene regulatory network (GRN), we determined its preferred DNA binding sites by binding site selection assay (BSSA) and performed microarray-based expression profiling using inducible RAF overexpression lines and chromatin immunoprecipitation (ChIP)-PCR. Our studies identified several direct target genes, including those encoding for catabolic enzymes acting during stress-induced senescence. Furthermore, we identified various genes controlling drought stress-related developmental changes. Based on our results, we conclude that RAF functions as a central transcriptional regulator that coordinates developmental programs with stress-related inputs from the environment. To explore the potential agricultural applications of our findings, we are currently extending our studies towards crop species.

Keywords: abiotic stress, Arabidopsis, development, transcription factor

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Authors: Faiza Ateeq, Huma Jawed, Kamran Azim, Nadeem Khalid

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Abiotic constraints such as salinity stress reduce cereal production. Salicylic acid is an elicitor of abiotic stress tolerance in plants. The aim of this study was to investigate the effects of salicylic acid on bread wheat cultivars AAI_10 from Faisalabad, Pakistan (Triticum aestivum L.) grown under salt stress in the presence and absence of 0.5 mM salicylic acid. The Physiological test was performed using different concentrations of salt solutions, i.e., 0%, 1%, 2%, 4%, and 6% on leaf blades, and determined the germination of seedlings growth after 14 days. Results showed a reduction in the weights of wheat seedlings when it’s dry and fresh in the consideration of salt stress. Salicylic Acid treatment has a positive effect when evaluated in the case of salt-treated control. The morphological test (Lowry method) was performed to determine the concentration of proteins in different samples. Results showed that the samples treated with SA showed the highest absorbance(720nm) as compared to the control and other treated samples absorbance was determined. Thus, Salicylic Acid treating wheat seedlings enables the growth of anti-stress effects, such as maintaining proline accumulation. The morphological and physiological parameters revealed that SA treatment not only decreased the negative effect of salinity on the development of the seedlings but also accelerated the reparation of the growth processes. These results suggested that salicylic acid application improved the salt tolerance of bread wheat cultivars.

Keywords: salinity, salicylic acid, biotic and abiotic stresses, proline

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Authors: Azhar Alhasawi, Vasu D. Appanna

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Chitin, the second most abundant bio-polymer in nature after cellulose, composed of β (1→4) linked N-acetylglucosamine (GlcNAc), is a major structural component in the cell walls of fungi and the shells of crustaceans. Chitin and its derivatives are gaining importance of economic value due to its biological activity and its industrial and biomedical applications. There are several methods to hydrolyze chitin to NAG, but they are typically expensive and environmentally unfriendly. Chitinase which catalyzes the breakdown of chitin to NAG has received much attention owing to its various applications in biotechnology. The presented research examines the ability of the versatile soil microbe, Pseudomonas fluorescens grown in chitin medium to produce chitinase and a variety of value-added products under abiotic stress. We have found that with high pH, Pseudomonas fluorescens enable to metabolize chitin more than with neutral pH and the overexpression of chitinase was also increased. P-dimethylaminobenzaldehyde (DMAB) assay for NAG production will be monitored and a combination of sodium dodecyl polyacrylamide gels will be used to monitor the proteomic and metabolomic changes as a result of the abiotic stress. The bioreactor of chitinase will also be utilized.

Keywords: Pseudomonas fluorescens, chitin, DMAB, chitinase

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Authors: Nurul Aliaa Idris, David A. Collings

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Phi thickenings are specialized secondary cell wall thickenings that are found in the cortex of the roots in a wide range of plant species, including orchids. The role of phi thickenings in the root is still under debate through research have linked environmental conditions, particularly abiotic stresses such as water stress, heavy metal stress and salinity to their induction in the roots. It has also been suggested that phi thickenings may act as a barrier to regulate solute uptake, act as a physical barrier against fungal hyphal penetration due to its resemblance to the Casparian strip and play a mechanical role to support cortical cells. We have investigated phi thickening function in epiphytic orchids of the genus Miltoniopsis through induction experiment against factors such as soil compaction and water stress. The permeability of the phi thickenings in Miltoniopsis was tested through uptake experiments using the fluorescent tracer dyes Calcofluor white, Lucifer yellow and Propidium iodide then viewed with wide-field or confocal microscopy. To test whether phi thickening may prevent fungal colonization in the root cell, fungal re-infection experiment was conducted by inoculating isolated symbiotic fungus to sterile in vitro Miltoniopsis explants. As the movement of fluorescent tracers through the apoplast was not blocked by phi thickenings, and as phi thickenings developed in the roots of sterile cultures in the absence of fungus and did not prevent fungal colonization of cortical cells, the phi thickenings in Miltoniopsis do not function as a barrier. Phi thickenings were found to be absent in roots grown on agar and remained absent when plants were transplanted to moist soil. However, phi thickenings were induced when plants were transplanted to well-drained media, and by the application of water stress in all soils tested. It is likely that phi thickenings stabilize the root cortex during dehydration. Nevertheless, the varied induction responses present in different plant species suggest that the phi thickenings may play several adaptive roles, instead of just one, depending on species.

Keywords: abiotic stress, Miltoniopsis, orchid, phi thickening

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Authors: A. Bahieldin, A. Atef, S. Edris, N. O. Gadalla, S. M. Hassan, M. A. Al-Kordy, A. M. Ramadan, A. S. M. Al- Hajar, F. M. El-Domyati

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The idea of this work is based on a natural exciting phenomenon suggesting that suppression of genes related to the program cell death (or PCD) mechanism might help the plant cells to efficiently tolerate abiotic stresses. The scope of this work was the detection of PCD-related transcription factors (TFs) that might also be related to salt stress tolerance in plant. Two model plants, e.g., tobacco and Arabidopsis, were utilized in order to investigate this phenomenon. Occurrence of PCD was first proven by Evans blue staining and DNA laddering after tobacco leaf discs were treated with oxalic acid (OA) treatment (20 mM) for 24 h. A number of 31 TFs up regulated after 2 h and co-expressed with genes harboring PCD-related domains were detected via RNA-Seq analysis and annotation. These TFs were knocked down via virus induced gene silencing (VIGS), an RNA interference (RNAi) approach, and tested for their influence on triggering PCD machinery. Then, Arabidopsis SALK knocked out T-DNA insertion mutants in selected TFs analogs to those in tobacco were tested under salt stress (up to 250 mM NaCl) in order to detect the influence of different TFs on conferring salt tolerance in Arabidopsis. Involvement of a number of candidate abiotic-stress related TFs was investigated.

Keywords: VIGS, PCD, RNA-Seq, transcription factors

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Authors: Astghik R. Sukiasyan

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Under the drought stress condition, the plants would grow slower. Temperature is one of the most important abiotic factors which suppress the germination processes. However, the processes of transpiration are regulated directly by the cell water, which followed to an increase in volume of vacuoles. During stretching under the influence of water pressure, the cell goes into the state of turgor. In our experiments, lines of the semi-dental sweet maize of Armenian population from various zones of growth under mild and severe drought stress were tested. According to results, the value of the water balance of the plant cells may reflect the ability of plants to adapt to drought stress. It can be assumed that the turgor allows evaluating the number of received dissolved substance in cell.

Keywords: turgor, drought stress, plant growth, Armenian Zea Maize Semidentata

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Authors: H. Sakamoto, S. Kurosawa, M. Suzuki, S. Oguri

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In Arabidopsis, several genes encoding proteins with ankyrin repeats and trans-membrane domains (AtANKTM) have been identified as mediators of biotic and abiotic stress responses. It has been known that the expression of an AtANKTM gene, At2g24600, is induced in response to abiotic stress and that there are four splicing variants derived from this locus. In this study, by RT-PCR and sequencing analysis, an unknown splicing variant of the At2g24600 transcript was identified. Based on differences in the predicted amino acid sequences, the five splicing variants are divided into three groups. The three predicted proteins are highly homologous, yet have different numbers of ankyrin repeats and trans-membrane domains. It is generally considered that ankyrin repeats mediate protein-protein interaction and that the number of trans-membrane domains affects membrane topology of proteins. The protein variants derived from the At2g24600 locus may have different molecular functions each other.

Keywords: alternative splicing, ankyrin repeats, trans-membrane domains, arabidopsis

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Authors: Rizwan Alam, Ikhtiar Khan, Aqib Iqbal

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Plants are naturally exposed to a wide variety of environmental stresses. The stresses may be biotic or/and abiotic. These environmental stresses have adverse effects on photosynthesis, water relation and nutrients uptake of plants. Fertilization of plants with exogenous minerals can enhance the drought tolerance in plants. In this experiment, canola (Brassica napus) was treated with solutions of calcium nitrate in different concentrations before the imposition of drought stress for 10 days. It was observed that drought stress decreased the tissue-K, Ca and K/Ca ratio of canola seedlings. The tissue-carbon and nitrogen contents were also depressed by the drought stress. Application of calcium nitrate, however, could alleviate the adverse effects of drought stress by showing a positive effect on all the aforementioned parameters.

Keywords: Brassica napus, calcium, carbon, potassium

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Authors: Sobia Shafqat, Saeed Ahmad Qaisrani

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MicroRNAs play an essential role in the regulation and development of all processes in most eukaryotes because of their prospective part as mediators controlling cell growth and differentiation towards the exact position of RNAs response in plants under biotic and abiotic factors or stressors. In a few cases, Zn is oblivious poisonous for plants due to its heavy metal status. Some other metals are extremely toxic, like Cd, Hg, and Pb, but these elements require in rice for the programming of genes under abiotic stress resembling Zn stress when micro RNAs268 was importantly introduced in rice. The micro RNAs overexpressed in transgenic plants with an accumulation of a large amount of melanin dialdehyde, hydrogen peroxide, and an excessive quantity of Zn in the seedlings stage. Let out results for rice pliability under Zn stress micro RNAs act as negative controllers. But the role of micro RNA268 act as a modulator in different ecological condition. It has been explained clearly with a long understanding of the role of micro RNA268 under stress conditions; pliability and practically showed outcome to increase plant sufferance under Zn stress because micro RNAs is an intervention technique for gene regulation in gene expression. The proposed study was experimented with by using genetic factors of Zn stress and toxicity effect on rice plants done at District Vehari, Pakistan. The trial was performed randomly with three replications in a complete block design (RCBD). These blocks were controlled with different concentrations of genetic factors. By overexpression of micro RNA268 rice, seedling growth was not stopped under Zn deficiency due to the accumulation of a large amount of melanin dialdehyde, hydrogen peroxide, and an excessive quantity of Zn in their seedlings. Results showed that micro RNA268 act as a negative controller under Zn stress. In the end, under stress conditions, micro RNA268 showed the necessary function in the tolerance of rice plants. The directorial work sketch gave out high agronomic applications and yield outcomes in rice with a specific amount of Zn application.

Keywords: micro RNA268, zinc, rice, agronomic approach

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Authors: Astghik R. Sukiasyan

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The semidental sweet maize of Armenian population under drought stress and pollution by some heavy metals (HMs) in sites along the river Debet was studied. Accordingly, the objective of this work was to investigate the antioxidant status of maize plant in order to identify simple and reliable criteria for assessing the degree of adaptation of plants to abiotic stress of drought and HMs. It was found that in the case of removal from the mainstream of the river, the antioxidant status of the plant varies. As parameters, the antioxidant status of the plant has been determined by the activity of malondialdehyde (MDA) and Ferric Reducing Ability of Plasma (FRAP), taking into account the characteristics of natural drought of this region. The possibility of using some indicators which characterized the antioxidant status of the plant was concluded. The criteria for assessing the extent of environmental pollution could be HMs. This fact can be used for the early diagnosis of diseases in the population who lives in these areas and uses corn as the main food.

Keywords: antioxidant status, maize corn, drought stress, heavy metal

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Authors: S. Mamoucha, N. Tsafantakis, Α. Ioannidis, S. Chatzipanagiotou, C. Nikolaou, L. Skaltsounis, N. Fokialakis, N. Christodoulakis

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Introduction: Plant secondary metabolites (SM) can be grouped into three chemically distinct groups: terpenes, phenolics, and nitrogen-containing compounds. For many years the adaptive significance of SM was unknown. They were thought to be functionless end-products. Currently it is accepted that many secondary metabolites (also known as natural products) have important ecological roles in plants. For instance, they serve as attractants (odor, color, taste) for pollinators and seed-dispersing animals. Moreover, they protect plants from herbivores, microbial pathogens and from environmental stress (high and low temperatures, drought, alkalinity, salinity, radiation etc). It is well known that both biotic and abiotic stress often increase the accumulation of SM. The local climatic conditions, seasonal changes, external factors such as light, temperature, humidity affect the biosynthesis and composition of secondary metabolites. A well known dioecious evergreen plant, Pistacia lentiscus L. (mastic tree), was selected in order to study the metabolic variations occur in response to the different climate conditions, due to the seasonal variation and its effect on the biosynthesis of bioactive compounds. Materials-methods: Young and mature leaves were collected in January and July 2014, dried and extracted by accelerated solvent extraction (Dionex ASE™ 350) using solvents of increased polarity (DCM, MeOH, and H2O). GC-MS and UHPLC-HRMS analysis were carried out in order to define the nature and the relative abundance of SM. The antibacterial activity was evaluated by using the Agar Disc Diffusion Assay against ATCC and clinical isolates strains: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Streptococcus mutans and Klebsiella pneumoniae. All tests were carried out in duplicate and the average radii of the inhibition zones were calculated for each extract. Results: According to the phytochemical profile obtained from each extract, the biosynthesis of SM varied both qualitatively and quantitatively under the two different types of seasonal stress. With exception of the biologically inactive nonpolar DCM extract of July, all extracts inhibited the growth of most of the investigated microorganisms. A clear positive correlation has been observed between the relative abundance of SM and the bioactivity of the DCM extracts of January and July. Observed changes during phytochemical analysis were mainly focused on the triterpenoid content. On the other hand, the bioactivity of the polar extracts (MeOH and H2O) of January and July resulted practically invariable against most of the microorganisms, besides the significant variation of the SM content due to the seasonal variation. Conclusion: Our results clearly confirmed the hypothesis of abiotic stress as an important regulating factor that significantly affects the biosynthesis of secondary metabolites and thus the presence of bioactive compounds. Acknowledgment: This work was supported by IKY - State Scholarship Foundation, Athens, Greece.

Keywords: antibacterial screening, phytochemical profile, Pistacia lentiscus, abiotic stress

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Authors: Judith Mogouong, Philippe Constant, Robert Lavallee, Claude Guertin

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The emerald ash borer (EAB) is an exotic wood borer insect native from China, which is associated with important environmental and economic damages in North America. Beetles are known to be vectors of microbial communities related to their adaptive capacities. It is now established that environmental stress factors may induce physiological events on the host trees, such as phytochemical changes. Consequently, that may affect the establishment comportment of herbivorous insect. Considering the number of insects collected on ash trees (insects’ density) as an abiotic factor related to stress damage, the aim of our study was to explore the dynamic of EAB gut microbial community genome (microbiome) when facing that factor and to monitor its diversity. Insects were trapped using specific green Lindgren© traps. A gradient of the captured insect population along the St. Lawrence River was used to create three levels of insects’ density (low, intermediate, and high). After dissection, total DNA extracted from insect guts of each level has been sent for amplicon sequencing of bacterial 16S rRNA gene and fungal ITS2 region. The composition of microbial communities among sample appeared largely diversified with the Simpson index significantly different across the three levels of density for bacteria. Add to that; bacteria were represented by seven phyla and twelve classes, whereas fungi were represented by two phyla and seven known classes. Using principal coordinate analysis (PCoA) based on Bray Curtis distances of 16S rRNA sequences, we observed a significant variation between the structure of the bacterial communities depending on insects’ density. Moreover, the analysis showed significant correlations between some bacterial taxa and the three classes of insects’ density. This study is the first to present a complete overview of the bacterial and fungal communities associated with the gut of EAB base on culture-independent methods, and to correlate those communities with a potential stress factor of the host trees.

Keywords: gut microbiome, DNA, 16S rRNA sequences, emerald ash borer

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Authors: Farideh K. Khosroushahi, Serkan Erdal, Mucip Geni̇şel

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Soil salinity is one of the major abiotic stress factors that restricts arable land and reduces crop productivity worldwide. High salt concentration adversely affects plant growth and development inducing water deficit, ionic toxicity, nutrient imbalance, and lead to oxidative stress. Although the stimulating role of mammalian sex hormones on various biological and biochemical processes under normal and stress condition have been proven, there is no study regarding with these hormone's effect on modulation of the alternative respiration pathway and AOX gene expression. In this study, changes in alternative respiration pathway in leaves of maize seedlings under salinity and the possible modulating effect of estrogen on these changes were investigated. Maize seedlings were grown in a hydroponic media for 11 days and then were exposed to salt stress for 3 days after being sprayed estrogen. The data obtained from oxygen consumption revealed that salt stress elevated cellular respiration value in the leaves. In addition, a marked increase was observed at alternative respiration level in salt-stressed seedlings. Compared to salt application alone, supplementation with estrogen resulted in a significant rise in alternative oxidase (AOX) activities. Similarly, while salt stress caused to rise in expressions of AOX gene compared to control seedlings, estrogen application resulted in further activation of these genes’ expression compared to stressed-seedlings alone. These data revealed that mitigating role of estrogen against the detrimental effects of salt stress is linked to modulation of alternative respiration pathway.

Keywords: alternative oxidase, estrogen, Ssalt stress, AOX, maize

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Authors: Deepak Kumar, Ravi Rajwanshi, Mohd. Aslam Yusuf, Nisha Kant Pandey, Preeti Singh, Mukesh Saxena, Neera Bhalla Sarin

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Global issues are leading to concerns over food security. These include climate change, urbanization, increase in population subsequently leading to greater energy and water demand. Futuristic approach for crop improvement involves gene pyramiding for agronomic traits that empower the plants to withstand multiple stresses. In an earlier study from the laboratory, the efficacy of overexpressing γ-tocopherol methyl transferase (γ-TMT) gene from the vitamin E biosynthetic pathway has been shown to result in six-fold increase of the most biologically active form, the α-tocopherol in Brassica juncea which resulted in alleviation of salt, heavy metal and osmoticum induced stress by the transgenic plants. The glyoxalase I (gly I) gene from the glyoxalase pathway has also been earlier shown by us to impart tolerance against multiple abioitc stresses by detoxification of the cytotoxic compound methylglyoxal in Brassica juncea. Recently, both the transgenes were pyramided in Brassica juncea lines through sexual crosses involving two stable Brassica juncea lines overexpressing γ-TMT and gly I genes respectively. The transgene integration was confirmed by PCR analysis and their mRNA expression was evident by RT-PCR analysis. Preliminary physiological investigations showed ~55% increased seed germination under 200 mM NaCl stress in the pyramided line and 81% higher seed germination under 200 mM mannitol stress as compared to the WT control plants. The pyramided lines also retained more chlorophyll content when the leaf discs were floated on NaCl (200, 400 and 600 mM) or mannitol (200, 400 and 600 mM) compared to the WT control plants. These plants had higher Relative Water Content and greater solute accumulation under stress compared to the parental plants having γ-TMT or the glyI gene respectively. The studies revealed the synergy of two components from different metabolic pathways in enhancing stress hardiness of the transgenic B. juncea plants. It was concluded that pyramiding of genes (γ-TMT and glyI) from diverse pathways can lead to enhanced tolerance to salt and mannitol stress (simulating drought conditions). This strategy can prove useful in enhancing the crop yields under various abiotic stresses.

Keywords: abiotic stress, brassica juncea, glyoxalase I, α-tocopherol

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Authors: Emad Hafez, Mahmoud Seleiman

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Two field experiments were carried out in order to investigate the effect of chemical inducers [benzothiadiazole 0.9 mM L-1, oxalic acid 1.0 mM L-1, salicylic acid 0.2 mM L-1] on physiological and technological traits as well as on yields and antioxidant enzyme activities of barley grown under abiotic stress (i.e. water surplus and deficit conditions). Results showed that relative water content, leaf area, chlorophyll and yield as well as technological properties of barley were improved with chemical inducers application under water surplus and water-stress conditions. Antioxidant enzymes activity (i.e. catalase and peroxidase) were significantly increased in barley grown under water-stress and treated with chemical inducers. Yield and related parameters of barley presented also significant decrease under water-stress treatment, while chemical inducers application enhanced the yield-related traits. Starch and protein contents were higher in plants treated with salicylic acid than in untreated plants when water-stress was applied. In conclusion, results show that chemical inducers application have a positive interaction and synergetic influence and should be suggested to improve plant growth, yield and technological properties of water stressed barley. Salicylic acid application was better than oxalic acid and benzothiadiazole in terms of plant growth and yield improvement.

Keywords: antioxidant enzymes, drought stress, Hordeum vulgare L., quality, yield

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Authors: Abdul Hameed, Muhammad Zaheer Ahmed, Salman Gulzar, Bilquees Gul, Jan Alam, Ahmad K. Hegazy, Abdel Rehman A. Alatar, M. Ajmal Khan

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Seed germination and recovery from salt stress of an annual halophyte Suaeda heterophylla (Kar. and Kir.) Bunge to different iso-osmotic concentrations (0, -0.46, -0.92, -1.38, -1.84, and -2.30 MPa) of NaCl and PEG-6000 at 15/25, 20/30 and 25/35°C in both 12-h temperature and light regimes and in complete darkness were studied. Maximum number of seeds germinated in distilled water and increase in concentrations of both NaCl and PEG-6000 decreased germination at all temperature regimes, light and dark conditions, with higher inhibition in NaCl than PEG-6000. Recovery of germination and viability of seeds were lower in NaCl than PEG-6000 both in the light and dark. Moderate alternate temperatures (20/30°C) and 12-h photoperiod were found to be the optimal for seed germination and recovery. Better seed germination of S. heterophylla when osmotic potential caused both by NaCl and PEG 6000 is lower, temperature regime of 20/30°C and light regime is for 12 h.

Keywords: seed germination, abiotic stresses, Suaeda heterophylla, molecular biology

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Authors: Arash Azarpanah, Masoud Zadehbagheri, Shorangiz Javanmardi

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Abiotic stresses are the principle threat to plant growth and crop productivity all over the world. In order to improve the germination of corn seeds in drought stress conditions, effect of seed priming by various concentrations of salicylic acid (SA) (0.8 and 0.2 mM) on activities of catalase and peroxidase in Zea mays L. plant (Var-Sc.704) was evaluated at Agriculture Research Center located in Arsenjan city in Iran, during summer 2013. A farm research was done in RCBD as factorial with three replications. We considered four irrigation was carried out once the cumulative evaporation from Pan Class A come to 40, 60, 80 and 100 mm. Results illustrated that drought stress significantly increased activities of catalase and peroxidase and also treatment with salicylic acid significantly increased activities of catalase and peroxidase. In addition, treatment with salicylic acid enhances drought tolerance in Zea mays L. plant (Var-Sc.704) with increasing activities of antioxidant enzymes.

Keywords: catalase, corn, salicylic acid, water deficits stress, cumulative evaporation, Pan Class A

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Authors: B. S. Yadav, A. Mani, S. Srivastava

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Chickpea (Cicer arietinum L.) is an annual, self-pollinating, diploid (2n = 2x = 16) pulse crop that ranks second in world legume production after common bean (Phaseolus vulgaris). ICC 4958 flowers approximately 39 days after sowing under peninsular Indian conditions and the crop matures in less than 90 days in rained environments. The estimated collective yield losses due to abiotic stresses (6.4 million t) have been significantly higher than for biotic stresses (4.8 million t). Most legumes are known to be salt sensitive, and therefore, it is becoming increasingly important to produce cultivars tolerant to high-salinity in addition to other abiotic and biotic stresses for sustainable chickpea production. Our aim was to identify the genes that are involved in the defence mechanism against heavy metal toxicity in chickpea and establish the biological network of heavy metal toxicity in chickpea. ICC4958 variety of chick pea was taken and grown in normal condition and 150µM concentration of different heavy metal salt like CdCl₂, K₂Cr2O₇, NaAsO₂. At 15th day leave samples were collected and stored in RNA Later solution microarray was performed for checking out differential gene expression pattern. Our studies revealed that 111 common genes that involved in defense mechanism were up regulated and 41 genes were commonly down regulated during treatment of 150µM concentration of CdCl₂, K₂Cr₂O₇, and NaAsO₂. Biological network study shows that the genes which are differentially expressed are highly connected and having high betweenness and centrality.

Keywords: abiotic stress, biological network, chickpea, microarray

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Authors: Malgorzata Krysiak, Anna Wegrzyn, Maciej Garstka, Radoslaw Mazur

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Under constantly fluctuating environmental conditions, the thylakoid membrane protein network evolved the ability to dynamically respond to changing biotic and abiotic factors. One of the most important protective mechanism is rearrangement of the chlorophyll-protein (CP) complexes, induced by protein phosphorylation. In a temperate climate, low temperature is one of the abiotic stresses that heavily affect plant growth and productivity. The aim of this study was to determine the role of LHCII antenna complex phosphorylation in the dark-chilling response. The study included an experimental model based on dark-chilling at 4 °C of detached chilling sensitive (CS) runner bean (Phaseolus coccineus L.) and chilling tolerant (CT) garden pea (Pisum sativum L.) leaves. This model is well described in the literature as used for the analysis of chilling impact without any additional effects caused by light. We examined changes in thylakoid membrane protein phosphorylation, interactions between phosphorylated LHCII (P-LHCII) and CP complexes, and their impact on the dynamics of photosystem II (PSII) under dark-chilling conditions. Our results showed that the dark-chilling treatment of CS bean leaves induced a substantial increase of phosphorylation of LHCII proteins, as well as changes in CP complexes composition and their interaction with P-LHCII. The PSII photochemical efficiency measurements showed that in bean, PSII is overloaded with light energy, which is not compensated by CP complexes rearrangements. On the contrary, no significant changes in PSII photochemical efficiency, phosphorylation pattern and CP complexes interactions were observed in CT pea. In conclusion, our results indicate that different responses of the LHCII phosphorylation to chilling stress take place in CT and CS plants, and that kinetics of LHCII phosphorylation and interactions of P-LHCII with photosynthetic complexes may be crucial to chilling stress response. Acknowledgments: presented work was financed by the National Science Centre, Poland grant No.: 2016/23/D/NZ3/01276

Keywords: LHCII, phosphorylation, chilling stress, pea, runner bean

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Authors: Abida Kausar, Shagufta Parveen

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The priming of seeds was carried out by two amino acids (phenylalanine and glycine) to improve the drought tolerance potential of two wheat varieties. As wheat is a staple food of more than half of the population of the world, including Pakistan. However, its productivity is mainly adversely affected by abiotic stresses. The current research plan was to investigate the effect of hydropriming and priming by amino acids on wheat varieties under drought stress (50% field capacity). Therefore morphological, biochemical, physiological, and yield attributes were recorded. It was revealed that drought stress significantly decreased the biochemical, morpho-physiological, and growth attributes of the wheat crop. However, the priming treatments have shown a positive correlation with all the studied attributes. It was concluded that priming might involve plant signaling to produce the drought tolerance metabolites under stress conditions which, as a consequence, enhanced the drought tolerance potential of crops.

Keywords: plant biomass, biochemical parameters, chlorophyll contents, yield

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Authors: Elvira Hörandl

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The term “Geographical parthenogenesis” describes the phenomenon that asexual organisms usually occupy larger and more northern distribution areas than their sexual relatives and tend to colonize previously glaciated areas. Several case studies in flowering plants confirm the geographical pattern, but the causal factors behind the phenomenon are still unclear. Previous authors regarded predominant polyploidy in asexual (apomictic) plants as the main factor. However, the geographical pattern is not the rule for sexual polyploids. Recent research confirmed a previous hypothesis of the author that a combination of factors is acting: Although uniparental reproduction provides better colonization abilities, it is most efficient in combination with polyploidy. I will present results on case studies in the genus Ranunculus of both autopolyploid and allopolyploid species and species complexes reproducing via facultative apomixis. Polyploidy seems to contribute mainly to a better tolerance of colder climates and temperate extremes, whereby epigenetic flexibility, changes in gene expression, and phenotypic plasticity play an important role in occupying ecological niches under harsh conditions. Phylogenomic studies entangle complex hybrid origins of asexual taxa, which increases intragenomic heterozygosity of asexual plants. Interestingly, our results suggest an association of sexuality with abiotic stresses, specifically with light stress, which might explain that still, most plants in high altitudes and in southern areas retain sexual reproduction despite other climatic conditions that would favor apomictic plants. We conclude that geographical parthenogenesis results from the complex interplay of the genomic constitution, mode of reproduction and environmental factors.

Keywords: apomixis, polyploidy, hybridization, abiotic stress, epigenetics, phylogenomics

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Authors: Vivian A. Panes, Raymond John S. Rebong, Miel Q. Diaz

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Moringa oleifera Lam. is known mainly for its high nutritional value and medicinal properties contributing to its popular reputation as a 'miracle plant' in the tropical climates where it usually grows. The main objective of this study is to discover the genes and gene products involved in abiotic stress-induced activity that may impact the M. oleifera Lam. mature seeds as well as their corresponding functions. In this study, RNA-sequencing and de novo transcriptome assembly were performed using two assemblers, Trinity and Oases, which produced 177,417 and 120,818 contigs respectively. These transcripts were then subjected to various bioinformatics tools such as Blast2GO, UniProt, KEGG, and COG for gene annotation and the analysis of relevant metabolic pathways. Furthermore, FPKM analysis was performed to identify gene expression levels. The sequences were filtered according to the 'response to stress' GO term since this study dealt with stress response. Clustered Orthologous Groups (COG) showed that the highest frequencies of stress response gene functions were those of cytoskeleton which make up approximately 14% and 23% of stress-related sequences under Trinity and Oases respectively, recombination, repair and replication at 11% and 14% respectively, carbohydrate transport and metabolism at 23% and 9% respectively and defense mechanisms 16% and 12% respectively. KEGG pathway analysis determined the most abundant stress-response genes in the phenylpropanoid biosynthesis at counts of 187 and 166 pathways for Oases and Trinity respectively, purine metabolism at 123 and 230 pathways, and biosynthesis of antibiotics at 105 and 102. Unique and cumulative GO term counts revealed that majority of the stress response genes belonged to the category of cellular response to stress at cumulative counts of 1,487 to 2,187 for Oases and Trinity respectively, defense response at 754 and 1,255, and response to heat at 213 and 208, response to water deprivation at 229 and 228, and oxidative stress at 508 and 488. Lastly, FPKM was used to determine the levels of expression of each stress response gene. The most upregulated gene encodes for thiamine thiazole synthase chloroplastic-like enzyme which plays a significant role in DNA damage tolerance. Data analysis implies that M. oleifera stress response genes are directed towards the effects of climate change more than other stresses indicating the potential of M. oleifera for cultivation in harsh environments because it is resistant to climate change, pathogens, and foreign invaders.

Keywords: stress response, genes, Moringa oleifera, transcriptomics

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Authors: Sabria Barka, Imen Gdara, Zouhour Ouanès, Samia Mouelhi, Monia El Bour, Amel Hamza-Chaffai

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Because dams are large semi-closed reservoirs of pollutants originating from numerous anthropogenic activities, they represent a threat to aquatic life and they should be monitored. The present work aims to use freshwater zooplankton (Copepods and Cladocerans) in order to evaluate the environmental health status of Bir M'cherga dam in Tunisia. Animals were collected in situ monthly between October and August. Genotoxicity (micronucleus test), neurotoxicity (acetylcholinesterase, AChE) and oxidative stress (catalase, CAT and malondialdehyde, MDA) biomarkers were analyzed in zooplankton. High frequencies of micronucleus were observed in zooplankton cells during summer. AChE activities were inhibited during early winter and summer. CAT and MDA biomarker levels showed high seasonal variability, suggesting that animals are permanently exposed to multiple oxidative stress. The results of this study suggest that the Bir Mcherga dam is subject to continuous multi-origin stress, probably amplified by abiotic parameters. It is then recommended to urgently monitor freshwater environments in Tunisia, especially those used for irrigation and consumption.

Keywords: Biomonitoring, Bir Mcherga Dam, cladocerans, copepods, freshwater zooplankton, genotoxicity, neurotoxicity, oxidative stress, Tunisia

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Authors: Rahma Goussi, Walid Derbali, Arafet Manaa, Simone Cantamessa, Graziella Berta, Chedly Abdelly, Roberto Barbato

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Salinity is one of the most important abiotic affecting plant growth and productivity worldwide. Photosynthesis, together with cell growth, is among the primary processes to be affected by salinity. Here, we report the effects of salinity stress on the primary processes of photosynthesis in a model halophyte Thellungiella Salsuginea. Plants were cultivated in hydroponic system with different NaCl concentrations (0, 100, 200 and 400 mM) during 2 weeks. The obtained results showed an obvious change in the photosynthetic efficiency of photosystem I (PSI) and phostosytem II (PSII), related to NaCl concentration supplemented to the medium and the stress duration considered. With moderate salinity (100 and 200 mM NaCl), no significant variation was observed in photosynthetic parameters of PSI and PSII and Chl fluorescence whatever the time of stress application. Also, the photosynthesis apparatus Fo, Fm and Fv fluorescence, as well as Fv/Fm were not affected by salt stress. While a significant decrease was observed on quantum yields Y(I), Y(II) and electron transport rate ETR(I), ETR(II) under high salt treatment (400 mM NaCl) with prolonged period (15 days). This reduction is quantitatively compensated by a corresponding increase of energy dissipation Y(NPQ) and a progressive decrease in Fv/Fm under salt treatment. The intensity of the OJIP fluorescence transient decreased with increase in NaCl concentration, with a major effect observed during prolonged period of salt stress. Ultrastructural analysis with Light Microscopy and Transmission Electron Microscopy of T. salsuginea chloroplasts showed some cellular changes, such as the shape of the mesophyll cells and number of chloroplast/cell only under higher NaCl concentration. Salt-stress caused the swelling of thylakoids in T. Salsuginea mesophyll with more accumulation of starch as compared to control plant.

Keywords: fluorescence, halophyte, photosynthesis, salt stress

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Authors: Osamu Takakuwa, Yuta Mano, Hitoshi Soyama

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This paper reveals the interaction between hydrogen and surface stress in austenitic stainless steel by X-ray diffraction stress measurement and thermal desorption analysis before and after being charged with hydrogen. The surface residual stress was varied by surface finishing using several disc polishing agents. The obtained results show that the residual stress near surface had a significant effect on hydrogen absorption behavior, that is, tensile residual stress promoted the hydrogen absorption and compressive one did opposite. Also, hydrogen induced equi-biaxial stress and this stress has a linear correlation with hydrogen content.

Keywords: hydrogen embrittlement, residual stress, surface finishing, stainless steel

Procedia PDF Downloads 348

Authors: Conor Blunt, Mariluz del Pino-de Elias, Grace Cott, Saoirse Tracy, Rainer Melzer

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The European Green Deal announced in 2021 details agricultural chemical pesticide use and synthetic fertilizer application to be reduced by 50% and 20% by 2030. Increasing and maintaining expected yields under these ambitious goals has strained the agricultural sector. This intergovernmental plan has identified plant biostimulants as one potential input to facilitate this new phase of sustainable agriculture; these products are defined as microorganisms or substances that can stimulate soil and plant functioning to enhance crop nutrient use efficiency, quality and tolerance to abiotic stresses. Spring barley is Ireland’s most widely sown tillage crop, and grain destined for malting commands the most significant market price. Heavy erratic rainfall is forecasted in Ireland’s climate future, and barley is particularly susceptible to waterlogging. Recent findings suggest that plant receptivity to biostimulants may depend on the level of stress inflicted on crops to elicit an assisted plant response. In this study, three biostimulants of different genesis (seaweed, protein hydrolysate and bacteria) are applied to ‘RGT Planet’ malting barley fertilized at three different rates (0 kg/ha, 40 kg/ha, 75 kg/ha) of calcium ammonium nitrogen (27% N) under non-stressed and waterlogged conditions. This 4x3x2 factorial trial design was planted in a completed randomized block with one plant per experimental unit. Leaf gas exchange data and key agronomic and grain quality parameters were analyzed via ANOVA. No penalty on productivity was evident on plants receiving 40 kg/ha of N and bio stimulant compared to 75 kg/ha of N treatments. The main effects of nitrogen application and waterlogging provided the most significant variation in the dataset.

Keywords: biostimulant, Barley, malting, NUE, waterlogging

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