Reactive oxygen species

Drought stress, being the inevitable factor that exists in various environments without recognizing borders and no clear warning thereby hampering plant biomass production, quality, and energy. It is the key important environmental stress that occurs due to temperature dynamics, light intensity, and low rainfall. Despite this, its cumulative, not obvious impact and multidimensional nature severely affects the plant morphological, physiological, biochemical and molecular attributes with adverse impact on photosynthetic capacity. Coping with water scarcity, plants evolve various complex resistance and adaptation mechanisms including physiological and biochemical responses, which differ with species level. The sophisticated adaptation mechanisms and regularity network that improves the water stress tolerance and adaptation in plants are briefly discussed. Growth pattern and structural dynamics, reduction in transpiration loss through altering stomatal conductance and distribution, leaf rolling, root to shoot ratio dynamics, root length increment, accumulation of compatible solutes, enhancement in transpiration efficiency, osmotic and hormonal regulation, and delayed senescence are the strategies that are adopted by plants under water deficit. Approaches for drought stress alleviations are breeding strategies, molecular and genomics perspectives with special emphasis on the omics technology alteration i.e., metabolomics, proteomics, genomics, transcriptomics, glyomics and phenomics that improve the stress tolerance in plants. For drought stress induction, seed priming, growth hormones, osmoprotectants, silicon (Si), selenium (Se) and potassium application are worth using under drought stress conditions in plants. In addition, drought adaptation through microbes, hydrogel, nanoparticles applications and metabolic engineering techniques that regulate the antioxidant enzymes activity for adaptation to drought stress in plants, enhancing plant tolerance through maintenance in cell homeostasis and ameliorates the adverse effects of water stress are of great potential in agriculture.

Drought Stress Impacts on Plants and Different Approaches to Alleviate Its Adverse Effects.

The prokaryotic type II CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-CRISPR-associated 9) system is rapidly revolutionizing the field of genetic engineering, allowing researchers to alter the genomes of a large range of organisms with relative ease. Experimental approaches based on this versatile technology have the potential to transform the field of cancer genetics. Here, we review current approaches for functional studies of cancer genes that are based on CRISPR-Cas, with emphasis on their applicability for the development of next-generation models of human cancer.

Applications of the CRISPR–Cas9 system in cancer biology

Genetic improvement for drought tolerance in chickpea requires a solid understanding of biochemical processes involved with different physiological mechanisms. The objective of this study is to demonstrate genetic variations in altered metabolic levels in chickpea varieties (tolerant and sensitive) grown under contrasting water regimes through ultrahigh-performance liquid chromatography/high-resolution mass spectrometry-based untargeted metabolomic profiling. Chickpea plants were exposed to drought stress at the 3-leaf stage for 25 days, and the leaves were harvested at 14 and 25 days after the imposition of drought stress. Stress produced significant reduction in chlorophyll content, Fv /Fm , relative water content, and shoot and root dry weight. Twenty known metabolites were identified as most important by 2 different methods including significant analysis of metabolites and partial least squares discriminant analysis. The most pronounced increase in accumulation due to drought stress was demonstrated for allantoin, l-proline, l-arginine, l-histidine, l-isoleucine, and tryptophan. Metabolites that showed a decreased level of accumulation under drought conditions were choline, phenylalanine, gamma-aminobutyric acid, alanine, phenylalanine, tyrosine, glucosamine, guanine, and aspartic acid. Aminoacyl-tRNA and plant secondary metabolite biosynthesis and amino acid metabolism or synthesis pathways were involved in producing genetic variation under drought conditions. Metabolic changes in light of drought conditions highlighted pools of metabolites that affect the metabolic and physiological adjustment in chickpea that reduced drought impacts.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/pce.13195

UPLC-HRMS-based untargeted metabolic profiling reveals changes in chickpea (Cicer arietinum) metabolome following long-term drought stress.

Climate change is causing soil salinization, resulting in crop losses throughout the world The ability of plants to tolerate salt stress is determined by multiple biochemical and molecular pathways Here we discuss physiological, biochemical, and cellular modulations in plants in response to salt stress Knowledge of these modulations can assist in assessing salt tolerance potential and the mechanisms underlying salinity tolerance in plants Salinity-induced cellular damage is highly correlated with generation of reactive oxygen species, ionic imbalance, osmotic damage, and reduced relative water content Accelerated antioxidant activities and osmotic adjustment by the formation of organic and inorganic osmolytes are significant and effective salinity tolerance mechanisms for crop plants In addition, polyamines improve salt tolerance by regulating various physiological mechanisms, including rhizogenesis, somatic embryogenesis, maintenance of cell pH, and ionic homeostasis This research project focuses on three strategies to augment salinity tolerance capacity in agricultural crops: salinity-induced alterations in signaling pathways; signaling of phytohormones, ion channels, and biosensors; and expression of ion transporter genes in crop plants (especially in comparison to halophytes)

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Insights into the Physiological and Biochemical Impacts of Salt Stress on Plant Growth and Development

Phytohormones are endogenously produced organic substances indispensable for regulating plant growth and yield and also play major role in inducing tolerance to plants against various biotic and abiotic stresses. The convergence points among hormone signal transduction cascades are considered as cross-talk which are crucial for plant development as well as for plant responses to biotic and abiotic stresses. Hormones interact by activating either a second messenger or through a phosphorylation cascade. These transduction cascades lead to the regulation of gene expression that directly affects the biosynthesis or action of different hormones and developmental processes in coordination with multiple stimuli. Hormone synthesis, signal transduction, perception and cross-talk create a complex network. Interaction of plant growth promoting rhizobacteria (PGPR) which form intimate association with the roots of higher plants also modulate the level of endogenous phytohormones and demonstrate a new paradigm for hormonal interaction. The ratio of hormones changes with ontogeny of plant and the specific ratio of growth promoting and growth inhibiting hormones determine the response of plants. Furthermore, the sensitivity of plant tissue to each hormone changes with the exposure to stresses. This review is a compilation of the interactions between phytohormones and plant development. The cross talk between different hormones under abiotic and biotic stresses will be enumerated. Hormone and stress-responsive cis elements and the trans-regulation capabilities of miRNAs for the coordination of multiple hormonal responses will be discussed. Finally the role of PGPR will be evaluated under various environmental stresses with particular emphasis on phytohormone production and its interaction with host plant physiology. PGPR provides cross protective properties through improvement in defense mechanism controlling pathogen resistance through induced systemic resistance (ISR) and alleviating abiotic stress through influencing the phytohormones metabolism. PGPR isolates from stressed soil/stressed host plants impart tolerance to plants against abiotic and biotic stresses by modulating the production of phytohormones and alteration in their sensitivity to respond. Bacteria communicate with each other through quorum sensing molecules which also regulate gene expression and phytohormone production. The intricate relationship between other microbes/fungi and their residual effects on plant rhizosphere phytohormones need further investigation for better understanding of bacterial coordination with plants.

Crosstalk amongst phytohormones from planta and PGPR under biotic and abiotic stresses

The present study was aimed to isolate and characterize plant growth promoting rhizobacteria (PGPR) from the rhizosphere of rainfed area (Karak) in Pakistan. The influence of isolated rhizobacteria, in association with salicylic acid (SA), physiological attributes, drought tolerance potential, and phytoremediation in drought-stressed sunflower exposed was investigated. The isolated bacteria were named P1 and P2 and characterized on the basis of colony morphology and biochemical traits. Both PGPR P1 and P2 were identified on the basis of 16S-rRNA gene sequencing as Planomicrobium chinense strain P1 (Accession No. MF616408) and Bacillus cereus strain P2 (Accession No. MF616406). The fresh cultures (24 h old) of isolates were used to soak the seeds pre-sowing. SA was foliar applied at three-leaf-stage. Likewise, the 30-days-old seedlings (three leaf stage) were exposed to drought stress. Drought stress was imposed to 30-days-old plants (three-leaf stage) by withholding water supply for the next 15 days until the soil water content reached 10%. The PGPR and/or SA treatment resulted in significant accumulation of Cd (84%), Pb (66%), and Ni (65%) in the rhizosphere. PGPR also induced accumulation of Cd and Ni in plant shoot. Combined treatment of PGPR and SA increased the Cu (21%), Co (11%), and Zn (8%) accumulation but decreased (12%) the Fe accumulation as compared to coinoculation of PGPR P1 and P2. Inoculation of plants with PGPR significantly increased shoot length (60%), root length (68%), root fresh (61%), and dry (63%) biomass under water stress. The inoculated plants had increased chlorophyll (67%), carotenoid (70%), leaf protein (64%), sugar (64%), and phenolic (62%) contents while lower leaf proline (62%) content, malondialdehyde (MDA) (64%), and antioxidant enzymes (67%) which suggest their role in drought tolerance. It is concluded that integrative use of PGPR in combination with SA found to be an efficacious strategy to improve the phytoremediation of heavy metals and plant growth under stressed conditions particularly under water-deficient conditions.

Impact of Salicylic Acid and PGPR on the Drought Tolerance and Phytoremediation Potential of Helianthus annus

Nanotechnology has shown promising potential tools and strategies at the nanometer scale to improve food production and meet the future demands of agricultural and food security. However, considering nanotechnology’s potential benefits to date, their applicability has not yet reached up to field conditions. Increasing concerns regarding absorption, translocation, bioavailability, toxicity of nanoparticles, and impropriety of the regulatory framework restrict the complete acceptance and inclination of the agricultural sector to implement nanotechnologies. The biological function of nanoparticles depends on their physicochemical properties, the method of application, and concentration. The effects of the various types of nanoparticles (NPs) on plants were determined to increase seed germination and biomass or grain yield. The NPs also increased the plant’s resistance to various biotic and abiotic stresses. The plant’s biological functions depend on the events that occur at the molecular level. However, little progress has been made at the molecular level influenced by nanoparticles, which is an important step in evaluating potential mechanisms and plants’ effects. Therefore, it is important to understand plants’ underlying mechanism and response towards nanoparticles, and the gene expression changes through molecular approaches. The associations of nanomaterials with plant cells, the process of internalization, and the distribution of biomolecules using nanoparticles as a carrier are studied but not well understood. The transmission of biomolecules, such as nucleic acids, is a major obstacle due to cell walls, limiting the application of nanomaterials in crop enhancement mediated by genetic engineering. Recently, the use of different nanomaterials for nucleic acid delivery in plant cells has been published. Here, we aim to update researchers on the absorption and translocation of nanoparticles and elaborate on the importance of nanoparticles in agriculture and crop stress tolerance.

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Uptake, Translocation, and Consequences of Nanomaterials on Plant Growth and Stress Adaptation

Abiotic stresses, such as drought, salinity, heavy metals, variations in temperature, and ultraviolet (UV) radiation, are antagonistic to plant growth and development, resulting in an overall decrease in plant yield. These stresses have direct effects on the rhizosphere, thus severely affect the root growth, and thereby affecting the overall plant growth, health, and productivity. However, the growth-promoting rhizobacteria that colonize the rhizosphere/endorhizosphere protect the roots from the adverse effects of abiotic stress and facilitate plant growth by various direct and indirect mechanisms. In the rhizosphere, plants are constantly interacting with thousands of these microorganisms, yet it is not very clear when and how these complex root, rhizosphere, and rhizobacteria interactions occur under abiotic stresses. Therefore, the present review attempts to focus on root-rhizosphere and rhizobacterial interactions under stresses, how roots respond to these interactions, and the role of rhizobacteria under these stresses. Further, the review focuses on the underlying mechanisms employed by rhizobacteria for improving root architecture and plant tolerance to abiotic stresses.

Insights into the Interactions among Roots, Rhizosphere, and Rhizobacteria for Improving Plant Growth and Tolerance to Abiotic Stresses: A Review.

Heat and drought stresses are presently the principal risk on world's food quantity, limiting yield. Both of these two stresses affect plants metabolism, physiological and morphological processes, which ultimately reduces the productivity. The plant cell develops different stress induced self-defence mechanisms to reduce the effect of stresses. These defence mechanisms are developed by modifying gene expression pattern, which results in qualitative and quantitative deviations in proteins synthesis, leading to the modulation of certain metabolic and defensive pathways. New metabolic profiling technologies offer a great opportunity for biologist to understand defence mechanism of plants under stress conditions. Metabolomics technologies presently enabled the using of different multi-variate analyses, generated from various hyphenated and chromatographic discovery systems, such as gas or liquid chromatography together with mass spectrometry, or nuclear magnetic resonance (NMR) based methods. Investigation and mining of metabolomics data can be done through a blend of different statistical methods, such as independent component analysis and analysis of variance. Metabolomics in combination with gene expression, protein interaction and other different regulatory pathways can be useful to diverse organisms with trivial alterations. In recent time, this technology has been used to investigate drought tolerance in plant crops to find particular stress related patterns in metabolic expression. These studies identified the vital roles of primary and secondary metabolites associated with abiotic stress tolerance.

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Shahid Ali

Papers

Crosstalk amongst phytohormones from planta and PGPR under biotic and abiotic stresses

Impact of Salicylic Acid and PGPR on the Drought Tolerance and Phytoremediation Potential of Helianthus annus

Uptake, Translocation, and Consequences of Nanomaterials on Plant Growth and Stress Adaptation

Insights into the Interactions among Roots, Rhizosphere, and Rhizobacteria for Improving Plant Growth and Tolerance to Abiotic Stresses: A Review.

Advances in detection of stress tolerance in plants through metabolomics approaches