Abiotic Stress in Crop Species: Improving Tolerance by Applying Plant Metabolites

Effect of seed priming with auxin on ROS detoxification and carbohydrate metabolism and their relationship with germination and early seedling establishment in salt stressed maize

As crucial stages in the plant ontogeny, germination and seedling establishment under adverse conditions greatly determine staple crop growth and productivity. In the context of green technologies aiming to improve crop yield, seed priming is emerging as an effective approach to enhance seed vigor and germination performance under salt stress. In this study, we assess the efficiency of seed priming with indole-3-acetic acid (IAA) in mitigating the adverse effects of salt stress on maize (Zea mays L.) seedlings during germination and early seedling stages. In unprimed seeds, salt stress reduced germination indices, and seedling (both radicle and coleoptile) growth, together with decreased tissue hydration. However, seed priming using IAA significantly improved maize salt response, as reflected by the increased seed germination dynamics, early seedling establishment, and water status. Besides, seedlings from IAA-primed seeds showed a higher activity of α-amylase, resulting in increased sugar contents in roots and coleoptiles of salt-stressed plants. Further, IAA-seed priming stimulated the accumulation of endogenous IAA in salt-stressed seedlings, in concomitance with a significant effect on reactive oxygen species detoxification and lipid peroxidation prevention. Indeed, our data revealed increased antioxidant enzyme activities, differentially regulated in roots and coleoptiles, leading to increased activities of the antioxidant enzymes (SOD, CAT and GPX). In summary, data gained from this study further highlight the potential of IAA in modulating early interactions between multiple signaling pathways in the seed, endowing maize seedlings with enhanced potential and sustained tolerance to subsequent salt stress.

Enhancing high-efficient cadmium biosorption of Escherichia coli via cell surface displaying metallothionien CUP1

Cadmium (Cd) is one of the common heavy metal pollutants in soil, which can induce various diseases and pose a serious threat to human health. Metallothioneins (MTs) are well-known for their excellent metal binding ability due to a high content of cysteine, which has great potential for heavy metal chelation. In this study, we used the Escherichia coli (E. coli) surface display system LPP-OmpA to construct a recombinant plasmid pBSD-LCF encoding LPP-OmpA-CUP1-Flag fusion protein. Then we displayed the metallothionein CUP1 from Saccharomyces cerevisiae on E. coli DH5α surface for Cd removing. The feasibility of surface display of metallothionein CUP1 in recombinant E. coli DH5α (pBSD-LCF) by Lpp-OmpA system was proved by flow cytometry and western blot analysis, and the specificity of the fusion protein in the recombinant strain was also verified. The results showed that the Cd2+ resistance capacity of DH5α (pBSD-LCF) was highly enhanced by about 200%. Fourier-transform infrared spectroscopy showed that sulfhydryl and sulfonyl groups were involved in Cd2+ binding to cell surface of DH5α (pBSD-LCF). Meanwhile, Cd removal rate by DH5α (pBSD-LCF) was promoted to 95.2%. Thus, the recombinant strain E. coli DH5α (pBSD-LCF) can effectively chelate environmental metals, and the cell surface expression of metallothionein on E. coli can provide new ideas and directions for heavy metals remediation.

Integrated Transcriptomic and Proteomic Analysis Reveals Molecular Mechanisms of the Cold Stress Response during the Overwintering Period in Blueberries (Vaccinium spp.)

In China, the Liaodong Peninsula is an important growing area for blueberries because of the high organic matter content in the soil, the abundance of light, and the large temperature difference between day and night. However, the low temperature and relative humidity of the air during the winter and early spring in the Liaodong Peninsula are the main reasons for the damage to blueberry plants. Here, we documented the transcriptome and proteome dynamics in response to cold stress in three blueberry cultivars ('Northland', 'Bluecrop', and 'Berkeley'). Functional enrichment analysis indicated that many differentially expressed genes (DEGs) and differentially abundant proteins (DAPs) were mainly involved in the pathways of protein processing in the endoplasmic reticulum, the glutathione metabolism pathway, and ribosomes. We identified 12,747 transcription factors (TFs) distributed in 20 families. Based on our findings, we speculated that cold tolerance development was caused by the expression of calcium-related genes (CDPKs and CMLs), glutathione proteins, and TFs (NAC, WRKY, and ERF). Our investigation found that three cultivars experienced cold damage when exposed to temperatures between -9 °C and -15 °C in the field. Therefore, the cold resistance of blueberries during overwintering should not only resist the influence of low temperatures but also complex environmental factors such as strong winds and low relative humidity in the air. The order of cold resistance strength in the three blueberry cultivars was 'Berkeley', 'Bluecrop', and 'Northland'. These results provide a comprehensive profile of the response to cold stress, which has the potential to be used as a selection marker for programs to improve cold tolerance in blueberries.

Nanoparticles and root traits: mineral nutrition, stress tolerance and interaction with rhizosphere microbiota

MAIN CONCLUSION

This review article highlights a broader perspective of NPs and plant-root interaction by focusing on their beneficial and deleterious impacts on root system architecture (RSA). The root performs a vital function by securing itself in the soil, absorbing and transporting water and nutrients to facilitate plant growth and productivity. In dicots, the architecture of the root system (RSA) is markedly shaped by the development of the primary root and its branches, showcasing considerable adaptability in response to changes in the environment. For promoting agriculture and combating global food hunger, the use of nanoparticles (NPs) may be an exciting option, for which it is essential to understand the behaviour of plants under NPs exposure. The nature of NPs and their physicochemical characteristics play a significant role in the positive/negative response of roots and shoots. Root morphological features, such as root length, root mass and root development features, may regulated positively/negatively by different types of NPs. In addition, application of NPs may also enhance nutrient transport and soil fertility by the promotion of soil microorganisms including plant growth-promoting rhizobacteria (PGPRs) and also soil enzymes. Interestingly the interaction of nanomaterials (NMs) with rhizospheric bacteria can enhance plant development and soil health. However, some studies also suggested that the increased use of several types of engineered nanoparticles (ENPs) may disrupt the equilibrium of the soil-root interface and unsafe morphogenesis by causing the browning of roots and suppressing the growth of root and soil microbes. Thus, this review article has sought to compile a broader perspective of NPs and plant-root interaction by focusing on their beneficial or deleterious impacts on RSA.

Melatonin Interaction with Other Phytohormones in the Regulation of Abiotic Stresses in Horticultural Plants

Horticultural crops play a vital role in global food production, nutrition, and the economy. Horticultural crops are highly vulnerable to abiotic stresses. These abiotic stresses hinder plant growth and development by affecting seed germination, impairing photosynthetic activity, and damaging root development, thus leading to a decrease in fruit yield, quality, and productivity. Scientists have conducted extensive research to investigate the mechanisms of resilience and the ability to cope with environmental stresses. In contrast, the use of phytohormones to alleviate the detrimental impacts of abiotic stresses on horticulture plants has been generally recognized as an effective method. Among phytohormones, melatonin (MT) is a novel plant hormone that regulates various plants' physiological functions such as seedling development, root system architecture, photosynthetic efficiency, balanced redox homeostasis, secondary metabolites production, accumulation of mineral nutrient uptake, and activated antioxidant defense system. Importantly, MT application significantly restricted heavy metals (HMs) uptake and increased mineral nutrient accumulation by modifying the root architecture system. In addition, MT is a naturally occurring, multifunctional, nontoxic biomolecule having antioxidant properties. Furthermore, this review described the hormonal interaction between MT and other signaling molecules in order to enhance abiotic stress tolerance in horticulture crops. This review focuses on current research advancements and prospective approaches for enhancing crop tolerance to abiotic stress.

Silicon: A valuable soil element for improving plant growth and CO2 sequestration

BACKGROUND

Silicon (Si), the second most abundant and quasi-essential soil element, is locked as a recalcitrant silicate mineral in the Earth's crust. The physical abundance of silicates can play an essential role in increasing plant productivity. Plants store Si as biogenic silica (phytoliths), which is mobilized through a chemical weathering process in the soil.

AIM OF REVIEW

Although Si is a critical element for plant growth, there is still a considerable need to understand its dissolution, uptake, and translocation in agroecosystems. Here, we show recent progress in understanding the interactome of Si, CO2, the microbiome, and soil chemistry, which can sustainably govern silicate dissolution and cycling in agriculture.

KEY SCIENTIFIC CONCEPTS OF THIS REVIEW

Si cycling is directly related to carbon cycling, and the resulting climate stability can be enhanced by negative feedback between atmospheric CO2 and the silicate uptake process. Improved Si mobilization in the rhizosphere by the presence of reactive elements (for example, Ca, Na, Al, Zn, and Fe) and Si uptake through genetic transporters in plants are crucial to achieving the dual objectives of (i) enhancing crop productivity and (ii) abiotic stress tolerance. Furthermore, the microbiome is a symbiotic partner of plants. Bacterial and fungal microbiomes can solubilize silicate minerals through intriguingly complex bioweathering mechanisms by producing beneficial metabolites and enzymes. However, the interaction of Si with CO2 and the microbiome's function in mobilization have been understudied. This review shows that enhancing our understanding of Si, CO2, the microbiome, and soil chemistry can help in sustainable crop production during climatic stress events.

Surviving a Double-Edged Sword: Response of Horticultural Crops to Multiple Abiotic Stressors

Climate change-induced weather events, such as extreme temperatures, prolonged drought spells, or flooding, pose an enormous risk to crop productivity. Studies on the implications of multiple stresses may vary from those on a single stress. Usually, these stresses coincide, amplifying the extent of collateral damage and contributing to significant financial losses. The breadth of investigations focusing on the response of horticultural crops to a single abiotic stress is immense. However, the tolerance mechanisms of horticultural crops to multiple abiotic stresses remain poorly understood. In this review, we described the most prevalent types of abiotic stresses that occur simultaneously and discussed them in in-depth detail regarding the physiological and molecular responses of horticultural crops. In particular, we discussed the transcriptional, posttranscriptional, and metabolic responses of horticultural crops to multiple abiotic stresses. Strategies to breed multi-stress-resilient lines have been presented. Our manuscript presents an interesting amount of proposed knowledge that could be valuable in generating resilient genotypes for multiple stressors.

Effect of Elicitor Treatments on Quality Attributes in Blueberry: Implications of Cultivar and Environmental Conditions

Elicitors of plant defence responses can trigger defence mechanisms that are able to protect plant tissues from biotic or abiotic stresses. Since one defence response involves the activation of secondary metabolites' biosynthesis, the purpose of this study was to evaluate the effect of chitosan and melatonin pre-harvest treatments on the quality and the nutritional parameters of the fruits of blueberry (Vaccinium corymbosum L.). Across the two years of experiment, three different cultivars (cv.s. 'Cosmopolitan', 'Hortblue Poppins' and 'Legacy') were treated with 1% chitosan or 100 µM melatonin every two weeks during the ripening season and ripe fruits were progressively harvested and analysed. The treatment with both elicitors had only slight effects on dry matter, soluble solids content, titratable acidity and pH, with a cultivar-dependent response. On the other hand, elicitors significantly affected the levels of phenylpropanoid and antioxidant compounds in all cvs. in both years, with a higher accumulation of total anthocyanins and phenolics and the enhancement of the antioxidant capacity, with positive effects on the nutraceutical quality of fruits. The anthocyanin profile in terms of both absolute concentrations and the relative proportion of single anthocyanins was affected by both harvest year and cv., highlighting the role of the genetic background in the plant response to environmental conditions (with particular reference to summer heat stress) and to elicitor treatments.

Examination of Primary and Secondary Metabolites Associated with a Plant-Based Diet and Their Impact on Human Health

The consumption of plant-based diets has become a burgeoning trend, and they are increasingly consumed globally owing to their substantial energy intensity and dietetic advantages. Plants possess numerous bioactive components that have been recognized to exhibit manifold health-promoting assets. Comprehension of the synthesis of these primary and secondary metabolites by plants and their method of action against several chronic illnesses is a significant requirement for understanding their benefits to human health and disease prevention. Furthermore, the association of biologically active complexes with plants, humans, disease, medicine, and the underlying mechanisms is unexplored. Therefore, this review portrays various bioactive components derived from plant sources associated with health-promoting traits and their action mechanisms. This review paper predominantly assembles proposed plant-derived bioactive compounds, postulating valuable evidence aimed at perceiving forthcoming approaches, including the selection of potent bioactive components for formulating functional diets that are effective against several human disorders. This meticulous evidence could perhaps provide the basis for the advanced preemptive and therapeutic potential promoting human health. Hence, delivery opens possibilities for purchasers to approach the lucrative practice of plants as a remedy, produce novel products, and access new marketplaces.

Phytohormones-mediated strategies for mitigation of heavy metals toxicity in plants focused on sustainable production

KEY MESSAGE

In this manuscript, authors reviewed and explore the information on beneficial role of phytohormones to mitigate adverse effects of heavy metals toxicity in plants. Global farming systems are seriously threatened by heavy metals (HMs) toxicity, which can result in decreased crop yields, impaired food safety, and negative environmental effects. A rise in curiosity has been shown recently in creating sustainable methods to reduce HMs toxicity in plants and improve agricultural productivity. To accomplish this, phytohormones, which play a crucial role in controlling plant development and adaptations to stress, have emerged as intriguing possibilities. With a particular focus on environmentally friendly farming methods, the current review provides an overview of phytohormone-mediated strategies for reducing HMs toxicity in plants. Several physiological and biochemical activities, including metal uptake, translocation, detoxification, and stress tolerance, are mediated by phytohormones, such as melatonin, auxin, gibberellin, cytokinin, ethylene, abscisic acid, salicylic acid, and jasmonates. The current review offers thorough explanations of the ways in which phytohormones respond to HMs to help plants detoxify and strengthen their resilience to metal stress. It is crucial to explore the potential uses of phytohormones as long-term solutions for reducing the harmful effects of HMs in plants. These include accelerating phytoextraction, decreasing metal redistribution to edible plant portions, increasing plant tolerance to HMs by hormonal manipulation, and boosting metal sequestration in roots. These methods seek to increase plant resistance to HMs stress while supporting environmentally friendly agricultural output. In conclusion, phytohormones present potential ways to reduce the toxicity of HMs in plants, thus promoting sustainable agriculture.

Microbiome structure variation and soybean's defense responses during flooding stress and elevated CO2

Introduction

With current trends in global climate change, both flooding episodes and higher levels of CO2 have been key factors to impact plant growth and stress tolerance. Very little is known about how both factors can influence the microbiome diversity and function, especially in tolerant soybean cultivars. This work aims to (i) elucidate the impact of flooding stress and increased levels of CO2 on the plant defenses and (ii) understand the microbiome diversity during flooding stress and elevated CO2 (eCO2).

Methods

We used next-generation sequencing and bioinformatic methods to show the impact of natural flooding and eCO2 on the microbiome architecture of soybean plants' below- (soil) and above-ground organs (root and shoot). We used high throughput rhizospheric extra-cellular enzymes and molecular analysis of plant defense-related genes to understand microbial diversity in plant responses during eCO2 and flooding.

Results

Results revealed that bacterial and fungal diversity was substantially higher in combined flooding and eCO2 treatments than in non-flooding control. Microbial diversity was soil>root>shoot in response to flooding and eCO2. We found that sole treatment of eCO2 and flooding had significant abundances of Chitinophaga, Clostridium, and Bacillus. Whereas the combination of flooding and eCO2 conditions showed a significant abundance of Trichoderma and Gibberella. Rhizospheric extra-cellular enzyme activities were significantly higher in eCO2 than flooding or its combination with eCO2. Plant defense responses were significantly regulated by the oxidative stress enzyme activities and gene expression of Elongation factor 1 and Alcohol dehydrogenase 2 in floodings and eCO2 treatments in soybean plant root or shoot parts.

Conclusion

This work suggests that climatic-induced changes in eCO2 and submergence can reshape microbiome structure and host defenses, essential in plant breeding and developing stress-tolerant crops. This work can help in identifying core-microbiome species that are unique to flooding stress environments and increasing eCO2.

Nitric oxide reduces cadmium uptake in wheat (Triticum aestivum L.) by modulating growth, mineral uptake, yield attributes, and antioxidant profile

Wheat (Triticum aestivum L.) is among the plants that are at risk from cadmium (Cd), a hazardous heavy metal that can be fatal due to its rapid absorption and high mobility. Being taken up from the soil and moving to the shoots and roots of edible plants, it enters the food chain and poses a health concern to people worldwide. A strategically important cereal crop, wheat has a demonstrated role in human health systems, particularly in poor nations. In this study, we describe the effects of nitric oxide (NO) on the growth, nutrition, and physiological functions of commercially cultivated wheat cvs. Galaxy 2013 and Akbar 2019 under Cd stress. Four-week-old plants were subjected to Cd (0.5 mM) stress, and after 2 weeks of Cd toxicity, foliar application of nitric oxide (100 and 150 μM) was carried out. As evident from excessive antioxidant production, Cd toxicity increased reactive oxygen species (ROS) level like H2O2 and significantly (p ≤ 0.001) decreased nutrient acquisition, growth, and yield attributes of plants under experiment. The severity of the effect varied between cultivars under investigation. A minimum accumulation of MDA (44%) and H2O2 (55%) was found in the cv. Akbar 2019 under Cd stress, whilst cv. Galaxy 2013 showed the highest accumulation of the oxidative stress indicators malondialdehyde content (MDA) (48%) and H2O2 (60%). Reduced and oxidized glutathione contents were also increased under Cd-induced toxicity. The application of NO resulted in a significant improvement of 22, 25, 25, and 30% in shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight, respectively. Additionally, there was an increased uptake of Ca+2 (16%), K+1 (5%), chlorophyll a (46%), b (32%), a/b ratio (41%), and carotenoid (28%). When compared with Cd-stressed plants, yield parameters like 100 grain weight, number of tillers plant-1, and grain yield plant-1 improved by 14, 17, and 33%, respectively, under NO application. We concluded from the results of this study that NO treatments increased plant development by lowering oxidative stress and limiting Cd uptake. It is inferred from the results of this study that wheat production with reduced heavy metal uptake may be facilitated using NO due to its cytoprotective properties and its interaction with ROS.

Identification of Stress-Responsive Metabolites in Plants Using an Untargeted Metabolomics Approach

Stress can affect different groups of plant metabolites and multiple signaling pathways. Untargeted metabolomics enables the collection of whole-spectrum data for the entire metabolite content present in plant tissues at that point in time. We present a thorough approach for large-scale, untargeted metabolomics of plant tissues using reverse-phase liquid chromatography connected to high-resolution mass spectrometry (LC-MS) of dilute methanolic extract. MZmine is a specialized computer software that automates the alignment and baseline modification of all derived mass peaks across all samples, resulting in precise information on the relative abundance of hundreds of metabolites reflected by thousands of mass signals. Further processing with statistic and bioinformatic techniques will provide a comprehensive perspective of the variations and connections among groups of samples.

Abiotic Stress Tolerance in Crop and Medicinal Plants

Climate change and the increased need for crop production highlight the urgent importance of introducing crops with increased tolerance to adverse environmental conditions [...].

Evaluation of potassium-enriched biochar and GA3 effectiveness for Improving wheat growth under drought stress

Osmotic stress is a significant concern in agricultural crop production as it can harm crop growth, development, and productivity. Agriculture crops are particularly vulnerable to osmotic stress due to their reliance on water availability for various physiological processes. Organic amendments like activated carbon biochar and growth hormone gibberellic acid (GA3) can play a vital role. However, the time needed is to modify the established amendment to achieve better results. That's why the current study used potassium-enriched biochar (KBC = 0.75%) with and without GA3 (15 mg/L) as amendments under no osmotic stress and osmotic stress in wheat. Results showed that GA3 + KBC caused significant enhancement in germination (9.44%), shoot length (29.30%), root length (21.85%), shoot fresh weight (13.56%), shoot dry weight (68.38), root fresh weight (32.68%) and root dry weight (28.79%) of wheat over control under osmotic stress (OS). A significant enhancement in chlorophyll a, chlorophyll b and total chlorophyll, while the decline in electrolyte leakage of wheat, also validated the effectiveness of GA3 + KBC over control in OS. In conclusion, GA3 + KBC is the most effective among all applied treatments for improving wheat growth attributes under no osmotic and osmotic stress. Further research is needed at the field level, focusing on various cereal crops, to establish GA3 + KBC as the optimal treatment for effectively mitigating the impacts of osmotic stress.

Foliar Application of Sulfur-Containing Compounds-Pros and Cons

Sulfate is taken up from the soil solution by the root system; and inside the plant, it is assimilated to hydrogen sulfide, which in turn is converted to cysteine. Sulfate is also taken up by the leaves, when foliage is sprayed with solutions containing sulfate fertilizers. Moreover, several other sulfur (S)-containing compounds are provided through foliar application, including the S metabolites hydrogen sulfide, glutathione, cysteine, methionine, S-methylmethionine, and lipoic acid. However, S compounds that are not metabolites, such as thiourea and lignosulfonates, along with dimethyl sulfoxide and S-containing adjuvants, are provided by foliar application-these are the S-containing agrochemicals. In this review, we elaborate on the fate of these compounds after spraying foliage and on the rationale and the efficiency of such foliar applications. The foliar application of S-compounds in various combinations is an emerging area of agricultural usefulness. In the agricultural practice, the S-containing compounds are not applied alone in spray solutions and the need for proper combinations is of prime importance.

Anthocyanin in blood oranges: a review on postharvest approaches for its enhancement and preservation

Anthocyanin concentration is considered an important fruit quality index of blood oranges and has gained popularity among consumers due to its antioxidant capacity, therapeutic properties, and prevention of some human diseases. Anthocyanin biosynthesis occurs in the cytoplasmic face of the endoplasmic reticulum by multi-enzymes complexes through the flavonoid pathway. Polyphenoloxidase (PPO) and β-glucosidase (anthocyanase) are the enzymes responsible for anthocyanin degradation. Blood oranges are cold-dependent for anthocyanin biosynthesis and accumulation, and thus, the low temperature of storage can enhance anthocyanin concentration and improve internal fruit quality. In addition, anthocyanin accumulation can be accelerated by postharvest technologies, either physical treatments or chemical elicitors. However, low temperatures can induce chilling injury (CI) incidence in blood oranges. Postharvest chemical elicitors treatments can enhance anthocyanin accumulation and prevent CI. This review provides the most updated information about postharvest tools modulating the anthocyanin content, and the role of enhancing and preserving pigmentation to produce blood orange with the highest quality standards.

Effect of ethylene pretreatment on tomato plant responses to salt, drought, and waterlogging stress

Salinity, drought, and waterlogging are common environmental stresses that negatively impact plant growth, development, and productivity. One of the responses to abiotic stresses is the production of the phytohormone ethylene, which induces different coping mechanisms that help plants resist or tolerate stress. In this study, we investigated if an ethylene pretreatment can aid plants in activating stress-coping responses prior to the onset of salt, drought, and waterlogging stress. Therefore, we measured real-time transpiration and CO2 assimilation rates and the impact on biomass during and after 3 days of abiotic stress. Our results showed that an ethylene pretreatment of 1 ppm for 4 h did not significantly influence the negative effects of waterlogging stress, while plants were more sensitive to salt stress as reflected by enhanced water losses due to a higher transpiration rate. However, when exposed to drought stress, an ethylene pretreatment resulted in reduced transpiration rates, reducing water loss during drought stress. Overall, our findings indicate that pretreating tomato plants with ethylene can potentially regulate their responses during the forthcoming stress period, but optimization of the ethylene pre-treatment duration, timing, and dose is needed. Furthermore, it remains tested if the effect is related to the stress duration and severity and whether an ethylene pretreatment has a net positive or negative effect on plant vigor during stress recovery. Further investigations are needed to elucidate the mode of action of how ethylene priming impacts subsequent stress responses.

Apple CRISPR-Cas9-A Recipe for Successful Targeting of AGAMOUS-like Genes in Domestic Apple

Fruit trees and other fruiting hardwood perennials are economically valuable, and there is interest in developing improved varieties. Both conventional breeding and biotechnology approaches are being utilized towards the goal of developing advanced cultivars. Increased knowledge of the effectiveness and efficiency of biotechnology approaches can help guide use of the CRISPR gene-editing technology. Here, we examined CRISPR-Cas9-directed genome editing in the valuable commodity fruit tree Malus x domestica (domestic apple). We transformed two cultivars with dual CRISPR-Cas9 constructs designed to target two AGAMOUS-like genes simultaneously. The main goal was to determine the effectiveness of this approach for achieving target gene changes. We obtained 6 Cas9 control and 38 independent CRISPR-Cas9 events. Of the 38 CRISPR-Cas9 events, 34 (89%) had gene edits and 14 (37%) showed changes to all alleles of both target genes. The most common change was large deletions, which were present in 59% of all changed alleles, followed by small deletions (21%), small insertions (12%), and a combination of small insertions and deletions (8%). Overall, a high rate of successful gene alterations was found. Many of these changes are predicted to cause frameshifts and alterations to the predicted peptides. Future work will include monitoring the floral development and floral form.

Microbial-Derived γ-Aminobutyric Acid: Synthesis, Purification, Physiological Function, and Applications

γ-Aminobutyric acid (GABA) is an important nonprotein amino acid that extensively exists in nature. At present, GABA is mainly obtained through chemical synthesis, plant enrichment, and microbial production, among which microbial production has received widespread attention due to its safety and environmental benefits. After using microbial fermentation to obtain GABA, it is necessary to be isolated and purified to ensure its quality and suitability for various industries such as food, agriculture, livestock, pharmaceutics, and others. This article provides a comprehensive review of the different sources of GABA, including its presence in nature and the synthesis methods. The factors affecting the production of microbial-derived GABA and its isolation and purification methods are further elucidated. Moreover, the main physiological functions of GABA and its application in different fields are also reviewed. By advancing our understanding of GABA, we can unlock its full potential and further utilize it in various fields to improve human health and well-being.

Crop adaptation to climate change: An evolutionary perspective

The disciplines of evolutionary biology and plant and animal breeding have been intertwined throughout their development, with responses to artificial selection yielding insights into the action of natural selection and evolutionary biology providing statistical and conceptual guidance for modern breeding. Here we offer an evolutionary perspective on a grand challenge of the 21st century: feeding humanity in the face of climate change. We first highlight promising strategies currently under way to adapt crops to current and future climate change. These include methods to match crop varieties with current and predicted environments and to optimize breeding goals, management practices, and crop microbiomes to enhance yield and sustainable production. We also describe the promise of crop wild relatives and recent technological innovations such as speed breeding, genomic selection, and genome editing for improving environmental resilience of existing crop varieties or for developing new crops. Next, we discuss how methods and theory from evolutionary biology can enhance these existing strategies and suggest novel approaches. We focus initially on methods for reconstructing the evolutionary history of crops and their pests and symbionts, because such historical information provides an overall framework for crop-improvement efforts. We then describe how evolutionary approaches can be used to detect and mitigate the accumulation of deleterious mutations in crop genomes, identify alleles and mutations that underlie adaptation (and maladaptation) to agricultural environments, mitigate evolutionary trade-offs, and improve critical proteins. Continuing feedback between the evolution and crop biology communities will ensure optimal design of strategies for adapting crops to climate change.

Use of metal nanoparticles in agriculture. A review on the effects on plant germination

Agricultural nanotechnology has become a powerful tool to help crops and improve agricultural production in the context of a growing world population. However, its application can have some problems with the development of harvests, especially during germination. This review evaluates nanoparticles with essential (Cu, Fe, Ni and Zn) and non-essential (Ag and Ti) elements on plant germination. In general, the effect of nanoparticles depends on several factors (dose, treatment time, application method, type of nanoparticle and plant). In addition, pH and ionic strength are relevant when applying nanoparticles to the soil. In the case of essential element nanoparticles, Fe nanoparticles show better results in improving nutrient uptake, improving germination, and the possibility of magnetic properties could favor their use in the removal of pollutants. In the case of Cu and Zn nanoparticles, they can be beneficial at low concentrations, while their excess presents toxicity and negatively affects germination. About nanoparticles of non-essential elements, both Ti and Ag nanoparticles can be helpful for nutrient uptake. However, their potential effects depend highly on the crop type, particle size and concentration. Overall, nanotechnology in agriculture is still in its early stages of development, and more research is needed to understand potential environmental and public health impacts.

Exploring the potential of halotolerant bacteria from coastal regions to mitigate salinity stress in wheat: physiological, molecular, and biochemical insights

Salinity stress, a significant global abiotic stress, is caused by various factors such as irrigation with saline water, fertilizer overuse, and drought conditions, resulting in reduced agricultural production and sustainability. In this study, we investigated the use of halotolerant bacteria from coastal regions characterized by high salinity as a solution to address the major environmental challenge of salinity stress. To identify effective microbial strains, we isolated and characterized 81 halophilic bacteria from various sources, such as plants, rhizosphere, algae, lichen, sea sediments, and sea water. We screened these bacterial strains for their plant growth-promoting activities, such as indole acetic acid (IAA), phosphate solubilization, and siderophore production. Similarly, the evaluation of bacterial isolates through bioassay revealed that approximately 22% of the endophytic isolates and 14% of rhizospheric isolates exhibited a favorable influence on seed germination and seedling growth. Among the tested isolates, GREB3, GRRB3, and SPSB2 displayed a significant improvement in all growth parameters compared to the control. As a result, these three isolates were utilized to evaluate their efficacy in alleviating the negative impacts of salt stress (150 mM, 300 mM, and seawater (SW)) on the growth of wheat plants. The result showed that shoot length significantly increased in plants inoculated with bacterial isolates up to 15% (GREB3), 16% (GRRB3), and 24% (SPSB2), respectively, compared to the control. The SPSB2 strain was particularly effective in promoting plant growth and alleviating salt stress. All the isolates exhibited a more promotory effect on root length than shoot length. Under salt stress conditions, the GRRB3 strain significantly impacted root length, leading to a boost of up to 6%, 5%, and 3.8% at 150 mM, 300 mM, and seawater stress levels, respectively. The bacterial isolates also positively impacted the plant's secondary metabolites and antioxidant enzymes. The study also identified the WDREB2 gene as highly upregulated under salt stress, whereas DREB6 was downregulated. These findings demonstrate the potential of beneficial microbes as a sustainable approach to mitigate salinity stress in agriculture.

Biostimulants and environmental stress mitigation in crops: A novel and emerging approach for agricultural sustainability under climate change

Pesticide and fertilizer usage is at the center of agricultural production to meet the demands of an ever-increasing global population. However, rising levels of chemicals impose a serious threat to the health of humans, animals, plants, and even the entire biosphere because of their toxic effects. Biostimulants offer the opportunity to reduce the agricultural chemical footprint owing their multilevel, beneficial properties helping to make agriculture more sustainable and resilient. When applied to plants or to the soil an increased absorption and distribution of nutrients, tolerance to environmental stress, and improved quality of plant products explain the mechanisms by which these probiotics are useful. In recent years, the use of plant biostimulants has received widespread attention across the globe as an ecologically acceptable alternative to sustainable agricultural production. As a result, their worldwide market continues to grow, and further research will be conducted to broaden the range of the products now available. Through this review, we present a current understanding of biostimulants, their mode of action and their involvement in modulating abiotic stress responses, including omics research, which may provide a comprehensive assessment of the crop's response by correlating molecular changes to physiological pathways activated under stress conditions aggravated by climate change.

Spatially resolved detection of small molecules from press-dried plant tissue using MALDI imaging

Premise

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is a chemical imaging method that can visualize spatial distributions of particular molecules. Plant tissue imaging has so far mostly used cryosectioning, which can be impractical for the preparation of large-area imaging samples, such as full flower petals. Imaging unsectioned plant tissue presents its own difficulties in extracting metabolites to the surface due to the waxy cuticle.

Methods

We address this by using established delipidation techniques combined with a solvent vapor extraction prior to applying the matrix with many low-concentration sprays.

Results

Using this procedure, we imaged tissue from three different plant species (two flowers and one carnivorous plant leaf). Material factorization analysis of the resulting data reveals a wide range of plant-specific small molecules with varying degrees of localization to specific portions of the tissue samples, while facilitating detection and removal of signal from background sources.

Conclusions

This work demonstrates applicability of MALDI-MSI to press-dried plant samples without freezing or cryosectioning, setting the stage for spatially resolved molecule identification. Increased mass resolution and inclusion of tandem mass spectrometry are necessary next steps to allow more specific and reliable compound identification.

Physiological and biochemical roles of ascorbic acid on mitigation of abiotic stresses in plants

Under conditions of abiotic stress several physiological and biochemical processes in plants can be modified. The production of reactive oxygen species (ROS) is toxic at high concentrations and promotes RNA, DNA and plant cell membrane degradation. Plants have enzymatic and non-enzymatic adaptation mechanisms to act against ROS detoxification. Ascorbic acid (AsA) is the non-enzymatic compound essential for several biological functions, which acts in the elimination and balance of ROS production and with the potential to promote several physiological functions in plants, such as the photosynthetic process. For plant development, AsA plays an important role in cell division, osmotic adjustment, hormone biosynthesis, and as an enzymatic cofactor. In this review, the redox reactions, biosynthetic pathways, and the physiological and biochemical functions of AsA against abiotic stress in plants are discussed. The concentration of AsA in plants can vary between species and depend on the biosynthetic pathways d-mannose/l-galactose, d-galacturonate, euglenids, and d-glucuronate. Although the endogenous levels of AsA in plants are used in large amounts in cell metabolism, the exogenous application of AsA further increases these endogenous levels to promote the antioxidant system and ameliorate the effects produced by abiotic stress. Foliar application of AsA promotes antioxidant metabolism in plants subjected to climate change conditions, also allowing the production of foods with higher nutritional quality and food safety, given the fact that AsA is biologically essential in the human diet.

Proline Enhances Resistance and Recovery of Oilseed Rape after a Simulated Prolonged Drought

This study was carried out to evaluate the effect of exogenous proline on the growth, biochemical responses, and plant recovery of drought-stressed oilseed rape plants after renewed irrigation. The experiment was conducted under controlled laboratory conditions. After 21 days of cultivation, 3-4 leaf stage seedlings were sprayed with proline (1 mM), then subjected to prolonged drought stress for 8 days to achieve a severe water deficit, next, irrigation was resumed and recovery was assessed after 4 days. The results show that exogenous application of proline reduced the drought-induced growth inhibition of seedlings while maintaining relative water content (RWC) and growth parameters closer to those of irrigated plants. Proline had a positive effect on chlorophyll accumulation and membrane permeability while decreasing ethylene, H₂O₂, and MDA levels. Moreover, after 4 days of recovery, the H₂O₂ content of the proline-treated plants was significantly lower (2-fold) and the MDA content was close to that of continuously irrigated plants. Thus, all these biochemical reactions influenced plant survival: after drought + proline treatment, the number of surviving plants was two times higher than that of drought-treated plants. The findings show that exogenous proline has antioxidant, osmotic, and growth-promoting properties that improve the drought tolerance of winter oilseed rape plants and is, therefore, beneficial for drought adaptation in oilseed rape.

Plant lectins: Classical molecules with emerging roles in stress tolerance

Biotic and abiotic stresses impose adverse effects on plant's development, growth, and production. For the past many years, researchers are trying to understand the stress induced responses in plants and decipher strategies to produce stress tolerant crops. It has been demonstrated that molecular networks encompassing an array of genes and functional proteins play a key role in generating responses to combat different stresses. Newly, there has been a resurgence of interest to explore the role of lectins in modulating various biological responses in plants. Lectins are naturally occurring proteins that form reversible linkages with their respective glycoconjugates. To date, several plant lectins have been recognized and functionally characterized. However, their involvement in stress tolerance is yet to be comprehensively analyzed in greater detail. The availability of biological resources, modern experimental tools, and assay systems has provided a fresh impetus for plant lectin research. Against this backdrop, the present review provides background information on plant lectins and recent knowledge on their crosstalks with other regulatory mechanisms, which play a remarkable role in plant stress amelioration. It also highlights their versatile role and suggests that adding more information to this under-explored area will usher in a new era of crop improvement.

The resilient cotton plant: uncovering the effects of stresses on secondary metabolomics and its underlying molecular mechanisms

Cotton is an important fiber crop cultivated around the world under diverse climate conditions and generates billions of dollars in annual revenue globally. Biotic and abiotic stresses have caused reduction in yield and productivity of cotton crops. In this review, we comprehensively analyzed and summarized the effect of biotic and abiotic stress on secondary metabolite production in cotton. The development of cotton varieties with improved tolerance against abiotic and biotic stress can play an important role in sustainable cotton production. Under stress conditions, plants develop a variety of defense mechanisms such as initiating signaling functions to upregulate defense responsive genes and accumulation of secondary metabolites. Understanding the impact of stress on secondary metabolite production in cotton is crucial for developing strategies to alleviate the negative effects of stress on crop yield and quality. Further, the potential industrial applications of these secondary metabolites in cotton, such as gossypol, could provide new opportunities for sustainable cotton production and the development of value-added products. Additionally, transgenic and genome-edited cotton cultivars can be developed to provide tolerance to both abiotic and biotic stress in cotton production.

Efficient strategies for controlled release of nanoencapsulated phytohormones to improve plant stress tolerance

Climate change due to different human activities is causing adverse environmental conditions and uncontrolled extreme weather events. These harsh conditions are directly affecting the crop areas, and consequently, their yield (both in quantity and quality) is often impaired. It is essential to seek new advanced technologies to allow plants to tolerate environmental stresses and maintain their normal growth and development. Treatments performed with exogenous phytohormones stand out because they mitigate the negative effects of stress and promote the growth rate of plants. However, the technical limitations in field application, the putative side effects, and the difficulty in determining the correct dose, limit their widespread use. Nanoencapsulated systems have attracted attention because they allow a controlled delivery of active compounds and for their protection with eco-friendly shell biomaterials. Encapsulation is in continuous evolution due to the development and improvement of new techniques economically affordable and environmentally friendly, as well as new biomaterials with high affinity to carry and coat bioactive compounds. Despite their potential as an efficient alternative to phytohormone treatments, encapsulation systems remain relatively unexplored to date. This review aims to emphasize the potential of phytohormone treatments as a means of enhancing plant stress tolerance, with a specific focus on the benefits that can be gained through the improved exogenous application of these treatments using encapsulation techniques. Moreover, the main encapsulation techniques, shell materials and recent work on plants treated with encapsulated phytohormones have been compiled.

Antibiotics induced changes in nitrogen metabolism and antioxidative enzymes in mung bean (Vigna radiata)

Excessive use and release of antibiotics into the soil environment in the developing world have resulted in altered soil processes affecting terrestrial organisms and posing a serious threat to crop growth and productivity. The present study investigated the influence of exogenously applied oxytetracycline (OXY) and levofloxacin (LEV) on plant physiological responses, key enzymes involved in nitrogen metabolism (e.g., nitrate reductase, glutamine synthetase), nitrogen contents and oxidative stress response of mung bean (Vigna radiata). Plants were irrigated weekly with antibiotics containing water for exposing the plants to different concentrations i.e., 1, 10, 20, 50, and 100 mg L^-1. Results showed a significant decrease in nitrate reductase activity in both antibiotic treatments and their mixtures and increased antioxidant enzymatic activities in plants. At lower concentrations of antibiotics (≤20 mg L^-1), 53.9 % to 78.4 % increase in nitrogen content was observed in levofloxacin and mixtures compared to the control, resulting in an increase in the overall plant biomass. Higher antibiotic (≥50 mg L^-1) concentration showed 58 % decrease in plant biomass content and an overall decrease in plant nitrogen content upon exposure to the mixtures. This was further complemented by 22 % to 42 % increase in glutamine synthetase activity observed in the plants treated with levofloxacin and mixtures. The application of low doses of antibiotics throughout the experiments resulted in lower toxicity symptoms in the plants. However, significantly higher malondialdehyde (MDA) concentrations at higher doses (20 mg L^-1 and above) than the control showed that plants' tolerance against oxidative stress was conceded with increasing antibiotic concentrations. The toxicity trend was: levofloxacin > mixture > oxytetracycline.

Silicic and Ascorbic Acid Induced Modulations in Photosynthetic, Mineral Uptake, and Yield Attributes of Mung Bean (Vigna radiata L. Wilczek) under Ozone Stress

Most of the world's crop production and plant growth are anticipated to be seriously threatened by the increasing tropospheric ozone (O₃) levels. The current study demonstrates how different mung bean genotypes reacted to the elevated level of O₃ in the presence of exogenous ascorbic and silicic acid treatments. It is the first report to outline the potential protective effects of ascorbic and silicic acid applications against O₃ toxicity in 12 mung bean {Vigna radiata (L.) Wilken} varieties. Under controlled circumstances, the present investigation was conducted in a glass house. There were four different treatments used: control (ambient O₃ concentration of 40-45 ppb), elevated O₃ (120 ppb), elevated O₃ with silicic acid (0.1 mM), and elevated O₃ with ascorbic acid (10 mM). Three varieties, viz. NM 20-21, NM 2006, and NM 2016, showcased tolerance to O₃ toxicity. Our findings showed that ascorbic and silicic acid applications gradually increased yield characteristics such as seed yield, harvest index, days to maturity, and characteristics related to gas exchange such as transpiration rate, stomatal conductance, net photosynthetic activity, and water-use efficiency. Compared to the control, applying both growth regulators enhanced the mineral uptake across all treatments. Based on the findings of the current study, it is concluded that the subject mung bean genotypes responded to silicic acid treatment more efficiently than ascorbic acid to mitigate the harmful effects of O₃ stress.

Floret Biofortification of Broccoli Using Amino Acids Coupled with Selenium under Different Surfactants: A Case Study of Cultivating Functional Foods

Broccoli serves as a functional food because it can accumulate selenium (Se), well-known bioactive amino-acid-derived secondary metabolites, and polyphenols. The chemical and physical properties of Se are very similar to those of sulfur (S), and competition between sulfate and selenate for uptake and assimilation has been demonstrated. Towards an efficient agronomic fortification of broccoli florets, the working questions were whether we could overcome this competition by exogenously applying the S-containing amino acids cysteine (Cys) or/and methionine (Met), or/and the precursors of Glucosinolate (GSL) types along with Se application. Broccoli plants were cultivated in a greenhouse and at the beginning of floret growth, we exogenously applied sodium selenate in the concentration gradient of 0, 0.2, 1.5, and 3.0 mM to study the impact of increased Se concentration on the organic S (S_org) content of the floret. The Se concentration of 0.2 mM (Se0.2) was coupled with the application of Cys, Met, their combination, or a mixture of phenylalanine, tryptophane, and Met. The application took place through fertigation or foliar application (FA) by adding isodecyl alcohol ethoxylate (IAE) or a silicon ethoxylate (SiE) surfactant. Fresh biomass, dry mass, and Se accumulation in florets were evaluated, along with their contents of S_org, chlorophylls (Chl), carotenoids (Car), glucoraphanin (GlRa), glucobrassicin (GlBra), glucoiberin (GlIb), and polyphenols (PPs), for the biofortification efficiency of the three application modes. From the studied selenium concentration gradient, the foliar application of 0.2 mM Se using silicon ethoxylate (SiE) as a surfactant provided the lowest commercially acceptable Se content in florets (239 μg or 0.3 μmol g^-1 DM); it reduced S_org (-45%), GlIb (-31%), and GlBr (-27%); and it increased Car (21%) and GlRa (27%). Coupled with amino acids, 0.2 mM Se provided commercially acceptable Se contents per floret only via foliar application. From the studied combinations, that of Met,Se0.2/FA,IAE provided the lowest Se content per floret (183 μg or 0.2 μmol g^-1 DM) and increased S_org (35%), Car (45%), and total Chl (27%), with no effect on PPs or GSLs. Cys,Met,Se0.2/FA,IAE and amino acid mix,Se0.2/FA,IAE increased S_org content, too, by 36% and 16%, respectively. Thus, the foliar application with the IAE surfactant was able to increase S_org, and methionine was the amino acid in common in these treatments, with varying positive effects on carotenoids and chlorophylls. Only the Cys,Met,Se0.2 combination presented positive effects on GSLs, especially GlRa, but it reduced the fresh mass of the floret. The foliar application with SiE as a surfactant failed to positively affect the organic S content. However, in all studied combinations of Se 0.2 mM with amino acids, the Se content per floret was commercially acceptable, the yield was not affected, the content of GSLs was increased (especially that of GlRa and GlIb), and PPs were not affected. The content of GlBr decreased except for the treatment with methionine (Met,Se0.2/FA,SiE) where GlBr remained unaffected. Hence, the combination of Se with the used amino acids and surfactants can provide enhanced biofortification efficiency in broccoli by providing florets as functional foods with enhanced functional properties.

Paper-Based Multiplex Sensors for the Optical Detection of Plant Stress

The rising population and the ongoing climate crisis call for improved means to monitor and optimise agriculture. A promising approach to tackle current challenges in food production is the early diagnosis of plant diseases through non-invasive methods, such as the detection of volatiles. However, current devices for detection of multiple volatiles are based on electronic noses, which are expensive, require complex circuit assembly, may involve metal oxides with heating elements, and cannot easily be adapted for some applications that require miniaturisation or limit front-end use of electronic components. To address these challenges, a low-cost optoelectronic nose using chemo-responsive colorimetric dyes drop-casted onto filter paper has been developed in the current work. The final sensors could be used for the quantitative detection of up to six plant volatiles through changes in colour intensities with a sub-ppm level limit of detection, one of the lowest limits of detection reported so far using colorimetric gas sensors. Sensor colouration could be analysed using a low-cost spectrometer and the results could be processed using a microcontroller. The measured volatiles could be used for the early detection of plant abiotic stress as early as two days after exposure to two different stresses: high salinity and starvation. This approach allowed a lowering of costs to GBP 1 per diagnostic sensing paper. Furthermore, the small size of the paper sensors allows for their use in confined settings, such as Petri dishes. This detection of abiotic stress could be easily achieved by exposing the devices to living plants for 1 h. This technology has the potential to be used for monitoring of plant development in field applications, early recognition of stress, implementation of preventative measures, and mitigation of harvest losses.

The multifaceted roles of Arbuscular Mycorrhizal Fungi in peanut responses to salt, drought, and cold stress

BACKGROUND

Arbuscular Mycorrhizal Fungi (AMF) are beneficial microorganisms in soil-plant interactions; however, the underlying mechanisms regarding their roles in legumes environmental stress remain elusive. Present trials were undertaken to study the effect of AMF on the ameliorating of salt, drought, and cold stress in peanut (Arachis hypogaea L.) plants. A new product of AMF combined with Rhizophagus irregularis SA, Rhizophagus clarus BEG142, Glomus lamellosum ON393, and Funneliformis mosseae BEG95 (1: 1: 1: 1, w/w/w/w) was inoculated with peanut and the physiological and metabolomic responses of the AMF-inoculated and non-inoculated peanut plants to salt, drought, and cold stress were comprehensively characterized, respectively.

RESULTS

AMF-inoculated plants exhibited higher plant growth, leaf relative water content (RWC), net photosynthetic rate, maximal photochemical efficiency of photosystem II (PSII) (Fv/Fm), activities of antioxidant enzymes, and K⁺: Na⁺ ratio while lower leaf relative electrolyte conductivity (REC), concentration of malondialdehyde (MDA), and the accumulation of reactive oxygen species (ROS) under stressful conditions. Moreover, the structures of chloroplast thylakoids and mitochondria in AMF-inoculated plants were less damaged by these stresses. Non-targeted metabolomics indicated that AMF altered numerous pathways associated with organic acids and amino acid metabolisms in peanut roots under both normal-growth and stressful conditions, which were further improved by the osmolytes accumulation data.

CONCLUSION

This study provides a promising AMF product and demonstrates that this AMF combination could enhance peanut salt, drought, and cold stress tolerance through improving plant growth, protecting photosystem, enhancing antioxidant system, and regulating osmotic adjustment.

Salinity stress endurance of the plants with the aid of bacterial genes

The application of plant growth-promoting bacteria (PGPB) is vital for sustainable agriculture with continuous world population growth and an increase in soil salinity. Salinity is one of the severe abiotic stresses which lessens the productivity of agricultural lands. Plant growth-promoting bacteria are key players in solving this problem and can mitigate salinity stress. The highest of reported halotolerant Plant growth-promoting bacteria belonged to Firmicutes (approximately 50%), Proteobacteria (40%), and Actinobacteria (10%), respectively. The most dominant genera of halotolerant plant growth-promoting bacteria are Bacillus and Pseudomonas. Currently, the identification of new plant growth-promoting bacteria with special beneficial properties is increasingly needed. Moreover, for the effective use of plant growth-promoting bacteria in agriculture, the unknown molecular aspects of their function and interaction with plants must be defined. Omics and meta-omics studies can unreveal these unknown genes and pathways. However, more accurate omics studies need a detailed understanding of so far known molecular mechanisms of plant stress protection by plant growth-promoting bacteria. In this review, the molecular basis of salinity stress mitigation by plant growth-promoting bacteria is presented, the identified genes in the genomes of 20 halotolerant plant growth-promoting bacteria are assessed, and the prevalence of their involved genes is highlighted. The genes related to the synthesis of indole acetic acid (IAA) (70%), siderophores (60%), osmoprotectants (80%), chaperons (40%), 1-aminocyclopropane-1-carboxylate (ACC) deaminase (50%), and antioxidants (50%), phosphate solubilization (60%), and ion homeostasis (80%) were the most common detected genes in the genomes of evaluated halotolerant plant growth-promoting and salinity stress-alleviating bacteria. The most prevalent genes can be applied as candidates for designing molecular markers for screening of new halotolerant plant growth-promoting bacteria.

Subcellular distribution and physiological responses of native and exotic grasses from the Pampa biome subjected to excess manganese

Fungicides containing manganese (Mn) applied to control plant diseases increase the concentration of Mn in soils, which may potentiate Mn toxicity in acid soils. Some species of wild grasses, such as those from the Pampa biome located in South America, or even those introduced into this biome, may possess different mechanisms of tolerance to excess Mn. The present study aimed to evaluate the subcellular distribution and physiological and biochemical responses of exotic and native grasses from the Pampa biome, cultivated in Mn excess. The experiment was conducted in nutrient solution in a greenhouse, in an entirely randomized design, bifactorial 4 × 4, consisting of four Mn concentrations (2 [control], 300, 600 and 900 μM) and four species (two exotic: Avena strigosa and Lolium multiflorum; and two native: Paspalum notatum and Paspalum plicatulum). At 27 days of exposure to the treatments, biomass and growth rates, leaf gas exchange with the environment, photosynthetic pigment concentrations of malondialdehyde and H2O2, antioxidant enzyme activities (SOD and POD), and subcellular distribution of Mn were evaluated. Most of the grasses showed high concentration of Mn in tissues, mainly, in the shoot. In the presence of 900 μM Mn, more than 80% of the absorbed Mn was compartmentalized in the cell walls and vacuoles of the cells. Compartmentalization of Mn excess into metabolically less active organelles is the main tolerance factor in grasses. Physiological and biochemical responses were stimulated in the presence of 300 μM Mn, while 900 μM Mn negatively affected biochemical-physiological responses of grasses. The species L. multiflorum was most sensitive to excess Mn, while P. notatum was the most tolerant.

Warhorses in soil bioremediation: Seed biopriming with PGPF secretome to phytostimulate crop health under heavy metal stress

The fungal symbiosis with the plant root system is importantly recognized as a plant growth promoting fungi (PGPFs), as well as elicitor of plant defence against different biotic and abiotic stress conditions. Thus PGPFs are playing as a key trouper in enhancing agricultural quality and increased crop production and paving a way towards a sustainable agriculture. Due to increased demand of food production, the over and unscientific usage of chemical fertilizers has led to the contamination of soil by organic and inorganic wastes impacting on soil quality, crops quality effecting on export business of agricultural products. The application of microbial based consortium like plant growth promoting fungi is gaining worldwide importance due to their multidimensional activity. These activities are through plant growth promotion, induction of systemic resistance, disease combating and detoxification of organic and inorganic toxic chemicals, a heavy metal tolerance ability. The master key behind these properties exhibited by PGPFs are attributed towards various secretory biomolecules (secondary metabolites or enzymes or metabolites) secreted by the fungi during interaction mechanism. The present review is focused on the multidimensional role PGPFs as elicitors of Induced systemic resistance against phytopathogens as well as heavy metal detoxifier through seed biopriming and biofortification methods. The in-sights on PGPFs and their probable mechanistic nature contributing towards plants to withstand heavy metal stress and stress alleviation by activating of various stress regulatory pathways leading to secretion of low molecular weight compounds like organic compounds, glomalin, hydrophobins, etc,. Thus projecting the importance of PGPFs and further requirement of research in developing PGPFs based molecules and combining with trending Nano technological approaches for enhanced heavy metal stress alleviations in plant and soil as well as establishing a sustainable agriculture.

Seed nanopriming: How do nanomaterials improve seed tolerance to salinity and drought?

Salt and drought stress are major environmental issues world-widely. These stresses can result in failures of seed germination, limiting agricultural production. New approaches are needed to increase crop production, ensuring food safety, quality, and agriculture sustainability. Nanopriming (priming seeds with nanomaterials) is an emerging seed technology improving crop production under the drastic climate change associated with stress factors. The present review not only provided an overview of nanopriming achieved salt and drought tolerance but also tried to discuss the behind mechanisms. We argued that the physico-chemical properties of the nanomaterials are key factors affecting their negative or positive effects on seed germination in terms of seed nanopriming. Furthermore, we highlighted the possible critical role of seed coat anatomy in effective nanopriming, in terms of saving costs and reducing biosafety issues. This review aims to help researchers to better understand and follow this fast-developing, cost-effective, and environmentally friendly research area.

Nontargeted metabolomic analysis to unravel alleviation mechanisms of carbon nanotubes on inhibition of alfalfa growth under pyrene stress

Carbon nanotubes have displayed great potential in enhancing phytoremediation of PAHs polluted soils. However, the response of plants to the coexistence of carbon nanotubes and PAHs and the associated influencing mechanisms remain largely unknown. Here, the effect of carbon nanotubes on alfalfa growth and pyrene uptake under exposure to pyrene was evaluated through sand culture experiment and gas chromatography time-of-flight mass spectrometer (GC-TOF-MS) based metabolomics. Results showed that pyrene at 10 mg kg^-1 obviously reduced the shoot fresh weight of alfalfa by 18.3 %. Multiwall carbon nanotubes (MWCNTs) at 25 and 50 mg kg^-1 significantly enhanced the shoot fresh weight in a dose-dependent manner, nearly by 80 % at 50 mg kg^-1. Pyrene was mainly accumulated in alfalfa roots, in which the concentration was 35 times as much as that in shoots. MWCNTs greatly enhanced the accumulation of pyrene in alfalfa roots, almost by two times at 50 mg kg^-1, while decreased pyrene concentration in shoots, from 0.11 mg kg^-1 to 0.044 mg kg^-1 at MWCNTs concentration of 50 mg kg^-1. Metabolomics data revealed that pyrene at 10 mg kg^-1 trigged significant metabolic changes in alfalfa root exudates, downregulating 27 metabolites. MWCNTs generated an increase in the contents of some downregulated metabolites caused by pyrene stress, which were restored to the original level or even higher, mainly including organic acids and amino acids. MWNCTs significantly enriched some metabolic pathways positively correlated with shoot growth and pyrene accumulation in shoots under exposure to pyrene, including TCA cycle, glyoxylate and dicarboxylate metabolism, cysteine and methione metabolism as well as alanine, aspartate and glutamate metabolism. This work highlights the regulation effect of MWCNTs on the metabolism of root exudates, which are helpful for alfalfa to alleviate the stress from pyrene contamination.

Amelioration of lead toxicity by ascorbic acid in sugarcane (Saccharum officinarum L.) under in vitro condition

Agricultural sites are polluted with various metal ions worldwide. Ascorbic acid (AA) plays diverse roles in plant growth, development, and the regulation of cellular mechanisms against environmental stress. This study provides the relationship between morphological and biochemical parameters involved in the amelioration of Pb toxicity in three sugarcane (Saccharum officinarum L.) genotypes (YT-53, CP-77-400, NSG-59) by using six concentrations of Pb(NO₃)₂ under in vitro conditions. Morphological and biochemical parameters of ascorbic acid pretreated and non-pretreated calli were compared at each Pb(NO₃)₂ concentration. Ascorbic acid-pretreated calli have better callus growth and regeneration potential than non-treated calli under increased Pb concentration. Biochemical parameters such as antioxidant enzyme activity (peroxidase (POD), superoxide dismutase (SOD), catalase (CAT)) increased under increased Pb concentration. Ascorbic acid pretreatment further enhanced the POD and SOD activity, while CAT activity and total soluble protein contents of pretreated calli did not change significantly. Ascorbic acid ameliorated the Pb toxicity morphologically but showed uneven behavior towards biochemical parameters. Different genotypic behaviors versus different treatments were also observed. In the future, information from this study can be used to develop the metal-resistant sugarcane genotype against metal stress under in vitro conditions.

Metabolites produced by inoculated Vigna radiata during bacterial assisted phytoremediation of Pb, Ni and Cr polluted soil

Phytoremediation assisted with plant growth promoting bacteria (PGPB) is a green technology to remediate metal contaminated soils. Plants usually produce secondary metabolites to tolerate metal toxicity. Present study was designed to explore the phytoremediation potential of Vigna radiata var. NM-II in the presence of metal resistant PGPB and comparison of metabolites produced under heavy metal stresses (Pb, Ni, Cr). Three PGPB selected for present study include Bacillus pumilus MB246, Serratia nematodiphila MB307 and Delftia Lacustris MB322. Pot experiments were conducted with inoculated V. radiata NM-II seeds grown in soil artificially contaminated with lead (Pb), Nickle (Ni) and chromium (Cr) at a concentration of 300, 200 and 100 mg/kg respectively. After harvesting various growth parameters were studied (root length, shoot length, fresh weight and dry weight). Bacterial colonization on root surfaces of harvested plants was observed through Scanning electron microscopy (SEM) and Elemental composition was recorded through Energy dispersive X-ray spectroscopy (EDX) attached with SEM. Metabolic response of harvested plants was studied through Gas chromatography Mass spectrophotometry (GC-MS) analysis. Metal accumulation in roots, shoots and soil was analysed by acid digestion method from which Bioaccumulation factor (BF) and Translocation factor (TF) of metal from soil to plant was calculated. Results revealed stimulatory effect of PGPB on growth and phytoextraction ability of V. radiata. Soil metal removal efficiency was in the order Pb>Ni>Cr, whereas metal distribution in each part of plant was root>stem>leaf. The BF and TF values suggested V. radiata as Pb and Ni excluder while moderate accumulator for Cr. Elemental analysis through Energy Dispersive X- ray spectroscopy (EDX) found potassium (K+)and calcium (Ca+)as highly abundant nutrients with least accumulation of sulphur (S). Metabolites study through GC-MS revealed variety of compounds (carbohydrates, amino acids, fatty acids, steroids etc) detected differentially under each metal treatment and their concentration was influenced by different bacterial inoculations. Overall 9-Octadecenamide was found as commonly present lipid compound in most of the treatments which is required for detoxification in plants. The study concluded beneficial role of PGPB for successful phytoremediation of heavy metals and differential response of metabolites towards each metal stress that is related to metal tolerance ability of V. radiata.

Fe2O3-modified graphene oxide mitigates nanoplastic toxicity via regulating gas exchange, photosynthesis, and antioxidant system in Triticum aestivum

The ever-increasing plastic pollution in soil and water resources raises concerns about its effects on terrestrial plants and agroecosystems. Although there are many reports about the contamination with nanoplastics on plants, the presence of magneto-assisted nanomaterials enabling the removal of their adverse impacts still remains unclear. Therefore, the purpose of the current study is to evaluate the potential of nanomaterial Fe₂O₃-modified graphene oxide (FGO, 50-250 mg L^-1) to eliminate the adverse effects of nanoplastics in plants. Wheat plants exposed to polystyrene nanoplastics concentrations (PS, 10, 50 and 100 mg L^-1) showed decreased growth, water content and loss of photosynthetic efficiency. PS toxicity negatively altered gas exchange, antenna structure and electron transport in photosystems. Although the antioxidant system was partially activated (only superoxide dismutase (SOD), NADPH oxidase (NOX) and glutathione reductase (GR)) in plants treated with PS, it failed to prevent PS-triggered oxidative damage, as showing lipid peroxidation and hydrogen peroxide (H₂O₂) levels. FGOs eliminated the adverse impacts of PS pollution on growth, water status, gas exchange and oxidative stress markers. In addition, FGOs preserve the biochemical reactions of photosynthesis by actively increasing chlorophyll fluorescence parameters in the stressed-wheat leaves. The activities of all enzymatic antioxidants increased, and the H₂O₂ and TBARS contents decreased. GSH-mediated detoxifying antioxidants such as glutathione S-transferase (GST) and glutathione peroxidase (GPX) were stimulated by FGOs against PS pollution. FGOs also triggered the enzymes and non-enzymes related to the Asada-Halliwell cycle and protected the regeneration of ascorbate (AsA) and glutathione (GSH). Our findings indicated that FGO had the potential to mitigate nanoplastic-induced damage in wheat by regulating water relations, protecting photosynthesis reactions and providing efficient ROS scavenging with high antioxidant capacity. This is the first report on removing PS-induced damage by FGO applications in wheat leaves.

Ectopic expression of NAC transcription factor HaNAC3 from Haloxylon ammodendron increased abiotic stress resistance in tobacco

HaNAC3 is a transcriptional activator located in the nucleus that may be involved in the response to high temperature, high salt and drought stresses as well as phytohormone IAA and ABA treatments. Our study demonstrated that HaNAC3 increased the tolerance of transgenic tobacco to abiotic stress and was involved in the regulation of a range of downstream genes and metabolic pathways. This also indicates the potential application of HaNAC3 as a plant tolerance gene. NAC transcription factors play a key role in plant growth and development and plant responses to biotic and abiotic stresses. However, the biological functions of NAC transcription factors in the desert plant Haloxylon ammodendron are still poorly understood. In this study, the NAC transcription factor HaNAC3 was isolated and cloned from a typical desert plant H. ammodendron, and its possible biological functions were investigated. Bioinformatics analysis showed that HaNAC3 has the unique N-terminal NAC structural domain of NAC transcription factor. Quantitative real-time fluorescence analysis showed that HaNAC3 was able to participate in the response to simulated drought, high temperature, high salt, and phytohormone IAA and ABA treatments, and was very sensitive to simulated high temperature and phytohormone ABA treatments. Subcellular localization analysis showed that the GFP-HaNAC3 fusion protein was localized in the nucleus of tobacco epidermal cells. The transcriptional self-activation assay showed that HaNAC3 had transcriptional self-activation activity, and the truncation assay confirmed that the transcriptional activation activity was located at the C-terminus. HaNAC3 gene was expressed exogenously in wild-type Nicotiana benthamiana, and the physiological function of HaNAC3 was verified by simulating drought and other abiotic stresses. The results indicated that transgenic tobacco had better resistance to abiotic stresses than wild-type B. fuminata. Further transcriptome analysis showed that HaNAC3 was involved in the regulation of a range of downstream resistance genes, wax biosynthesis and other metabolic pathways. These results suggest that HaNAC3 may have a stress resistance role in H. ammodendron and has potential applications in plant molecular breeding.

Using Exogenous Melatonin, Glutathione, Proline, and Glycine Betaine Treatments to Combat Abiotic Stresses in Crops

Abiotic stresses, such as drought, salinity, heat, cold, and heavy metals, are associated with global climate change and hamper plant growth and development, affecting crop yields and quality. However, the negative effects of abiotic stresses can be mitigated through exogenous treatments using small biomolecules. For example, the foliar application of melatonin provides the following: it protects the photosynthetic apparatus; it increases the antioxidant defenses, osmoprotectant, and soluble sugar levels; it prevents tissue damage and reduces electrolyte leakage; it improves reactive oxygen species (ROS) scavenging; and it increases biomass, maintains the redox and ion homeostasis, and improves gaseous exchange. Glutathione spray upregulates the glyoxalase system, reduces methylglyoxal (MG) toxicity and oxidative stress, decreases hydrogen peroxide and malondialdehyde accumulation, improves the defense mechanisms, tissue repairs, and nitrogen fixation, and upregulates the phytochelatins. The exogenous application of proline enhances growth and other physiological characteristics, upregulates osmoprotection, protects the integrity of the plasma lemma, reduces lipid peroxidation, increases photosynthetic pigments, phenolic acids, flavonoids, and amino acids, and enhances stress tolerance, carbon fixation, and leaf nitrogen content. The foliar application of glycine betaine improves growth, upregulates osmoprotection and osmoregulation, increases relative water content, net photosynthetic rate, and catalase activity, decreases photorespiration, ion leakage, and lipid peroxidation, protects the oxygen-evolving complex, and prevents chlorosis. Chemical priming has various important advantages over transgenic technology as it is typically more affordable for farmers and safe for plants, people, and animals, while being considered environmentally acceptable. Chemical priming helps to improve the quality and quantity of the yield. This review summarizes and discusses how exogenous melatonin, glutathione, proline, and glycine betaine can help crops combat abiotic stresses.

Exogenous melatonin promotes the growth of alfalfa (Medicago sativa L.) under NaCl stress through multiple pathways

Salinity is one of the most common factors affecting alfalfa (Medicago sativa L.), and NaCl is one of the main factors of salinity stress which can cause heavy losses in agricultural production in the world. The application of exogenous melatonin (MT) plays a major role in numerous plants against various stress environments. The effects of exogenous MT on the NaCl tolerance of alfalfa treated with the control, 100 µmol L^-1 MT, 150 mmol L^-1 NaCl, or 150 mmol L^-1 NaCl+ 100 µmol L^-1 MT were investigated. The results showed that MT increased growth parameters, inhibited chlorophyll degradation and promoted photosynthetic gas exchange parameters (photosynthetic rate, conductance to H₂O, and transpiration rate) and stomatal opening under NaCl stress. Osmotic regulation substances such as soluble sugar, proline and glycine betaine were the highest in the NaCl treatment and the second in the NaCl+MT treatment. Nitrogen, phosphorus, potassium, calcium and magnesium were reduced and sodium was increased by NaCl, whereas these levels were reversed by the NaCl+MT treatment. MT inhibited cell membrane imperfection, lipid peroxidation and reactive oxygen species (ROS) accumulation caused by NaCl stress. MT up-regulated the gene expression and activity of antioxidant enzymes and increased the content of antioxidant non-enzyme substances to scavenge excessive ROS in NaCl-treated plants. In addition, all indicators interacted with each other to a certain extent and could be grouped according to the relative values. All variables were divided into PC 1 (89.2 %) and PC 2 (4 %). They were clustered into two categories with opposite effects, and most of them were significant variables. Hence, these findings reveal that exogenous MT alleviates the inhibitory effects of NaCl stress on photosynthesis, stomata opening, osmotic adjustment, ion balance and redox homeostasis, enhancing tolerance and growth of alfalfa. Furthermore, it suggests that MT could be implemented to improve the NaCl tolerance of alfalfa.

Feasibility of using melatonin content in pepper (Capsicum annuum) seeds as a physiological marker of chilling stress tolerance

The presence of melatonin, a known animal hormone, has been confirmed in many evolutionary distant organisms, including higher plants. It is known that melatonin increases tolerance to stress factors as a wide spectrum antioxidant. Tolerant genotypes have generally higher melatonin content than sensitive ones, and exposure to stressful conditions is known to increase endogenous melatonin levels. However, endogenous melatonin levels in seeds have never been used to select genotypes tolerant to abiotic stresses. Thus, in this study, the existence of possible relationship between seed melatonin levels of 28 pepper (Capsicum annuum L.) genotypes and their germination and emergence performance under chilling conditions (15°C) was investigated. The results indicated that these parameters were much better for pepper genotypes with higher seed melatonin contents while those having less than 2ngg-1 additionally exhibited elevated levels of MDA and H2 O2 but lower antioxidant enzyme activities. Thus, a positive relationship between seed melatonin content and chilling stress tolerance has been shown, suggesting a possible use of endogenous melatonin levels as a criterion in selecting chilling stress tolerant varieties. To save considerable time, money and labour, it is recommended that genotypes with lower melatonin contents are excluded from breeding programmes that aim to develop new stress tolerant genotypes.

Seed Priming with Carbon Nanomaterials Improves the Bioactive Compounds of Tomato Plants under Saline Stress

The consumption of food with a high content of bioactive compounds is correlated with the prevention of chronic degenerative diseases. Tomato is a food with exceptional nutraceutical value; however, saline stress severely affects the yield, the quality of fruits, and the agricultural productivity of this crop. Recent studies have shown that seed priming can mitigate or alleviate the negative effects caused by this type of stress. However, the use of carbon nanomaterials (CNMs) in this technique has not been tested for this purpose. In the present study, the effects of tomato seed priming with carbon nanotubes (CNTs) and graphene (GP) (50, 250, and 500 mg L−1) and two controls (not sonicated and sonicated) were evaluated based on the content of photosynthetic pigments in the leaves; the physicochemical parameters of the fruits; and the presence of enzymatic and non-enzymatic antioxidant compounds, carotenoids, and stress biomarkers such as hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the leaves and fruits of tomato plants without saline stress and with saline stress (50 mM NaCl). The results show that saline stress in combination with CNTs and GP increased the content of chlorophylls (9.1–21.7%), ascorbic acid (19.5%), glutathione (≈13%), proteins (9.9–11.9%), and phenols (14.2%) on the leaves. The addition of CNTs and GP increased the activity of enzymes (CAT, APX, GPX, and PAL). Likewise, there was also a slight increase in the content of H2O2 (by 20.5%) and MDA (3.7%) in the leaves. Salinity affected the quality of tomato fruits. The physico-chemical parameters and bioactive compounds in both the stressed and non-stressed tomato plants were modified with the addition of CNTs and GP. Higher contents of total soluble solids (25.9%), phenols (up to 144.85%), flavonoids (up to 37.63%), ascorbic acid (≈28%), and lycopene (12.4–36.2%) were observed. The addition of carbon nanomaterials by seed priming in tomato plants subjected to saline stress modifies the content of bioactive compounds in tomato fruits and improves the antioxidant defense system, suggesting possible protection of the plant from the negative impacts of stress by salinity. However, analysis of the mechanism of action of CNMs through seed priming, in greater depth is suggested, perhaps with the use of omics sciences.

OsSalT gene cloned from rice provides evidence of its role in salinity and drought stress tolerance

Abiotic stresses impose a huge threat to agricultural productivity and global food security. To counter this challenge, the precise identification of the right candidate gene (s) for conferring abiotic stress tolerance without compromising the growth and yield is crucial. OsSalT is identified as a salt stress responsive gene located on SalTol QTL of chromosome 1 of rice, however, there is no genetic evidence of its function and probable pathway of its regulation. To get better insights into its functioning, earlier we elucidated the structure of SALT protein at atomic scale {PDB ID (5GVY)} and solution state that provided key clues on the probable mode of its action. Herein, we report the modulation of OsSalT gene in response to various factors and its functional characterization. Results indicate that OsSalT operates through both abscisic acid and gibberellic acid-dependent pathways and is linked to the adaptive stress mechanisms of plants. Its overexpression in a model plant resulted in improved salinity and drought stress tolerance. The OsSalT transformed plants also showed vigorous root growth, early flowering, and better seed germination. The triggering of multiple responses by OsSalT suggested that modulation of such mannose-binding lectin could be a potential game-changer for the improvement of many crops in future.

From Soil Amendments to Controlling Autophagy: Supporting Plant Metabolism under Conditions of Water Shortage and Salinity

Crop resistance to environmental stress is a major issue. The globally increasing land degradation and desertification enhance the demand on management practices to balance both food and environmental objectives, including strategies that tighten nutrient cycles and maintain yields. Agriculture needs to provide, among other things, future additional ecosystem services, such as water quantity and quality, runoff control, soil fertility maintenance, carbon storage, climate regulation, and biodiversity. Numerous research projects have focused on the food–soil–climate nexus, and results were summarized in several reviews during the last decades. Based on this impressive piece of information, we have selected only a few aspects with the intention of studying plant–soil interactions and methods for optimization. In the short term, the use of soil amendments is currently attracting great interest to cover the current demand in agriculture. We will discuss the impact of biochar at water shortage, and plant growth promoting bacteria (PGPB) at improving nutrient supply to plants. In this review, our focus is on the interplay of both soil amendments on primary reactions of photosynthesis, plant growth conditions, and signaling during adaptation to environmental stress. Moreover, we aim at providing a general overview of how dehydration and salinity affect signaling in cells. With the use of the example of abscisic acid (ABA) and ethylene, we discuss the effects that can be observed when biochar and PGPB are used in the presence of stress. The stress response of plants is a multifactorial trait. Nevertheless, we will show that plants follow a general concept to adapt to unfavorable environmental conditions in the short and long term. However, plant species differ in the upper and lower regulatory limits of gene expression. Therefore, the presented data may help in the identification of traits for future breeding of stress-resistant crops. One target for breeding could be the removal and efficient recycling of damaged as well as needless compounds and structures. Furthermore, in this context, we will show that autophagy can be a useful goal of breeding measures, since the recycling of building blocks helps the cells to overcome a period of imbalanced substrate supply during stress adjustment.