Reactive Oxygen Species and Abiotic Stress in Plants

Meta-analysis of SnRK2 gene overexpression in response to drought and salt stress

SNF1-RELATED KINASE 2 (SnRK2) plays a crucial role in plants' stress response. Although studies have reported that the overexpression of several SnRK2 family members in different plants leads to improved stress tolerance, it is difficult to elucidate the mechanisms by which SnRK2s regulate stress tolerance due to the variability of experimental variables in these studies. Therefore, we used meta-analysis to comprehensively analyze 22 parameters that can reflect drought tolerance and salinity tolerance in SnRK2s-transformed plants and to explore the effects that different experimental variables between studies have on the relevant plant parameters. The results showed that the overexpression of SnRK2s mainly improved plants' drought and salinity tolerance by reducing their osmotic stress and oxidative damage, improving photosynthesis and other biochemical and physiological processes. Out of the 22 physiological parameters, 17 and 19 were significantly affected by drought and salt stress, respectively, and 10 indicators were also significantly changed under non-stress conditions. Under salt stress, the cell membrane permeability among these parameters shows the most significant changes, increasing by 506.57% in SnRK2-overexpressing plants compared to wild type (WT). Therefore, although plants overexpressing SnRK2s respond positively to both drought and salt stress, they demonstrated greater tolerance to salt stress. In addition, among the detected regulatory variables, donor-acceptor type, promoter type, stress type, experimental medium, and duration all affected the extent of SnRK2s overexpression and affected the physiological characteristics of the transgenic plants. Also, different stress conditions (salt, drought stress) led to different degrees of transformation. These studies provide new research directions for studying crop stress tolerance and help to better explore the functions played by SnRK2s in external plant stresses.

Investigation of Drought Stress on Chickpea (Cicer arietinum L.) Genotypes Employing Various Physiological Enzymatic and Non-Enzymatic Biochemical Parameters

Drought stress is a universal crisis in sustaining the growth and production of major legumes, including the chickpea. Drought severely reduces the biomass of chickpea plants, with the effect on leaves appearing the most apparent. The aim of this study was to investigate, using various physiological and biochemical markers throughout the pod filling stage, how 78 desi chickpea genotypes tolerated drought stress. Most of the evaluated characteristics showed significant variations between control and drought treatments. The mean performance of most of the investigated parameters significantly decreased under moisture-stressed conditions. RWC, SWD, MSI, and CTD were investigated under terminal drought-stressed conditions. Except for saturated water deficit (SWD), all remaining characteristics declined with increasing stress. Genotypes SAGL152210, SAGL152252, SAGL152347, SAGL22-115, and JG11 were recognized as drought-tolerant based on physiological characteristics. Biochemical markers viz., protein content, total soluble sugar, lipid peroxidation, and proline content, had an impact on osmotic adjustment. Based on non-enzymatic biochemical traits, genotypes SAGL22-115, ICC4958, ICCV201108, ICCV201107, SAGL152252, and JG11 were identified for their capability to survive under drought-stressed conditions. H2O2 content, CAT, SOD, POD, APX, and DPPH were considered antioxidant agents. Genotypes SAGL152208, SAGL22-105, SAGL22-112, ICC201108, SAGL152278, SAGL152252, SAGL162371, SAGL162390, ICC 4958, and JG315 may be considered drought-tolerant based on antioxidant activities. These genotypes are believed to be better equipped with physio-biochemical mechanisms and antioxidant defense systems at the cellular level and can be used in breeding programs to breed drought-tolerant cultivar(s). They can also be screened in the future, allowing the line(s) that have remained consistent over time to be recognized and registered as drought-tolerant donors.

An Integrated Framework for Drought Stress in Plants

With global warming, drought stress is becoming increasingly severe, causing serious impacts on crop yield and quality. In order to survive under adverse conditions such as drought stress, plants have evolved a certain mechanism to cope. The tolerance to drought stress is mainly improved through the synergistic effect of regulatory pathways, such as transcription factors, phytohormone, stomatal movement, osmotic substances, sRNA, and antioxidant systems. This study summarizes the research progress on plant drought resistance, in order to provide a reference for improving plant drought resistance and cultivating drought-resistant varieties through genetic engineering technology.

Response of selenium pools to drought stress by regulating physio‑biochemical attributes and anatomical changes in Gentiana macrophylla

Selenium (Se), as a vital stress ameliorant, possesses a beneficial effect on mediating detrimental effects of environmental threats. However, the mechanisms of Se in mitigating the deleterious effects of drought are still poorly understood. Gentiana macrophylla Pall. is a well-known Chinese medicinal herb, and its root, as the main medicinal site, has significant therapeutic effects. The purpose of this experiment was to investigate the functions of Se on the seedling growth and physiobiochemical characteristics in G. macrophylla subjected to drought stress. The changes in microstructure and chloroplast ultrastructure of G. macrophylla leaves under drought exposure were characterized by scanning electron microscopy (SEM), scanning electron microscopes and energy dispersive X-Ray spectroscope (SEM-EDX), and transmission electron microscopy (TEM), respectively. Results revealed that drought stress induced a notable increase in oxidative toxicity in G. macrophylla, as evidenced by elevated levels of hydrogen peroxide (H2O2), lipid peroxidation (MDA), enhanced antioxidative response, decreased plant photosynthetic function, and inhibited plant growth. Chloroplasts integrity with damaged membranes and excess osmiophilic granule were observed in the drought-stressed plants. Se supplementation notably recovered the stomatal morphology, anatomical structure damage, and chloroplast ultrastructure of G. macrophylla leaves caused by drought exposure. Exogenous Se application markedly enhanced SPAD, photosynthetic stomatal exchange parameters, and photosystem II activity. Se supplementation significantly promoted the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), while reducing levels of MDA, superoxide anion (O2-.) and H2O2, and improving membrane integrity. Furthermore, the ameliorative effects of Se were also suggested by increased contents of osmotic substances (soluble sugar and proline), boosted content of gentiopicroside and loganinic acid in roots, and alleviated the inhibition in plant growth and biomass. Fourier transform infrared (FTIR) analysis of Se-treated G. macrophylla roots under drought stress demonstrated that Se-stimulated metabolites including O-H, C-H, N-H, C-N, and CO functional groups, were involved in resisting drought stress. Correlation analysis indicated an obvious negative correlation between growth parameters and MDA, O2-. and H2O2 content, while a positive correlation with photosynthetic gas exchange parameters. Principal component analysis (PCA) results explained the total variance into two principal components contributing the maximum (93.50 %) among the drought exposure with or without Se due to the various experiment indexes. In conclusion, Se exerts beneficial properties on drought-induced detrimental effects in G. macrophylla by relieving oxidative stress, improving photosynthesis indexes, PSII activity, regulating anatomical changes, altering levels of gentiopicroside and loganinic acid, and promoting growth of drought-stressed G. macrophylla.

The genetic orchestra of salicylic acid in plant resilience to climate change induced abiotic stress: critical review

Climate change, driven by human activities and natural processes, has led to critical alterations in varying patterns during cropping seasons and is a vital threat to global food security. The climate change impose several abiotic stresses on crop production systems. These abiotic stresses include extreme temperatures, drought, and salinity, which expose agricultural fields to more vulnerable conditions and lead to substantial crop yield and quality losses. Plant hormones, especially salicylic acid (SA), has crucial roles for plant resiliency under unfavorable environments. This review explores the genetics and molecular mechanisms underlying SA's role in mitigating abiotic stress-induced damage in plants. It also explores the SA biosynthesis pathways, and highlights the regulation of their products under several abiotic stresses. Various roles and possible modes of action of SA in mitigating abiotic stresses are discussed, along with unraveling the genetic mechanisms and genes involved in responses under stress conditions. Additionally, this review investigates molecular pathways and mechanisms through which SA exerts its protective effects, such as redox signaling, cross-talks with other plant hormones, and mitogen-activated protein kinase pathways. Moreover, the review discusses potentials of using genetic engineering approaches, such as CRISPR technology, for deciphering the roles of SA in enhancing plant resilience to climate change related abiotic stresses. This comprehensive analysis bridges the gap between genetics of SA role in response to climate change related stressors. Overall goal is to highlight SA's significance in safeguarding plants and by offering insights of SA hormone for sustainable agriculture under challenging environmental conditions.

Biosynthetic selenium nanoparticles (Bio-SeNPs) mitigate the toxicity of antimony (Sb) in rice (Oryza sativa L.) by limiting Sb uptake, improving antioxidant defense system and regulating stress-related gene expression

Nanotechnology offers a promising and innovative approach to mitigate biotic and abiotic stress in crop production. In this study, the beneficial role and potential detoxification mechanism of biogenic selenium nanoparticles (Bio-SeNPs) prepared from Psidium guajava extracts in alleviating antimony (Sb) toxicity in rice seedlings (Oryza sativa L.) were investigated. The results revealed that exogenous addition of Bio-SeNPs (0.05 g/L) into the hydroponic-cultured system led to a substantial enhancement in rice shoot height (73.3%), shoot fresh weight (38.7%) and dry weight (28.8%) under 50 μM Sb(III) stress conditions. Compared to Sb exposure alone, hydroponic application of Bio-SeNPs also greatly promoted rice photosynthesis, improved cell viability and membrane integrity, reduced reactive oxygen species (ROS) levels, and increased antioxidant activities. Meanwhile, exogenous Bio-SeNPs application significantly lowered the Sb accumulation in rice roots (77.1%) and shoots (35.1%), and reduced its root to shoot translocation (55.3%). Additionally, Bio-SeNPs addition were found to modulate the subcellular distribution of Sb and the expression of genes associated with Sb detoxification in rice, such as OsCuZnSOD2, OsCATA, OsGSH1, OsABCC1, and OsWAK11. Overall, our findings highlight the great potential of Bio-SeNPs as a promising alternative for reducing Sb accumulation in crop plants and boosting crop production under Sb stress conditions.

The role of an Sb-oxidizing bacterium in modulating antimony speciation and iron plaque formation to reduce the accumulation and toxicity of Sb in rice (Oryza sativa L.)

Microbial antimony (Sb) oxidation in the root rhizosphere and the formation of iron plaque (IP) on the root surface are considered as two separate strategies to mitigate Sb(III) phytotoxicity. Here, the effect of an Sb-oxidizing bacterium Bacillus sp. S3 on IP characteristics of rice exposed to Sb(III) and its alleviating effects on plant growth were investigated. The results revealed that Fe(II) supply promoted IP formation under Sb(III) stress. However, the formed IP facilitated rather than hindered the uptake of Sb by rice roots. In contrast, the combined application of Fe(II) and Bacillus sp. S3 effectively alleviated Sb(III) toxicity in rice, resulting in improved rice growth and photosynthesis, reduced oxidative stress levels, enhanced antioxidant systems, and restricted Sb uptake and translocation. Despite the ability of Bacillus sp. S3 to oxidize Fe(II), bacterial inoculation inhibited the formation of IP, resulting in a reduction in Sb absorption on IP and uptake into the roots. Additionally, the bacterial inoculum enhanced the transformation of Sb(III) to less toxic Sb(V) in the culture solution, further influencing the adsorption of Sb onto IP. These findings highlight the potential of combining microbial Sb oxidation and IP as an effective strategy for minimizing Sb toxicity in sustainable rice production systems.

Reactive oxygen species signaling in melatonin-mediated plant stress response

Reactive oxygen species (ROS) are crucial signaling molecules in plants that play multifarious roles in prompt response to environmental stimuli. Despite the classical thoughts that ROS are toxic when accumulate in excess, recent advances in plant ROS signaling biology reveal that ROS participate in biotic and abiotic stress perception, signal integration, and stress-response network activation, hence contributing to plant defense and stress tolerance. ROS production, scavenging and transport are fine-tuned by plant hormones and stress-response signaling pathways. Crucially, the emerging plant hormone melatonin attenuates excessive ROS accumulation under stress, whereas ROS signaling mediates melatonin-induced plant developmental response and stress tolerance. In particular, RESPIRATORY BURST OXIDASE HOMOLOG (RBOH) proteins responsible for apoplastic ROS generation act downstream of melatonin to mediate stress response. In this review, we discuss promising developments in plant ROS signaling and how ROS might mediate melatonin-induced plant resilience to environmental stress.

Functional analysis of a rice 12-oxo-phytodienoic acid reductase gene (OsOPR1) involved in Cd stress tolerance

BACKGROUND

The accumulation of cadmium (Cd) in plants may compromise the growth and development of plants, thereby endangering human health through the food chain. Understanding how plants respond to Cd is important for breeding low-Cd rice cultivars.

METHODS

In this study, the functions of 12-oxo-phytodienoic acid reductase 1 (OsOPR1) were predicted through bioinformatics analysis. The expression levels of OsOPR1 under Cd stress were analyzed by using qRT-PCR. Then, the role that OsOPR1 gene plays in Cd tolerance was studied in Cd-sensitive yeast strain (ycf1), and the Cd concentration of transgenic yeast was analyzed using inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Bioinformatics analysis revealed that OsOPR1 was a protein with an Old yellow enzyme-like FMN (OYE_like_FMN) domain, and the cis-acting elements which regulate hormone synthesis or responding abiotic stress were abundant in the promoter region, which suggested that OsOPR1 may exhibit multifaceted biological functions. The expression pattern analysis showed that the expression levels of OsOPR1 were induced by Cd stress both in roots and roots of rice plants. However, the induced expression of OsOPR1 by Cd was more significant in the roots compared to that in roots. In addition, the overexpression of OsOPR1 improved the Cd tolerance of yeast cells by affecting the expression of antioxidant enzyme related genes and reducing Cd content in yeast cells.

CONCLUSION

Overall, these results suggested that OsOPR1 is a Cd-responsive gene and may has a potential for breeding low-Cd or Cd-tolerant rice cultivars and for phytoremediation of Cd-contaminated in farmland.

The apple autophagy-related gene MdATG10 improves drought tolerance and water use efficiency in transgenic apple plants

The Loess Plateau is the main apple production area in China; low precipitation is one of the most important factors limiting apple production here. Autophagy is a conserved process in eukaryotes that recycles cell contents or damaged macromolecules. Previously, we identified an autophagy-related gene MdATG10 from apple plants, which was involved in the responses to stressed conditions. In this study, we found that MdATG10 improved the drought tolerance and water use efficiency (WUE) of transgenic apple plants. MdATG10-overexpressing (OE) apple plants were more tolerant of short-term drought stress, as evidenced by their fewer drought-related injuries, compared with wild-type (WT) apple plants. In addition, the WUE of OE plants was higher than that of WT plants under long-term moderate water deficit conditions. The growth rate, biomass accumulation, photosynthetic efficiency, and stomatal aperture were higher in OE plants than in WT plants under long-term moderate drought conditions. During the process of adapting to drought, the expressions of genes involved in the abscisic acid (ABA) pathway were reduced in OE plants to decrease the synthesis of ABA, which helped maintain the stomatal opening for gas exchange. Furthermore, autophagic activity was higher in OE plants than in WT plants, as evidenced by the higher expressions of ATG genes and the greater number of autophagy bodies. In sum, our results suggested that overexpression of MdATG10 improved drought tolerance and WUE in apple plants, possibly by regulating stomatal movement and enhancing autophagic activity, which then enhanced the photosynthetic efficiency and reduced damage, as well as the reactive oxygen species (ROS) accumulation in apple plants.

Brevundimonas vesicularis (S1T13) Mitigates Drought-Stress-Associated Damage in Arabidopsis thaliana

Drought stress is a significant threat to agricultural productivity and poses challenges to plant survival and growth. Research into microbial plant biostimulants faces difficulties in understanding complicated ecological dynamics, molecular mechanisms, and specificity; to address these knowledge gaps, collaborative efforts and innovative strategies are needed. In the present study, we investigated the potential role of Brevundimonas vesicularis (S1T13) as a microbial plant biostimulant to enhance drought tolerance in Arabidopsis thaliana. We assessed the impact of S1T13 on Col-0 wild-type (WT) and atnced3 mutant plants under drought conditions. Our results revealed that the inoculation of S1T13 significantly contributed to plant vigor, with notable improvements observed in both genotypes. To elucidate the underlying mechanisms, we studied the role of ROS and their regulation by antioxidant genes and enzymes in plants inoculated with S1T13. Interestingly, the inoculation of S1T13 enhanced the activities of GSH, SOD, POD, and PPO by 33, 35, 41, and 44% in WT and 24, 22, 26, and 33% in atnced3, respectively. In addition, S1T13 upregulated the expression of antioxidant genes. This enhanced antioxidant machinery played a crucial role in neutralizing ROS and protecting plant cells from oxidative damage during drought stress. Furthermore, we investigated the impact of S1T13 on ABA and drought-stress-responsive genes. Similarly, S1T13 modulated the production of ABA and expression of AO3, ABA3, DREB1A, and DREB2A by 31, 42, 37, 41, and 42% in WT and 20, 29, 27, 38, and 29% in atnced3. The improvement in plant vigor, coupled with the induction of the antioxidant system and modulation of ABA, indicates the pivotal role of S1T13 in enhancing the drought stress tolerance of the plants. Conclusively, the current study provides valuable insights for the application of multitrait S1T13 as a novel strain to improve drought stress tolerance in plants and could be added to the consortium of biofertilizers.

Current Scenario and Future Prospects of Endophytic Microbes: Promising Candidates for Abiotic and Biotic Stress Management for Agricultural and Environmental Sustainability

Globally, substantial research into endophytic microbes is being conducted to increase agricultural and environmental sustainability. Endophytic microbes such as bacteria, actinomycetes, and fungi inhabit ubiquitously within the tissues of all plant species without causing any harm or disease. Endophytes form symbiotic relationships with diverse plant species and can regulate numerous host functions, including resistance to abiotic and biotic stresses, growth and development, and stimulating immune systems. Moreover, plant endophytes play a dominant role in nutrient cycling, biodegradation, and bioremediation, and are widely used in many industries. Endophytes have a stronger predisposition for enhancing mineral and metal solubility by cells through the secretion of organic acids with low molecular weight and metal-specific ligands (such as siderophores) that alter soil pH and boost binding activity. Finally, endophytes synthesize various bioactive compounds with high competence that are promising candidates for new drugs, antibiotics, and medicines. Bioprospecting of endophytic novel secondary metabolites has given momentum to sustainable agriculture for combating environmental stresses. Biotechnological interventions with the aid of endophytes played a pivotal role in crop improvement to mitigate biotic and abiotic stress conditions like drought, salinity, xenobiotic compounds, and heavy metals. Identification of putative genes from endophytes conferring resistance and tolerance to crop diseases, apart from those involved in the accumulation and degradation of contaminants, could open new avenues in agricultural research and development. Furthermore, a detailed molecular and biochemical understanding of endophyte entry and colonization strategy in the host would better help in manipulating crop productivity under changing climatic conditions. Therefore, the present review highlights current research trends based on the SCOPUS database, potential biotechnological interventions of endophytic microorganisms in combating environmental stresses influencing crop productivity, future opportunities of endophytes in improving plant stress tolerance, and their contribution to sustainable remediation of hazardous environmental contaminants.

Flavonoid metabolites in tea plant (Camellia sinensis) stress response: Insights from bibliometric analysis

In the context of global climate change, tea plants are at risk from elevating environmental stress factors. Coping with this problem relies upon the understanding of tea plant stress response and its underlying mechanisms. Over the past two decades, research in this field has prospered with the contributions of scientists worldwide. Aiming in providing a comprehensive perspective of the research field related to tea plant stress response, we present a bibliometric analysis of the this area. Our results demonstrate the most studied stresses, global contribution, authorship and collaboration, and trending research topics. We highlight the importance of flavonoid metabolites in tea plant stress response, particularly their role in maintaining redox homeostasis, yield, and adjusting tea quality under stress conditions. Further research on the flavonoid response under various stress conditions can promote the development of cultivation measures, thereby improving stress resistance and tea quality.

ROS and Abiotic Stress in Plants 2.0

Climate insecurity and extreme weather events have stimulated efforts to enhance plant resilience and productivity in adverse environmental conditions [...].

Selenium in soil-plant system: Transport, detoxification and bioremediation

Selenium (Se) is an essential micronutrient for humans and a beneficial element for plants. However, high Se doses always exhibit hazardous effects. Recently, Se toxicity in plant-soil system has received increasing attention. This review will summarize (1) Se concentration in soils and its sources, (2) Se bioavailability in soils and influencing factors, (3) mechanisms on Se uptake and translocation in plants, (4) toxicity and detoxification of Se in plants and (5) strategies to remediate Se pollution. High Se concentration mainly results from wastewater discharge and industrial waste dumping. Selenate (Se [VI]) and selenite (Se [IV]) are the two primary forms absorbed by plants. Soil conditions such as pH, redox potential, organic matter and microorganisms will influence Se bioavailability. In plants, excessive Se will interfere with element uptake, depress photosynthetic pigment biosynthesis, generate oxidative damages and cause genotoxicity. Plants employ a series of strategies to detoxify Se, such as activating antioxidant defense systems and sequestrating excessive Se in the vacuole. In order to alleviate Se toxicity to plants, some strategies can be applied, including phytoremediation, OM remediation, microbial remediation, adsorption technique, chemical reduction technology and exogenous substances (such as Methyl jasmonate, Nitric oxide and Melatonin). This review is expected to expand the knowledge of Se toxicity/detoxicity in soil-plant system and offer valuable insights into soils Se pollution remediation strategies.

Exogenous Calcium Induces Different Hydraulic Strategies in Response to Osmotic Stress in Maize Seedlings

Recent discoveries regarding the signal molecules involved in abiotic stresses require integration into the field of plant hydraulic property research. Although calcium (Ca) is an important second messenger involved in numerous complex, abiotic stress-induced signaling pathways, it remains unclear how exogenous calcium mediates cellular signaling to promote plant drought resistance. We investigated the effects of calcium on the water balance and hydraulic properties in maize seedlings (Zea mays L.) under osmotic stress simulated by 10% (m/v) PEG-6000 in a hydroponic culture. The osmotic stress dramatically decreased the photosynthetic rate, transpiration rate, stomatal conductance, leaf water content, and root water absorption. However, the short-term (2 h) and long-term (10 d) exogenous Ca2+ (CaCl2: 10 mM) treatments had different effects on the maize gas exchange parameters and leaf water status. The short-term treatment improved the leaf transpiration by inhibiting the abscisic acid (ABA) synthesis and accumulation in the leaves, generating a stronger transpiration pull and enhancing the root water absorption and axial flow path water transport by increasing the root hydraulic conductance to relieve the osmotic stress-induced inhibition. The long-term treatment induced the ABA and H2O2 accumulation in the roots and leaves. Under osmotic stress, the accumulation of ABA, H2O2, and Ca2+ rapidly repressed the transpiration and enhanced the radial flow path water transport, decreasing the water loss and improving the stress tolerance. These insights suggest a role for a judicious use of Ca fertilizer in reducing the adverse effects of drought on agricultural production.

Comprehensive analysis of HSF genes from celery (Apium graveolens L.) and functional characterization of AgHSFa6-1 in response to heat stress

High temperature stress is regarded as one of the significant abiotic stresses affecting the composition and distribution of natural habitats and the productivity of agriculturally significant plants worldwide. The HSF family is one of the most important transcription factors (TFs) families in plants and capable of responding rapidly to heat and other abiotic stresses. In this study, 29 AgHSFs were identified in celery and classified into three classes (A, B, and C) and 14 subgroups. The gene structures of AgHSFs in same subgroups were conserved, whereas in different classes were varied. AgHSF proteins were predicted to be involved in multiple biological processes by interacting with other proteins. Expression analysis revealed that AgHSF genes play a significant role in response to heat stress. Subsequently, AgHSFa6-1, which was significantly induced by high temperature, was selected for functional validation. AgHSFa6-1 was identified as a nuclear protein, and can upregulate the expression of certain downstream genes (HSP98.7, HSP70-1, BOB1, CPN60B, ADH2, APX1, GOLS1) in response to high-temperature treatment. Overexpression of AgHSFa6-1 in yeast and Arabidopsis displayed higher thermotolerance, both morphologically and physiologically. In response to heat stress, the transgenic plants produced considerably more proline, solute protein, antioxidant enzymes, and less MDA than wild-type (WT) plants. Overall, this study revealed that AgHSF family members perform a key role in response to high temperature, and AgHSFa6-1 acts as a positive regulator by augmenting the ROS-scavenging system to maintain membrane integrity, reducing stomatal apertures to control water loss, and upregulating the expression level of heat-stress sensitive genes to improve celery thermotolerance.

Melatonin and Abiotic Stress Tolerance in Crop Plants

Increasing food demand by the growing human population and declining crop productivity due to climate change affect global food security. To meet the challenges, developing improved crops that can tolerate abiotic stresses is a priority. Melatonin in plants, also known as phytomelatonin, is an active component of the various cellular mechanisms that alleviates oxidative damage in plants, hence supporting the plant to survive abiotic stress conditions. Exogenous melatonin strengthens this defence mechanism by enhancing the detoxification of reactive by-products, promoting physiological activities, and upregulating stress-responsive genes to alleviate damage during abiotic stress. In addition to its well-known antioxidant activity, melatonin protects against abiotic stress by regulating plant hormones, activating ER stress-responsive genes, and increasing protein homoeostasis, heat shock transcription factors and heat shock proteins. Under abiotic stress, melatonin enhances the unfolded protein response, endoplasmic reticulum-associated protein degradation, and autophagy, which ultimately protect cells from programmed cell death and promotes cell repair resulting in increased plant survival.

The transcription factor GhWRKY70 from gossypium hirsutum enhances resistance to verticillium wilt via the jasmonic acid pathway

BACKGROUND

The WRKY transcription factors play significant roles in plant growth, development, and defense responses. However, in cotton, the molecular mechanism of most WRKY proteins and their involvement in Verticillium wilt tolerance are not well understood.

RESULTS

GhWRKY70 is greatly up-regulated in cotton by Verticillium dahliae. Subcellular localization suggests that GhWRKY70 is only located in the nucleus. Transcriptional activation of GhWRKY70 further demonstrates that GhWRKY70 function as a transcriptional activator. Transgenic Arabidopsis plants overexpressing GhWRKY70 exhibited better growth performance and higher lignin content, antioxidant enzyme activities and jasmonic acid (JA) levels than wild-type plants after infection with V. dahliae. In addition, the transgenic Arabidopsis resulted in an enhanced expression level of AtAOS1, a gene related to JA synthesis, further leading to a higher JA accumulation compared to the wild type. However, the disease index (DI) values of the VIGS-treated cotton plants with TRV:WRKY70 were also significantly higher than those of the VIGS-treated cotton plants with TRV:00. The chlorophyll and lignin contents of TRV:WRKY70 plants were significantly lower than those of TRV:00 plants. GhAOS1 expression and JA abundance in TRV:WRKY70 plants were decreased. The GhWRKY70 protein was confirmed to bind to the W-box element in the promoter region of GhAOS by yeast one-hybrid assay and transient expression.

CONCLUSION

These results indicate that the GhWRKY70 transcription factor is a positive regulator in Verticillium wilt tolerance of cotton, and may promote the production of JA via regulation of GhAOS1 expression.

Chitosan-Enclosed Menadione Sodium Bisulfite as an Environmentally Friendly Alternative to Enhance Biostimulant Properties against Drought

Biostimulants are an interesting strategy to increase crop tolerance to water deficits, and there is an extensive bibliography on them. However, most of them need to be treated continuously to increase protection throughout the growth cycle. In this context, we chose menadione sodium bisulfite, whose protective effect against water deficit has been previously demonstrated but only for a short period of time. Nanoencapsulation seems to be an interesting way to improve the properties of biostimulants. Our results show that menadione sodium bisulfite (MSB) encapsulated in chitosan/tripolyphosphate nanoparticles can increase the system's tolerance against an imposed water deficit and delay the need for retreatment by at least 1 week, accelerating plant recovery after rehydration. This highlights the positive properties of nanoencapsulation and shows how a simple encapsulation process can significantly improve the biostimulant protective properties, opening up new possibilities to be explored under field conditions to cope with water-deficit stress.

Relationship between antioxidant enzymes and sclerotial formation of Pleurotus tuber-regium under abiotic stress

In order to explore the relationship between sclerotial formation and antioxidant enzymes under abiotic stresses, the effects of abiotic stresses including temperature, pH value, osmotic pressure, limited nitrogen, and hydrogen peroxide (H₂O₂) on the activities of antioxidant enzymes, ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in Pleurotus tuber-regium were studied. Meanwhile, the sclerotial formation under these abiotic stress conditions was also investigated. It was found that low temperature, weak alkaline, appropriate osmotic stress, and H₂O₂ can promote sclerotial formation, and sclerotial formation always tended to occur when the activities of antioxidant enzymes were at a high value. During the prolonged low temperature stress, SOD acted mainly in the early stage of stress, while POD and CAT had higher activity in the middle and late stage. Moreover, the reverse transcription quantitative polymerase chain reaction (RT-qPCR) results showed that SOD.193 and POD.535 were significantly down-regulated in sclerotia, and CAT.1115 and POD.401 were up-regulated instead. These antioxidant enzyme genes played an important role in the sclerotial formation under low temperature stress. It is strongly suggested that antioxidant enzymes and abiotic stresses are closely related to sclerotial formation in P. tuber-regium. KEY POINTS: • Low temperature and H2O2 can promote sclerotial formation. • Sclerotia are more likely to form under high antioxidant enzyme activity. • POD.401, POD.535, SOD.193, and CAT.1115 are important for sclerotial formation.

Comparative Transcriptomics Reveal Metabolic Rather than Genetic Control of Divergent Antioxidant Metabolism in the Primary Root Elongation Zone of Water-Stressed Cotton and Maize

Under water stress, the primary root elongation zones of cotton and maize exhibit both conserved and divergent metabolic responses, including variations in sulfur and antioxidant metabolism. To explore the relative importance of metabolic and genetic controls of these responses for each species, and the extent to which responses are mediated by similar gene expression networks within the framework of ortholog groups, comparative transcriptomics analyses were conducted under conditions of equivalent tissue water stress. Ortholog analysis revealed that 86% of the transcriptome response to water stress was phylogenetically unrelated between cotton and maize. Elevated transcript abundances for genes involved in abscisic acid (ABA) biosynthesis and signaling, as well as key enzymes that enable osmotic adjustment, were conserved between the species. In contrast, antioxidant responses, at least with regard to glutathione metabolism and anti-oxidative enzymes, did not exhibit such a transcript abundance adaptive signature. In particular, previously characterized differential responses of the glutathione and sulfur metabolic pathways between cotton and maize were not evident in the transcriptomic responses. The findings indicate that the antioxidant response in both species results from a metabolic acclimation to water stress, and thus represents an example of water stress-related metabolic plasticity.

The LEA gene family in tomato and its wild relatives: genome-wide identification, structural characterization, expression profiling, and role of SlLEA6 in drought stress

BACKGROUND

Late embryogenesis abundant (LEA) proteins are widely distributed in higher plants and play crucial roles in regulating plant growth and development processes and resisting abiotic stress. Cultivated tomato (Solanum lycopersicum) is an important vegetable crop worldwide; however, its growth, development, yield, and quality are currently severely constrained by abiotic stressors. In contrast, wild tomato species are more tolerant to abiotic stress and can grow normally in extreme environments. The main objective of this study was to identify, characterize, and perform gene expression analysis of LEA protein families from cultivated and wild tomato species to mine candidate genes and determine their potential role in abiotic stress tolerance in tomatoes.

RESULTS

Total 60, 69, 65, and 60 LEA genes were identified in S. lycopersicum, Solanum pimpinellifolium, Solanum pennellii, and Solanum lycopersicoides, respectively. Characterization results showed that these genes could be divided into eight clusters, with the LEA_2 cluster having the most members. Most LEA genes had few introns and were non-randomly distributed on chromosomes; the promoter regions contained numerous cis-acting regulatory elements related to abiotic stress tolerance and phytohormone responses. Evolutionary analysis showed that LEA genes were highly conserved and that the segmental duplication event played an important role in evolution of the LEA gene family. Transcription and expression pattern analyses revealed different regulatory patterns of LEA genes between cultivated and wild tomato species under normal conditions. Certain S. lycopersicum LEA (SlLEA) genes showed similar expression patterns and played specific roles under different abiotic stress and phytohormone treatments. Gene ontology and protein interaction analyses showed that most LEA genes acted in response to abiotic stimuli and water deficit. Five SlLEA proteins were found to interact with 11 S. lycopersicum WRKY proteins involved in development or resistance to stress. Virus-induced gene silencing of SlLEA6 affected the antioxidant and reactive oxygen species defense systems, increased the degree of cellular damage, and reduced drought resistance in S. lycopersicum.

CONCLUSION

These findings provide comprehensive information on LEA proteins in cultivated and wild tomato species and their possible functions under different abiotic and phytohormone stresses. The study systematically broadens our current understanding of LEA proteins and candidate genes and provides a theoretical basis for future functional studies aimed at improving stress resistance in tomato.

Selenium and molybdenum synergistically alleviate chromium toxicity by modulating Cr uptake and subcellular distribution in Nicotiana tabacum L

Chromium (Cr) is a harmful heavy metal that poses a serious threat to plants and animals. Selenium (Se) and molybdenum (Mo) are two beneficial elements for plant growth and resistance. However, their interactive effects on Cr uptake and distribution are poorly understood. Therefore, a hydroponics experiment was conducted to explore the effects of the use of Se and Mo alone and simultaneously on mitigating Cr toxicity. In this study, Nicotiana tabacum L. seedlings were exposed to control, 50 µM Cr, 50 μM Cr + 2 μM Se, 50 μM Cr + 1 μM Mo, or 50 μM Cr + 2 μM Se + 1 μM Mo in Hoagland solution. After 2 weeks, the plant biomass, Cr, Se and Mo contents, photosynthesis, leaf ultrastructure, antioxidant system, subcellular distribution and associated gene expression in Nicotiana tabacum L. were determined. The results showed that simultaneous use of Se and Mo promoted tobacco growth under Cr stress, as evidenced by reducing reactive oxygen species (ROS) content and reducing Cr translocation factor (TF) and inducing a 51.3% reduction in Cr content in shoots. Additionally, Se-Mo interactions increased the levels of glutathione (GSH) and phytochelatin (PC) and the distribution of Cr in the cell walls and organelles. Furthermore, the relative expression of PCS1 was upregulated, while those of NtST1 and MSN1 were downregulated. The results concluded that the simultaneous use of Se and Mo effectively alleviated Cr toxicity in Nicotiana tabacum L., which not only offers an efficient way for crops to resist Cr toxicity but also provides evidence for the benefit of Se combined with Mo.

Overexpression of CfICE1 from Cryptomeria fortunei Enhances Cold, Drought and Salt Stress in Poplar

ICE1, a regulator of the cold-inducible transcriptome and freezing tolerance, is currently widely believed to be involved in plant resistance to cold stress. In this study, CfICE1 from Cryptomeria fortunei was transformed into poplar. Physiological indicators of transgenic, empty vector and wild-type poplar after abiotic stress (cold, drought and salt) were determined. Transgenic lines had a higher chlorophyll content, antioxidant enzyme activity and soluble protein content, as well as a lower malondialdehyde and hydrogen peroxide content. The ultrastructure of the plant was observed by transmission electron microscopy, and after stress, the cell structure of the transgenic line was more complete than that of the wild type. CfICE1 was upregulated in transgenic poplar trees after abiotic stress (cold, drought and salt). The CfICE1 transgenic plants improved plant resistance by regulating the CBF gene of poplar under cold and salt stress. In terms of plant responses to abiotic stress, this study showed that overexpression of CfICE1 improved the cold, drought and salt tolerance of poplars.

ERF subfamily transcription factors and their function in plant responses to abiotic stresses

Ethylene Responsive Factor (ERF) subfamily comprise the largest number of proteins in the plant AP2/ERF superfamily, and have been most extensively studied on the biological functions. Members of this subfamily have been proven to regulate plant resistances to various abiotic stresses, such as drought, salinity, chilling and some other adversities. Under these stresses, ERFs are usually activated by mitogen-activated protein kinase induced phosphorylation or escape from ubiquitin-ligase enzymes, and then form complex with nucleic proteins before binding to cis-element in promoter regions of stress responsive genes. In this review, we will discuss the phylogenetic relationships among the ERF subfamily proteins, summarize molecular mechanism how the transcriptional activity of ERFs been regulated and how ERFs of different subgroup regulate the transcription of stress responsive genes, such as high-affinity K⁺ transporter gene PalHKT1;2, reactive oxygen species related genes LcLTP, LcPrx, and LcRP, flavonoids synthesis related genes FtF3H and LhMYBSPLATTER, etc. Though increasing researches demonstrate that ERFs are involved in various abiotic stresses, very few interact proteins and target genes of them have been comprehensively annotated. Hence, future research prospects are described on the mechanisms of how stress signals been transited to ERFs and how ERFs regulate the transcriptional expression of stress responsive genes.

Identification and Expression Profiling of Two Saudi Arabia Catalase Genes from Wheat and Barley in Response to Abiotic and Hormonal Stresses

Catalase is a crucial enzyme in antioxidant defense systems protecting eukaryotes from oxidative stress. These proteins are present in almost all living organisms and play important roles in controlling plant responses to biotic and abiotic stresses by catalyzing the decomposition of H₂O₂. Despite their importance, little is known about their expression in the majority of monocotyledonous species. Here, we isolated and characterized two novel catalase genes from Triticum turgidum and Hordeum vulgare, designated as TtCAT1 and HvCAT1, respectively. Phylogenetic analysis revealed that TtCAT1 and HvCAT1 presented 492 aa and shared an important identity with other catalase proteins belonging to subfamily 1. Using bioinformatic analysis, we predicted the 3D structure models of TtCAT1 and HvCAT1. Interestingly, analysis showed that the novel catalases harbor a peroxisomal targeting signal (PTS1) located at their C-terminus portion, as shown for other catalase proteins. In addition, this motif is responsible for the in silico peroxisomal localization of both proteins. Finally, RT-qPCR analysis showed that TtCAT1 and HvCAT1 are highly expressed in leaves in normal conditions but faintly in roots. Moreover, both genes are upregulated after the application of different stresses such as salt, osmotic, cold, heavy metal, and hormonal stresses. The positive responses of TtCAT1 and HvCAT1 to the various stimuli suggested that these proteins can help to protect both species against environmental stresses.

Versatile roles of polyamines in improving abiotic stress tolerance of plants

In recent years, extreme environmental cues such as abiotic stresses, including frequent droughts with irregular precipitation, salinity, metal contamination, and temperature fluctuations, have been escalating the damage to plants' optimal productivity worldwide. Therefore, yield maintenance under extreme events needs improvement in multiple mechanisms that can minimize the influence of abiotic stresses. Polyamines (PAs) are pivotally necessary for a defensive purpose under adverse abiotic conditions, but their molecular interplay in this remains speculative. The PAs' accretion is one of the most notable metabolic responses of plants under stress challenges. Recent studies reported the beneficial roles of PAs in plant development, including metabolic and physiological processes, unveiling their potential for inducing tolerance against adverse conditions. This review presents an overview of research about the most illustrious and remarkable achievements in strengthening plant tolerance to drought, salt, and temperature stresses by the exogenous application of PAs. The knowledge of underlying processes associated with stress tolerance and PA signaling pathways was also summarized, focusing on up-to-date evidence regarding the metabolic and physiological role of PAs with exogenous applications that protect plants under unfavorable climatic conditions. Conclusively, the literature proposes that PAs impart an imperative role in abiotic stress tolerance in plants. This implies potentially important feedback on PAs and plants' stress tolerance under unfavorable cues.

CqZF-HD14 enhances drought tolerance in quinoa seedlings through interaction with CqHIPP34 and CqNAC79

Drought stress is a key agricultural problem that restricts plant development and crop yield. Research on quinoa (Chenopodium quinoa), a nutrient-rich crop with strong stress resistance, has been limited in terms of the molecular regulation of its adaptation to drought stress. This study identified the zinc finger-homeodomain (ZF-HD) family in quinoa and a drought-responsive Chenopodium quinoa ZF-HD14 (CqZF-HD14) through expression profiles. Transient overexpression of CqZF-HD14 promotes photosynthetic pigment accumulation under drought stress, strengthens the antioxidant system, and in turn enhances drought tolerance. Comprehensive genome-wide family analysis and expression profiling identified CqNAC79 and CqHIPP34 regulated by CqZF-HD14, and their interactions were further determined by bimolecular fluorescence complementation (BIFC). Moreover, physiological and biochemical analyses and transient overexpression also revealed that CqNAC79 and CqHIPP34 resist drought by promoting the accumulation of photosynthetic pigments and maintaining antioxidant capacity under drought stress. The synergistic effect of CqZF-HD14 with CqNAC79 or CqHIPP34 further enhanced the drought tolerance of quinoa seedlings. Taken together, the results indicate that CqZF-HD14, CqNAC79 and CqHIPP34 may be important contributors to the drought tolerance regulatory network in quinoa, and these findings add new members to the drought tolerance gene pool.

Current Insights into the Molecular Mode of Action of Seaweed-Based Biostimulants and the Sustainability of Seaweeds as Raw Material Resources

Natural biostimulants, such as seaweed extracts, can stimulate plant growth and development in both model and crop plants. Due to the increasing demands for their use in agriculture, it is crucial to ensure the sustainability of the sources from which they are produced. Furthermore, some seaweed extracts were recently shown to prime and protect from adverse environmental factors such as drought, salinity and extreme temperatures, as well as from oxidative stress. The molecular mode of action of these biostimulants has still not been fully elucidated, but there has been significant progress in this direction in the last years. Firstly, this review examines the sustainability aspects of harvesting seaweed resources as raw materials for manufacturing biostimulants and provides an overview of the regulatory landscape pertaining to seaweed-based biostimulants. The review then summarises the recent advances in determining the genetic and molecular mechanisms activated by seaweed-based biostimulants, their influence on transcriptome reconfiguration, metabolite adjustment, and ultimately stress protection, improved nutrient uptake, and plant growth and performance. This knowledge is important for deciphering the intricate stress signalling network modulated by seaweed-based biostimulants and can aid in designing molecular priming technologies for crop improvement.

Modeling the Distribution of Wild Cotton Gossypium aridum in Mexico Using Flowering Growing Degree Days and Annual Available Soil Water

Climate change is expected to alter species distribution and habitat composition, with wild species being particularly vulnerable. Gossypium aridum, a wild cotton species in Mexico, has shown a decrease in habitat extent and population; however, the data are not precise. The objectives of this study are: (1) to develop a distribution model of G. aridum in Mexico, (2) to identify areas with environmental conditions similar to where the species currently maintains populations, and (3) to determine which variable, flowering growing degree days (FGDD) or annual available soil water (AASW, mm year−1), has greater influence on the distribution of the species. Geographic information system (GIS) software was used with datasets from two databases in Mexico that were partitioned for site characterization, model construction, calibration, validation, and sensitivity analysis. The range of 330–860 FGDD and 4–110 mm year−1 AASW best described the species habitat, according to results of seven precision and accuracy statistical tests. The model identified geographic regions throughout the country with similar conditions as the locations where the species has been observed, including some where no collections have not yet been registered in Mexican databases. FGDD, rather than AASW, showed greater influence on the distribution of the species. The generated information can be used to guide collection expeditions for G. aridum and to study climatic impact on species distribution. The approach using FGDD and AASW can be used in the modeling of wild cotton species that are valuable natural resources for crop improvement.

Zinc Oxide Nanoparticles Improve Pleioblastus pygmaeus Plant Tolerance to Arsenic and Mercury by Stimulating Antioxidant Defense and Reducing the Metal Accumulation and Translocation

The utilization of nanoparticles to potentially reduce toxicity from metals/metalloids in plants has increased in recent years, which can help them to achieve tolerance under the stressful conditions. An in vitro experiment was conducted to investigate five different levels of zinc oxide nanoparticles (ZnO-NPs; 0, 50, 100, 150, and 200 μM) both alone and in combination with 150 μM arsenic (As) and 150 μM mercury (Hg) in one-year-old Pleioblastus pygmaeus (Miq.) Nakai plants through four replications. The results demonstrated that As and Hg alone had damaging effects on the plant growth and development. However, the addition of various concentrations of ZnO-NPs led to increased antioxidant activity, proline (79%) content, glycine betaine (71%) content, tyrosine ammonia-lyase (43%) activity, phenylalanine ammonia-lyase (69%) activity, chlorophyll indices, and eventually plant biomass, while the lipoxygenase activity, electrolyte leakage, soluble protein, hydrogen peroxide content, and thiobarbituric acid reactive substances were reduced. We concluded that ZnO-NPs detoxified As and Hg toxicity in the plants through increasing antioxidant activity, reducing As and Hg accumulation, As and Hg translocation from roots to shoots, and adjusting stomatal closure. This detoxification was further confirmed by the reduction of the translocation factor of As and Hg and the enhancement of the tolerance index in combination with ZnO-NPs. However, there is a need for further investigation with different metals/metalloids.

How to Cope with the Challenges of Environmental Stresses in the Era of Global Climate Change: An Update on ROS Stave off in Plants

With the advent of human civilization and anthropogenic activities in the shade of urbanization and global climate change, plants are exposed to a complex set of abiotic stresses. These stresses affect plants’ growth, development, and yield and cause enormous crop losses worldwide. In this alarming scenario of global climate conditions, plants respond to such stresses through a highly balanced and finely tuned interaction between signaling molecules. The abiotic stresses initiate the quick release of reactive oxygen species (ROS) as toxic by-products of altered aerobic metabolism during different stress conditions at the cellular level. ROS includes both free oxygen radicals {superoxide (O₂^•−) and hydroxyl (OH⁻)} as well as non-radicals [hydrogen peroxide (H₂O₂) and singlet oxygen (¹O₂)]. ROS can be generated and scavenged in different cell organelles and cytoplasm depending on the type of stimulus. At high concentrations, ROS cause lipid peroxidation, DNA damage, protein oxidation, and necrosis, but at low to moderate concentrations, they play a crucial role as secondary messengers in intracellular signaling cascades. Because of their concentration-dependent dual role, a huge number of molecules tightly control the level of ROS in cells. The plants have evolved antioxidants and scavenging machinery equipped with different enzymes to maintain the equilibrium between the production and detoxification of ROS generated during stress. In this present article, we have focused on current insights on generation and scavenging of ROS during abiotic stresses. Moreover, the article will act as a knowledge base for new and pivotal studies on ROS generation and scavenging.

De novo and comparative transcriptomic analysis explain morphological differences in Panax notoginseng taproots

Background

Panax notoginseng (Burk.) F. H. Chen (PN) belonging to the genus Panax of family Araliaceae is widely used in traditional Chinese medicine to treat various diseases. PN taproot, as the most vital organ for the accumulation of bioactive components, presents a variable morphology (oval or long), even within the same environment. However, no related studies have yet explained the molecular mechanism of phenotypic differences. To investigate the cause of differences in the taproot phenotype, de novo and comparative transcriptomic analysis on PN taproot was performed.

Results

A total of 133,730,886 and 114,761,595 paired-end clean reads were obtained based on high-throughput sequencing from oval and long taproot samples, respectively. 121,955 unigenes with contig N50 = 1,774 bp were generated by using the de novo assembly transcriptome, 63,133 annotations were obtained with the BLAST. And then, 42 genes belong to class III peroxidase (PRX) gene family, 8 genes belong to L-Ascorbate peroxidase (APX) gene family, and 55 genes belong to a series of mitogen-activated protein kinase (MAPK) gene family were identified based on integrated annotation results. Differentially expressed genes analysis indicated substantial up-regulation of PnAPX3 and PnPRX45, which are related to reactive oxygen species metabolism, and the PnMPK3 gene, which is related to cell proliferation and plant root development, in long taproots compared with that in oval taproots. Furthermore, the determination results of real-time quantitative PCR, enzyme activity, and H₂O₂ content verified transcriptomic analysis results.

Conclusion

These results collectively demonstrate that reactive oxygen species (ROS) metabolism and the PnMPK3 gene may play vital roles in regulating the taproot phenotype of PN. This study provides further insights into the genetic mechanisms of phenotypic differences in other species of the genus Panax.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08283-w.

Response of Transgenic Potato Plants Expressing Heterologous Genes of ∆9- or ∆12-Acyl-lipid Desaturases to Phytophthora infestans Infection

Late blight is one of the most economically important diseases affecting potato and causing a significant loss in yield. The development of transgenic potato plants with enhanced resistance to infection by Phytophthora infestans may represent a possible approach to solving this issue. A comparative study of the leaf response in control potato plants (S.tuberosum L. cultivar Skoroplodnyi), control transgenic plants expressing the reporter gene of thermostable lichenase (transgenic licBM3 line) and transgenic plants expressing cyanobacterial hybrid genes ∆9-acyl-lipid desaturase (transgenic desC lines) and ∆12-acyl-lipid desaturase (transgenic desA lines) to infection with P. infestans has been performed. The expression of desaturase genes in potato plants enhanced their tolerance to potato late blight agents as compared with the control. The lipid peroxidation level raised in the leaves of the control and transgenic desA plants on third day after inoculation with P. infestans zoospores and remained the same in the transgenic desC plants. The number of total phenolic compounds was increased as early as on the second day after infection in all studied variants and continued to remain the same, except for transgenic desC plants. Accumulation of flavonoids, the main components of the potato leaf phenolic complex, raised on the second day in all studied variants, remained unchanged on the third day in the control plants and decreased in most transgenic plants expressing desaturase genes. The results obtained in our study demonstrate that the expression of genes of Δ9- and Δ12-acyl-lipid desaturases in potato plants enhanced their resistance to P. infestans as compared with the control non-transgenic plants due to concomitant accumulation of phenolic compounds, including flavonoids, in the leaves. All these changes were more pronounced in transgenic desC plants, which indicates that the Δ9-acyllipid desaturase gene appears to be a potential inducer of the production of biological antioxidants in plant cells.

Explicating the cross-talks between nanoparticles, signaling pathways and nutrient homeostasis during environmental stresses and xenobiotic toxicity for sustainable cultivation of cereals

Precision farming using nanoparticles is a cutting-edge technology for safe cultivation of crop plants in marginal areas afflicted with environmental/climatic stresses like salinity, drought, extremes of temperature, ultraviolet B stress or polluted with xenobiotics like toxic heavy metals and fluoride. Major cereal crops like rice, wheat, maize, barley, sorghum and millets which provide the staple food for the entire global population are mainly glycophytes and are extremely susceptible to abiotic stress-induced oxidative injuries. Nanofertilization/exogenous spraying of beneficial nanoparticles alleviates the oxidative damages in cereals by altering the homeostasis of phytohormones like abscisic acid, gibberellins, cytokinins, auxins, salicylic acid, jasmonic acid and melatonin and by triggering the synthesis of gasotransmitter nitric oxide. Signaling cross-talks of nanoparticles with plant growth regulators enable activation of the defence machinery, comprising of antioxidants, thiol-rich compounds and glyoxalases and restrict xenobiotic mobilization by suppressing the expression of associated transporters. Accelerated nutrient uptake and grain biofortification under the influence of nanoparticles result in optimum crop productivity under sub-optimal conditions. However, over-dosing of even beneficial nanoparticles promotes severe phytotoxicity. Hence, the concentration of nanoparticles and mode of administering need to be thoroughly standardized before large-scale field applications, to ensure sustainable cereal cultivation with minimum ecological imbalance.

Comparison of selenite and selenate in alleviation of drought stress in Nicotiana tabacum L

Exogenous selenium (Se) improves the tolerance of plants to abiotic stress. However, the effects and mechanisms of different Se species on drought stress alleviation are poorly understood. This study aims to evaluate and compare the different effects and mechanisms of sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) on the growth, photosynthesis, antioxidant system, osmotic substances and stress-responsive gene expression of Nicotiana tabacum L. under drought stress. The results revealed that drought stress could significantly inhibit growth, whereas both Na2SeO4 and Na2SeO3 could significantly facilitate the growth of N. tabacum under drought stress. However, compared to Na2SeO3, Se application as Na2SeO4 induced a significant increase in the root tip number and number of bifurcations under drought stress. Furthermore, both Na2SeO4 and Na2SeO3 displayed higher levels of photosynthetic pigments, better photosynthesis, and higher concentrations of osmotic substances, antioxidant enzymes, and stress-responsive gene (NtCDPK2, NtP5CS, NtAREB and NtLEA5) expression than drought stress alone. However, the application of Na2SeO4 showed higher expression levels of the NtP5CS and NtAREB genes than Na2SeO3. Both Na2SeO4 and Na2SeO3 alleviated many of the deleterious effects of drought in leaves, which was achieved by reducing stress-induced lipid peroxidation (MDA) and H2O2 content by enhancing the activity of antioxidant enzymes, while Na2SeO4 application showed lower H2O2 and MDA content than Na2SeO3 application. Overall, the results confirm the positive effects of Se application, especially Na2SeO4 application, which is markedly superior to Na2SeO3 in the role of resistance towards abiotic stress in N. tabacum.

Psychrophilic Bacterial Phosphate-Biofertilizers: A Novel Extremophile for Sustainable Crop Production under Cold Environment

Abiotic stresses, including low-temperature environments, adversely affect the structure, composition, and physiological activities of soil microbiomes. Also, low temperatures disturb physiological and metabolic processes, leading to major crop losses worldwide. Extreme cold temperature habitats are, however, an interesting source of psychrophilic and psychrotolerant phosphate solubilizing bacteria (PSB) that can ameliorate the low-temperature conditions while maintaining their physiological activities. The production of antifreeze proteins and expression of stress-induced genes at low temperatures favors the survival of such organisms during cold stress. The ability to facilitate plant growth by supplying a major plant nutrient, phosphorus, in P-deficient soil is one of the novel functional properties of cold-tolerant PSB. By contrast, plants growing under stress conditions require cold-tolerant rhizosphere bacteria to enhance their performance. To this end, the use of psychrophilic PSB formulations has been found effective in yield optimization under temperature-stressed conditions. Most of the research has been done on microbial P biofertilizers impacting plant growth under normal cultivation practices but little attention has been paid to the plant growth-promoting activities of cold-tolerant PSB on crops growing in low-temperature environments. This scientific gap formed the basis of the present manuscript and explains the rationale for the introduction of cold-tolerant PSB in competitive agronomic practices, including the mechanism of solubilization/mineralization, release of biosensor active biomolecules, molecular engineering of PSB for increasing both P solubilizing/mineralizing efficiency, and host range. The impact of extreme cold on the physiological activities of plants and how plants overcome such stresses is discussed briefly. It is time to enlarge the prospects of psychrophilic/psychrotolerant phosphate biofertilizers and take advantage of their precious, fundamental, and economical but enormous plant growth augmenting potential to ameliorate stress and facilitate crop production to satisfy the food demands of frighteningly growing human populations. The production and application of cold-tolerant P-biofertilizers will recuperate sustainable agriculture in cold adaptive agrosystems.

Cold Tolerance during the Reproductive Phase in Chickpea (Cicer arietinum L.) Is Associated with Superior Cold Acclimation Ability Involving Antioxidants and Cryoprotective Solutes in Anthers and Ovules

Chickpea is sensitive to cold stress, especially at reproductive stage, resulting in flower and pod abortion that significantly reduces seed yield. In the present study, we evaluated (a) whether cold acclimation imparts reproductive cold tolerance in chickpea; (b) how genotypes with contrasting sensitivity respond to cold acclimation; and (c) the involvement of cryoprotective solutes and antioxidants in anthers and ovules in cold acclimation. Four chickpea genotypes with contrasting cold sensitivity (cold-tolerant: ICC 17258, ICC 16349; cold-sensitive: ICC 15567, GPF 2) were grown in an outdoor environment for 40 days in November (average maximum/minimum temperature 24.9/15.9 °C) before being subjected to cold stress (13/7 °C), with or without cold acclimation in a controlled environment of walk-in-growth chambers. The 42-d cold acclimation involved 7 d exposure at each temperature beginning with 23/15 °C, 21/13 °C, 20/12 °C, 20/10 °C, 18/8 °C, 15/8 °C (12 h/12 h day/night), prior to exposing the plants to cold stress (13/7 °C, 12 h/12 h day/night; 700 μmol m⁻² s⁻¹ light intensity; 65–70% relative humidity). Cold acclimation remarkably reduced low temperature-induced leaf damage (as membrane integrity, leaf water status, stomatal conductance, photosynthetic pigments, and chlorophyll fluorescence) under cold stress in all four genotypes. It only reduced anther and ovule damage in cold-tolerant genotypes due to improved antioxidative ability, measured as enzymatic (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and non-enzymatic (ascorbate and reduced glutathione), solutes (particularly sucrose and γ-aminobutyric acid) leading to improving reproductive function and yield traits, whereas cold-sensitive genotypes were not responsive. The study concluded that cold tolerance in chickpea appears to be related to the better ability of anthers and ovules to acclimate, involving various antioxidants and cryoprotective solutes. This information will be useful in directing efforts toward increasing cold tolerance in chickpea.

Investigation of Distinctive Morpho-Physio and Biochemical Alterations in Desi Chickpea at Seedling Stage Under Irrigation, Heat, and Combined Stress

Global climatic instabilities have become the main reason for drastic yield losses in chickpea. This shift in climate could be a great threat in the future for food security in developing countries. Chickpea production is badly hampered by heat stress coupled with drought stress, and these factors can reduce yields by 40-45%. To mitigate yield losses due these abiotic factors, irrigation supplementation could be the best strategy. The present study aimed to (i) investigate the tolerance response of 9 desi chickpea genotypes against heat stress (H), irrigation (I), and a combination of both (I+H) through morphophysiological and biochemical indices at early growth stage, and (ii) assess yield performance across multiple locations of the country. Results revealed that under irrigation treatment, all genotypes perform well, but the genotypes D-09027 and D-09013 showed best performance because, as compared to control, they retained root length, seedling fresh weight, root fresh weight, root dry weight, esterase activity, Malondialdehyde (MDA) content, total chlorophyll, and total carotenoids. Shoot length and total phenolic contents (TPC) increased in both genotypes. Superoxide dismutase (SOD) and peroxidase (POD) increased in D-09027 and retained in D-09013. Catalase activity increased in D-09013 and retained in D-09027. Protease activity, total water potential and osmotic potential decreased in both genotypes and depicted high yield potential with 27 and 30% increase in yield over Bhakhar-2011 (check), respectively. In case of heat stress, maximum tolerance was found in genotypes CH104/06 and D-09013 with no change in shoot and root length, seedling dry weight, shoot fresh and dry weight, root dry weight, relative water content, turgor water potential, catalase (CAT) activity, esterase activity, increased root fresh weight, peroxidase activity (POD), ascorbate peroxidase activity (APX), and lycopene with low accumulation of protease and Malondialdehyde content (MDA). Both genotypes depicted high yield potential with 30 and 43% increase in yield over check across multiple locations of the country. Under the combined treatment, most genotypes showed good performance, while CH104/06 was selected as best performer genotype because significant of its increased root fresh weight, lycopene content, chlorophyll b, total carotenoids, total chlorophyll, retained shoot length, root length, seedling fresh and dry weight, total water potential, osmotic potential, relative water content, peroxidase activity (POD), catalase, esterase, and its ascorbate peroxidase (APX) activity and total soluble proteins (TSP) showed highest yield potential with 43% increase over check. Identified best performing and tolerant genotypes can further be employed for breeding climate-smart chickpea genotypes for sustainable production under changing climate.

Impact of Wheat Streak Mosaic Virus on Peroxisome Proliferation, Redox Reactions, and Resistance Responses in Wheat

Although peroxisomes play an essential role in viral pathogenesis, and viruses are known to change peroxisome morphology, the role of genotype in the peroxisomal response to viruses remains poorly understood. Here, we analyzed the impact of wheat streak mosaic virus (WSMV) on the peroxisome proliferation in the context of pathogen response, redox homeostasis, and yield in two wheat cultivars, Patras and Pamir, in the field trials. We observed greater virus content and yield losses in Pamir than in Patras. Leaf chlorophyll and protein content measured at the beginning of flowering were also more sensitive to WSMV infection in Pamir. Patras responded to the WSMV infection by transcriptional up-regulation of the peroxisome fission genes PEROXIN 11C (PEX11C), DYNAMIN RELATED PROTEIN 5B (DRP5B), and FISSION1A (FIS1A), greater peroxisome abundance, and activation of pathogenesis-related proteins chitinase, and β-1,3-glucanase. Oppositely, in Pamir, WMSV infection suppressed transcription of peroxisome biogenesis genes and activity of chitinase and β-1,3-glucanase, and did not affect peroxisome abundance. Activity of ROS scavenging enzymes was higher in Patras than in Pamir. Thus, the impact of WMSV on peroxisome proliferation is genotype-specific and peroxisome abundance can be used as a proxy for the magnitude of plant immune response.

Multiple responses contribute to the enhanced drought tolerance of the autotetraploid Ziziphus jujuba Mill. var. spinosa

Background

Polyploid plants often exhibit enhanced stress tolerance. The underlying physiological and molecular bases of such mechanisms remain elusive. Here, we characterized the drought tolerance of autotetraploid sour jujube at phenotypic, physiological and molecular levels.

Results

The study findings showed that the autotetraploid sour jujube exhibited a superior drought tolerance and enhanced regrowth potential after dehydration in comparison with the diploid counterpart. Under drought stress, more differentially expressed genes (DEGs) were detected in autotetraploid sour jujube and the physiological responses gradually triggered important functions. Through GO enrichment analysis, many DEGs between the diploid and autotetraploid sour jujube after drought-stress exposure were annotated to the oxidation–reduction process, photosystem, DNA binding transcription factor activity and oxidoreductase activity. Six reactive oxygen species scavenging-related genes were specifically differentially expressed and the larger positive fold-changes of the DEGs involved in glutathione metabolism were detected in autotetraploid. Consistently, the lower O²⁻ level and malonaldehyde (MDA) content and higher antioxidant enzymes activity were detected in the autotetraploid under drought-stress conditions. In addition, DEGs in the autotetraploid after stress exposure were significantly enriched in anthocyanin biosynthesis, DNA replication, photosynthesis and plant hormone, including auxin, abscisic acid and gibberellin signal-transduction pathways. Under osmotic stress conditions, genes associated with the synthesis and transport of osmotic regulators including anthocyanin biosynthesis genes were differentially expressed, and the soluble sugar, soluble protein and proline contents were significantly higher in the autotetraploid. The higher chlorophyll content and DEGs enriched in photosynthesis suggest that the photosynthetic system in the autotetraploid was enhanced compared with diploid during drought stress. Moreover, several genes encoding transcription factors (TFs) including GRAS, Bhlh, MYB, WRKY and NAC were induced specifically or to higher levels in the autotetraploid under drought-stress conditions, and hub genes, LOC107403632, LOC107422279, LOC107434947, LOC107412673 and LOC107432609, related to 18 up-regulated transcription factors in the autotetraploid compared with the diploid were identified.

Conclusion

Taken together, multiple responses contribute to the enhanced drought tolerance of autotetraploid sour jujube. This study could provide an important basis for elucidating the mechanism of tolerance variation after the polyploidization of trees.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00633-1.

Effects of nitrogen fertilization and drought on hydrocyanic acid accumulation and morpho-physiological parameters of sorghums

BACKGROUND

Nitrogen fertilization can increase sorghum yield and quality and the hydrocyanic acid (HCN) accumulation in plants, increasing the risk of animal toxicity, particularly under drought conditions. In this study, plants of three sorghum genotypes (sweet sorghum, sudangrass and hybrid sorghum) were supplemented with nitrogen (0, 60, 90 and 120 kg N ha^-1 ) under well-watered and drought-stressed conditions, aiming to investigate the responses of morpho-physiological parameters and HCN accumulation to drought and nitrogen fertilization.

RESULTS

Drought caused a decline in growth and photosynthesis. Average HCN content increased by 27.85% in drought-stressed plants when compared with those in well-watered plants. Drought increased the proline and soluble protein content, the content of O₂ ^- , H₂ O₂ and malondialdehyde (MDA), and the activities of antioxidant enzymes in leaves of all three genotypes. Maximum plant growth and higher plant nutrient content (nitrogen and phosphorus) were observed at 120 kg N ha^-1 , followed by 90 and 60 kg N ha^-1 . However, a sharp increase in HCN content and a decrease in antioxidant enzyme activities were observed when nitrogen rates increased from 90 to 120 kg N ha^-1 , suggesting that 90 kg N ha^-1 might be better for sorghums under drought conditions.

CONCLUSION

These results suggest that optimum nitrogen application on sorghum under drought conditions could achieve a balance between plant defense and food safety, attributed to the reduced MDA, O₂ ^- and H₂ O₂ accumulation, the improvement in photosynthesis parameters, the increase in soluble protein and proline content, and the increase in antioxidant enzyme activities. © 2020 Society of Chemical Industry.

Aquaporins in Cereals-Important Players in Maintaining Cell Homeostasis under Abiotic Stress

Cereal productivity is reduced by environmental stresses such as drought, heat, elevated CO₂, salinity, metal toxicity and cold. Sometimes, plants are exposed to multiple stresses simultaneously. Plants must be able to make a rapid and adequate response to these environmental stimuli in order to restore their growing ability. The latest research has shown that aquaporins are important players in maintaining cell homeostasis under abiotic stress. Aquaporins are membrane intrinsic proteins (MIP) that form pores in the cellular membranes, which facilitate the movement of water and many other molecules such as ammonia, urea, CO₂, micronutrients (silicon and boron), glycerol and reactive oxygen species (hydrogen peroxide) across the cell and intercellular compartments. The present review primarily focuses on the diversity of aquaporins in cereal species, their cellular and subcellular localisation, their expression and their functioning under abiotic stresses. Lastly, this review discusses the potential use of mutants and plants that overexpress the aquaporin-encoding genes to improve their tolerance to abiotic stress.

Interactive effect of potassium and cadmium on growth, root morphology and chlorophyll a fluorescence in tomato plant

A hydroponic experiment was conducted to evaluate the role of potassium (K) in tomato plant growth exposed to cadmium (Cd) stress. In this work, the effects of three potassium nutrition regimes (155, 232 and 310 ppm of K) combined with Cd at different levels (0, 12 and 25 µM of CdCl₂) on chlorophyll content index, root and shoot dry weights, root morphology, chlorophyll a fluorescence and translocation factor were analyzed. The results showed a negative effect of cadmium, at different concentrations, on all these parameters. However, optimization of K nutrition has shown promising results by limiting the negative effect of Cd. A positive effect of the high concentration of K (310 ppm) was observed on leaf chlorophyll content and chlorophyll a fluorescence compared to 232 and 155 ppm under Cd stress. K supply improved the electron transport at PSI side indicated by the increase in the amplitude of the I-P phase of OJIP transient. Also, K at a concentration of 310 ppm significantly reduced Cd translocation from root to shoot and improved root and shoot growth parameters in the presence of Cd. K supplementation can reduce the negative effect of Cd by improving photosynthesis and promoting chlorophyll synthesis. The optimization of nutrients composition and concentration might be a good strategy to reduce the impact of Cd on plant growth and physiology.

Jasmonic Acid Impairs Arabidopsis Seedling Salt Stress Tolerance Through MYC2-Mediated Repression of CAT2 Expression

High salinity causes ionic, osmotic, and oxidative stresses to plants, and the antioxidant enzyme Catalase2 (CAT2) plays a vital role in this process, while how CAT2 expression is regulated during plant response to high salinity remains elusive. Here, we report that phytohormone jasmonic acid (JA) impairs plant salt stress tolerance by repressing CAT2 expression in an MYC2-dependent manner. Exogenous JA application decreased plant salt stress tolerance while the jar1 mutant with reduced bioactive JA-Ile accumulation showed enhanced salt stress tolerance. JA enhanced salt-induced hydrogen peroxide (H₂O₂) accumulation, while treatment with H₂O₂-scavenger glutathione compromised such effects of JA on plant H₂O₂ accumulation and salt stress tolerance. In addition, JA repressed CAT2 expression in salt-stressed wild-type plant but not in myc2, a mutant of the master transcriptional factor MYC2 in JA signaling, therefore, the myc2 mutant exhibited increased salt stress tolerance. Further study showed that mutation of CAT2 largely reverted lower reactive oxygen species (ROS) accumulation, higher CAT activity, and enhanced salt stress tolerance of the myc2 mutant in myc2 cat2-1 double mutant, revealing that CAT2 functions downstream JA-MYC2 module in plant response to high salinity. Together, our study reveals that JA impairs Arabidopsis seedling salt stress tolerance through MYC2-mediated repression of CAT2 expression.