Cis-elements and trans-factors that regulate expression of the maize Cat1 antioxidant gene in response to ABA and osmotic stress: H2O2 is the likely intermediary signaling molecule for the response

HvAIR12 confers aluminum tolerance in barley by H2O2-mediated activation of HvEXPA4 to facilitate aluminum detoxification and improve root growth

Aluminum (Al) toxicity is a major constraint on crop productivity in acid soils, with barley being particularly susceptible. In our previous transcriptomic analysis, we identified HvAIR12 (AUXIN INDUCED IN ROOT CULTURES), a novel gene that is specifically induced by Al in the roots of the Al-tolerant Tibetan wild barley accession XZ16. In this study, we performed comprehensive physiological, transgenic, and molecular analyses to explore the role of HvAIR12 in Al tolerance. HvAIR12 encodes a plasma membrane-bound protein and is predominantly expressed in the roots, with its expression being strongly upregulated by Al exposure. Knockdown of HvAIR12 resulted in significantly reduced root growth and increased Al accumulation, whereas overexpression of HvAIR12 elevated H2O2 levels in the apoplast and promoted root growth-effects that were reversible by H2O2 scavengers. RNA sequencing further revealed that overexpression of HvAIR12 led to the transcriptional activation of several expansin genes, including HvEXPA4 and HvEXPB2. Functional characterization of HvEXPA4 transgenic lines and gene silencing experiments in HvAIR12-overexpressing backgrounds confirmed that HvEXPA4 is an essential downstream target of HvAIR12, mitigating Al toxicity by modulating cell wall components. This study uncovers the novel role of HvAIR12 in regulating apoplastic H2O2 levels and its interaction with other Al tolerance-related genes. Our findings highlight that HvAIR12 promotes Al tolerance through H2O2-mediated activation of HvEXPA4, forming a regulatory pathway critical for Al exclusion and root elongation under Al stress. These results providing valuable molecular insights and promising target genes for breeding more resilient cereal crops for cultivation in acid soils.

Comparative transcriptome analysis provides insights into ABA alleviating postharvest physiological deterioration of cassava

Cassava, a staple crop in tropical regions, suffers from rapid postharvest physiological deterioration (PPD), limiting its shelf life. Although abscisic acid (ABA) has shown potential in alleviating PPD, the underlying regulatory pathways remain largely unexplored. In this study, physiological assays demonstrated that exogenous ABA alleviated PPD in cassava by decreasing H2O2 content. Temporal-resolution transcriptome analyses identified gene expression changes in cassava tuberous roots during PPD, with 1,338, 2,718, and 5543 genes differentially expressed after 6, 12, and 48 h of treatment, respectively. GO enrichment analysis revealed that ABA-induced DEGs exhibited functions such as response to oxygen radical, lignin metabolic process, and positive regulation of signal transduction. Co-expression network analysis identified three significant gene modules comprising 167 transcription factors (TFs) from 28 families, with 17 TFs predicted to regulate six key antioxidant enzyme genes through corresponding promoter motifs. The upregulated expression of these genes was subsequently validated by quantitative real-time PCR (qRT-PCR). Furthermore, yeast one-hybrid (Y1H) and dual-luciferase assays provided direct evidences that MeMYB114 and MeHAT22 regulate the expression of MePOD10, while MeERF110, MeWRKY057, and MeHAT22 were shown to activate MePOD18 expression. These findings indicate that MeMYB114/MeHAT22/MeERF110/MeWRKY057-MePOD pathway is a crucial component involved in ABA-regulated PPD alleviation in cassava.

Glycine betaine enhances tolerance of low temperature combined with low light in pepper (Capsicum annuum L.) by improving the antioxidant capacity and regulating GB metabolism

Glycine betaine (GB) is commonly used as an osmotic regulator and a donor to facilitate changes in methylation in plants and animals, thereby enhancing stress resistance. However, low temperature combined with low light stress represent the most prevalent stresses during pepper growth period in northwest China, and limited studies have focused on the potential stress-mitigating effects of GB. Therefore, to examine the regulatory mechanism of GB-induced tolerance to LL stress, pepper seedlings were pretreated with 20 mmol L-1 GB and 60 μmol L-1 3-Deazaneplanocin A hydrochloride at a temperature of 10/5 °C and illumination of 100 μmol m-2 s-1. The results demonstrated that GB significantly alleviated the detrimental effects of low temperature combined with low light stress on growth of primary and lateral roots and increased the roots absorption of mineral nutrients (N, P, Ca, Fe, and Zn). In addition, GB induced the expression of the genes for CaSOD, CaPOD, CaCAT, CaGR1, and CaDHAR, improved osmotic regulation, and increased the activities of enzymatic (superoxide dismutase, peroxidase, catalase, glutathione reductase, and dehydroascorbate reductase) and non-enzymatic antioxidants (ascorbate and glutathione). This resulted in enhanced scavenging of reactive oxygen species, thereby maintaining a balanced oxidation-reduction within the cells. Furthermore, GB substituted S-adenosylmethionine, a partial methylation donor, during the methyl group metabolism process, altering the m6A methylation level and increasing the resistance of pepper seedlings to LL stress. Overall, exogenous GB pretreatment could be used as a potential strategy for enhancing the LL tolerance of plants.

Investigating the Allelopathic and Bioherbicidal Potential of Solidago altissima with a Focus on Chemical Signaling in Trifolium repens

Invasive weed species exhibit both advantages, such as the potential for allelochemicals in bioherbicide development, and risks, including their threat to crop production. Therefore, this study aims to identify an allelochemical from Solidago altissima, an invasive weed species. The dose-dependent effects of S. altissima shoot and root extracts (SSE, SRE) on the signaling in the forage crop Trifolium repens and germination in various weed species (Echinochloa oryzicola, Cyperus microiria, Alopecurus aequalis, Portulaca oleracea, and Amaranthus retroflexus) were evaluated. The results showed that the T. repens seedlings treated with root extracts exhibited a significant decrease in plant height, dry weight, and chlorophyll content, along with an increase in H2O2 levels. Additionally, antioxidant activities, such as superoxide dismutase, catalase, and peroxidase enzyme activities, were significantly elevated in T. repens treated with SRE. Moreover, SRE treatment significantly inhibited the seed germination of all tested weed species in a concentration-dependent manner. Gas chromatography-mass spectrometry analysis of S. altissima root extract identified a high concentration of methyl kolavenate, a clerodane diterpene predicted to act as a phytotoxic agent. These findings highlight the potential of S. altissima for the development of crop-protective agents while emphasizing its potential risks in agriculture.

Differentially Expressed Genes Identification of Kohlrabi Seedlings (Brassica oleracea var. caulorapa L.) under Polyethylene Glycol Osmotic Stress and AP2/ERF Transcription Factor Family Analysis

Osmotic stress is a condition in which plants do not get enough water due to changes in environmental factors. Plant response to osmotic stress is a complex process involving the interaction of different stress-sensitive mechanisms. Differentially expressed genes and response mechanisms of kohlrabi have not been reported under osmotic stress. A total of 196,642 unigenes and 33,040 differentially expressed unigenes were identified in kohlrabi seedlings under polyethylene glycol osmotic stress. AP2/ERF, NAC and eight other transcription factor family members with a high degree of interaction with CAT and SOD antioxidant enzyme activity were identified. Subsequently, 151 AP2/ERF genes were identified and analyzed. Twelve conserved motifs were searched and all AP2/ERF genes were clustered into four groups. A total of 149 AP2/ERF genes were randomly distributed on the chromosome, and relative expression level analysis showed that BocAP2/ERF genes of kohlrabi have obvious specificity in different tissues. This study lays a foundation for explaining the osmotic stress resistance mechanism of kohlrabi and provides a theoretical basis for the functional analysis of BocAP2/ERF transcription factor family members.

MdPRX34L, a class III peroxidase gene, activates the immune response in apple to the fungal pathogen Botryosphaeria dothidea

MAIN CONCLUSION

MdPRX34L enhanced resistance to Botryosphaeria dothidea by increasing salicylic acid (SA) and abscisic acid (ABA) content as well as the expression of related defense genes. The class III peroxidase (PRX) multigene family is involved in complex biological processes. However, the molecular mechanism of PRXs in the pathogen defense of plants against Botryosphaeria dothidea (B. dothidea) remains unclear. Here, we cloned the PRX gene MdPRX34L, which was identified as a positive regulator of the defense response to B. dothidea, from the apple cultivar 'Royal Gala.' Overexpression of MdPRX34L in apple calli decreased sensitivity to salicylic acid (SA) and abscisic acid（ABA). Subsequently, overexpression of MdPRX34L in apple calli increased resistance to B. dothidea infection. In addition, SA contents and the expression levels of genes related to SA synthesis and signaling in apple calli overexpressing MdPRX34L were higher than those in the control after inoculation, suggesting that MdPRX34L enhances resistance to B. dothidea via the SA pathway. Interestingly, infections in apple calli by B. dothidea caused an increase in endogenous levels of ABA followed by induction of ABA-related genes expression. These findings suggest a potential mechanism by which MdPRX34L enhances plant-pathogen defense against B. dothidea by regulating the SA and ABA pathways.

Metabolic pathways modulated by coumarin to inhibit seed germination and early seedling growth in Eleusine indica

Coumarin is an allelochemical that is widely present in the plant kingdom and has great potential for weed control. However, its mechanisms of action remain largely unknown. This study employed metabolomic and transcriptomic analyses along with evaluations of amino acid profiles and related physiological indicators to investigate how coumarin inhibits the germination and seedling growth of Eleusine indica by modifying metabolic pathways. At 72 h of germination at 50 and 100 mg L-1 coumarin, E. indica had lower levels of soluble sugar and activities of amylases and higher levels of starch, O2-, H2O2, auxin (IAA) and abscisic acid (ABA) compared to the control. Metabolomic analysis demonstrated that coumarin treatments had a significant impact on the pathways associated with amino acid metabolism and transport and aminoacyl-tRNA biosynthesis. Exposure to coumarin induced significant alterations in the levels of 19 amino acids, with a decrease in 15 of them, including Met, Leu and γ-aminobutyric acid (GABA). Additionally, transcriptomic analysis showed that coumarin significantly disrupted several essential biological processes, including protein translation, secondary metabolite synthesis, and hormone signal transduction. The decrease in TCA cycle metabolite (cis-aconitate, 2-oxoglutarate, and malate) contents was associated with the suppression of transcription for related enzymes. Our findings indicate that the inhibition of germination and growth in E. indica by coumarin involves the suppression of starch conversion to sugars, modification of the amino acid profile, interference of hormone signalling and the induction of oxidative stress. The TCA cycle appears to be one of the most essential pathways affected by coumarin.

Screening and evaluation of drought resistance traits of winter wheat in the North China Plain

Background

Drought-resistant varieties are an important way to address the conflict between wheat's high water demand and the scarcity of water resources in the North China Plain (NCP). Drought stress impacts many morphological and physiological indicators in winter wheat. To increase the effectiveness of breeding drought-tolerant varieties, choosing indices that can accurately indicate a variety's drought resistance is advantageous.

Results

From 2019 to 2021, 16 representative winter wheat cultivars were cultivated in the field, and 24 traits, including morphological, photosynthetic, physiological, canopy, and yield component traits, were measured to evaluate the drought tolerance of the cultivars. Principal component analysis (PCA) was used to transform 24 conventional traits into 7 independent, comprehensive indices, and 10 drought tolerance indicators were screened out by regression analysis. The 10 drought tolerance indicators were plant height (PH), spike number (SN), spikelet per spike(SP), canopy temperature (CT), leaf water content (LWC), photosynthetic rate (A), intercellular CO2 concentration (Ci), peroxidase activity (POD), malondialdehyde content (MDA), and abscisic acid (ABA). In addition, through membership function and cluster analysis, 16 wheat varieties were divided into 3 categories: drought-resistant, drought weak sensitive, and drought-sensitive.

Conclusion

JM418, HM19,SM22, H4399, HG35, and GY2018 exhibited excellent drought tolerance and,therefore, can be used as ideal references to study the drought tolerance mechanism in wheat and breeding drought-tolerant wheat cultivars.

Novel flavin-containing monooxygenase protein FMO1 interacts with CAT2 to negatively regulate drought tolerance through ROS homeostasis and ABA signaling pathway in tomato

Drought stress is the major abiotic factor that can seriously affect plant growth and crop production. The functions of flavin-containing monooxygenases (FMOs) are known in animals. They add molecular oxygen to lipophilic compounds or produce reactive oxygen species (ROS). However, little information on FMOs in plants is available. Here, we characterized a tomato drought-responsive gene that showed homology to FMO, and it was designated as FMO1. FMO1 was downregulated promptly by drought and ABA treatments. Transgenic functional analysis indicated that RNAi suppression of the expression of FMO1 (FMO1-Ri) improved drought tolerance relative to wild-type (WT) plants, whereas overexpression of FMO1 (FMO1-OE) reduced drought tolerance. The FMO1-Ri plants exhibited lower ABA accumulation, higher levels of antioxidant enzyme activities, and less ROS generation compared with the WT and FMO1-OE plants under drought stress. RNA-seq transcriptional analysis revealed the differential expression levels of many drought-responsive genes that were co-expressed with FMO1, including PP2Cs, PYLs, WRKY, and LEA. Using Y2H screening, we found that FMO1 physically interacted with catalase 2 (CAT2), which is an antioxidant enzyme and confers drought resistance. Our findings suggest that tomato FMO1 negatively regulates tomato drought tolerance in the ABA-dependent pathway and modulates ROS homeostasis by directly binding to SlCAT2.

The SAH7 Homologue of the Allergen Ole e 1 Interacts with the Putative Stress Sensor SBP1 (Selenium-Binding Protein 1) in Arabidopsis thaliana

In this study, we focused on a member of the Ole e 1 domain-containing family, AtSAH7, in Arabidopsis thaliana. Our lab reports for the first time on this protein, AtSAH7, that was found to interact with Selenium-binding protein 1 (AtSBP1). We studied by GUS assisted promoter deletion analysis the expression pattern of AtSAH7 and determined that the sequence 1420 bp upstream of the transcription start can act as a minimal promoter inducing expression in vasculature tissues. Moreover, mRNA levels of AtSAH7 were acutely increased under selenite treatment in response to oxidative stress. We confirmed the aforementioned interaction in vivo, in silico and in planta. Following a bimolecular fluorescent complementation approach, we determined that the subcellular localization of the AtSAH7 and the AtSAH7/AtSBP1 interaction occur in the ER. Our results indicate the participation of AtSAH7 in a biochemical network regulated by selenite, possibly associated with responses to ROS production.

Evolutionary Analysis of StSnRK2 Family Genes and Their Overexpression in Transgenic Tobacco Improve Drought Tolerance

Sucrose non-ferment 1-related protein kinase 2 (SnRK2) is a highly conserved protein kinase in plants that plays an important role in regulating plant response to drought stress. Although it has been reported in some plants, the evolutionary relationship of potato SnRK2s and their function in drought resistance have not been systematically analyzed. In this study, molecular characteristic analysis showed that 8 StSnRK2s were distributed on six chromosomes, coding proteins were divided into three subgroups, and StSnRK2s clustered in the same subgroup had similar conserved motifs and domains. In addition, StSnRK2 has a wide range of replication events in some species, making it closer to dicots in the process of evolution. In addition, the average nonsynonymous substitution rate/synonymous substitution rate (Ka/Ks) value of SnRK2s in monocots was higher than that of dicots. The codon usage index showed that SnRK2s prefer to use cytosine 3 (C3s), guanine 3 (G3s) and GC content (GC3s) in monocots, whereas thymine 3 (T3s) and adenine 3 (A3s) are preferred in dicots. Furthermore, stress response analysis showed that the expression of StSnRK2s under different degrees of drought stress significantly correlated with one or more stress-related physiological indices, such as proline and malondialdehyde (MDA) content, superoxide dismutase (SOD) and catalase (CAT) activity, ion leakage (IL) etc. The drought resistance of StSnRK2 transgenic plants was determined to occur in the order of StSnRK2.1/2.8 > StSnRK2.2/2.5 > StSnRK2.4/2.6 > StSnRK2.3 > StSnRK2.7, was attributed to not only lower IL but also higher proline, soluble sugar contents and stress-related genes in transgenic plants compared to wild type (WT). In conclusion, this study provides useful insights into the evolution and function of StSnRK2s and lays a foundation for further study on the molecular mechanism of StSnRK2s regulating potato drought resistance.

Ascorbate-Glutathione Cycle Genes Families in Euphorbiaceae: Characterization and Evolutionary Analysis

Ascorbate peroxidase (APX), Monodehydroascorbate Reductase (MDAR), Dehydroascorbate Reductase (DHAR) and Glutathione Reductase (GR) enzymes participate in the ascorbate-glutathione cycle, which exerts a central role in the antioxidant metabolism in plants. Despite the importance of this antioxidant system in different signal transduction networks related to development and response to environmental stresses, the pathway has not yet been comprehensively characterized in many crop plants. Among different eudicotyledons, the Euphorbiaceae family is particularly diverse with some species highly tolerant to drought. Here the APX, MDAR, DHAR, and GR genes in Ricinus communis, Jatropha curcas, Manihot esculenta, and Hevea brasiliensis were identified and characterized. The comprehensive phylogenetic and genomic analyses allowed the classification of the genes into different classes, equivalent to cytosolic, peroxisomal, chloroplastic, and mitochondrial enzymes, and revealed the duplication events that contribute to the expansion of these families within plant genomes. Due to the high drought stress tolerance of Ricinus communis, the expression patterns of ascorbate-glutathione cycle genes in response to drought were also analyzed in leaves and roots, indicating a differential expression during the stress. Altogether, these data contributed to the characterization of the expression pattern and evolutionary analysis of these genes, filling the gap in the proposed functions of core components of the antioxidant mechanism during stress response in an economically relevant group of plants.

A Tea Plant (Camellia sinensis) FLOWERING LOCUS C-like Gene, CsFLC1, Is Correlated to Bud Dormancy and Triggers Early Flowering in Arabidopsis

Flowering and bud dormancy are crucial stages in the life cycle of perennial angiosperms in temperate climates. MADS-box family genes are involved in many plant growth and development processes. Here, we identified three MADS-box genes in tea plant belonging to the FLOWERING LOCUS C (CsFLC) family. We monitored CsFLC1 transcription throughout the year and found that CsFLC1 was expressed at a higher level during the winter bud dormancy and flowering phases. To clarify the function of CsFLC1, we developed transgenic Arabidopsis thaliana plants heterologously expressing 35S::CsFLC1. These lines bolted and bloomed earlier than the WT (Col-0), and the seed germination rate was inversely proportional to the increased CsFLC1 expression level. The RNA-seq of 35S::CsFLC1 transgenic Arabidopsis showed that many genes responding to ageing, flower development and leaf senescence were affected, and phytohormone-related pathways were especially enriched. According to the results of hormone content detection and RNA transcript level analysis, CsFLC1 controls flowering time possibly by regulating SOC1, AGL42, SEP3 and AP3 and hormone signaling, accumulation and metabolism. This is the first time a study has identified FLC-like genes and characterized CsFLC1 in tea plant. Our results suggest that CsFLC1 might play dual roles in flowering and winter bud dormancy and provide new insight into the molecular mechanisms of FLC in tea plants as well as other plant species.

Transcriptomics Profiling of Acer pseudosieboldianum Molecular Mechanism against Freezing Stress

Low temperature is an important environmental factor that affects the growth and development of trees and leads to the introduction of failure in the genetic improvement of trees. Acer pseudosieboldianum is a tree species that is well-known for its bright red autumn leaf color. These trees are widely used in landscaping in northeast China. However, due to their poor cold resistance, introduced A. pseudosieboldianum trees suffer severe freezing injury in many introduced environments. To elucidate the physiological indicators and molecular mechanisms associated with freezing damage, we analyzed the physiological indicators and transcriptome of A. pseudosieboldianum, using kits and RNA-Seq technology. The mechanism of A. pseudosieboldianum in response to freezing stress is an important scientific question. In this study, we used the shoots of four-year-old A. pseudosieboldianum twig seedlings, and the physiological index and the transcriptome of A. pseudosieboldianum under low temperature stress were investigated. The results showed that more than 20,000 genes were detected in A. pseudosieboldianum under low temperature (4 °C) and freezing temperatures (-10 °C, -20 °C, -30 °C, and -40 °C). There were 2505, 6021, 5125, and 3191 differential genes (DEGs) between -10 °C, -20°C, -30°C, -40 °C, and CK (4 °C), respectively. Among these differential genes, 48 genes are involved in the MAPK pathway and 533 genes are involved in the glucose metabolism pathway. In addition, the important transcription factors (MYB, AP2/ERF, and WRKY) involved in freezing stress were activated under different degrees of freezing stress. A total of 10 sets of physiological indicators of A. pseudosieboldianum were examined, including the activities of five enzymes and the accumulation of five hormones. All of the physiological indicators except SOD and GSH-Px reached their maximum values at -30 °C. The enzyme activity of SOD was highest at -10 °C, and that of GSH-Px was highest at -20 °C. Our study is the first to provide a more comprehensive understanding of the differential genes (DEGs) involved in A. pseudosieboldianum under freezing stress at different temperatures at the transcriptome level. These results may help to clarify the molecular mechanism of cold tolerance of A. pseudosieboldianum and provide new insights and candidate genes for the genetic improvement of the freezing tolerance of A. pseudosieboldianum.

Recent developments in multi-omics and breeding strategies for abiotic stress tolerance in maize (Zea mays L.)

High-throughput sequencing technologies (HSTs) have revolutionized crop breeding. The advent of these technologies has enabled the identification of beneficial quantitative trait loci (QTL), genes, and alleles for crop improvement. Climate change have made a significant effect on the global maize yield. To date, the well-known omic approaches such as genomics, transcriptomics, proteomics, and metabolomics are being incorporated in maize breeding studies. These approaches have identified novel biological markers that are being utilized for maize improvement against various abiotic stresses. This review discusses the current information on the morpho-physiological and molecular mechanism of abiotic stress tolerance in maize. The utilization of omics approaches to improve abiotic stress tolerance in maize is highlighted. As compared to single approach, the integration of multi-omics offers a great potential in addressing the challenges of abiotic stresses of maize productivity.

Transcriptome and co-expression network analyses of key genes and pathways associated with differential abscisic acid accumulation during maize seed maturation

BACKGROUND

Currently, mechanical maize kernel harvesting has not been fully utilized in developing countries including China, partly due to the absence of suitable cultivars capable of rapid desiccation during seed maturation. The initiation of rapid desiccation during seed maturation is regulated by abscisic acid (ABA). For further characterization of ABA-regulated key genes and cellular events, it is necessary to perform transcriptome analysis of maize developing embryos. The ABA synthesis-deficient mutant (vp5) and normal maize (Vp5) seeds are suitable materials for such purpose.

RESULTS

In the present work, developing vp5 and Vp5 embryos were compared by ABA content and transcriptome analyses. Quantitative analysis revealed the significant difference in ABA synthesis between both genotypes. From 29 days after pollination (DAP), ABA content increased rapidly in Vp5 embryos, but decreased gradually in vp5 embryos. At 36 DAP, ABA level in vp5 decreased to 1/4 that of Vp5, suggesting that the differential ABA levels would affect seed maturation. Comparative transcriptomic analysis has found 1019 differentially expressed genes (DEGs) between both genotypes, with the most DEGs (818) at 36 DAP. Further, weighted correlation network analysis (WGCNA) revealed eight DEGs co-expression modules. Particularly, a module was negatively correlated with ABA content in vp5 embryos. The module was mainly involved in metabolic and cellular processes, and its hub genes encoded thiamine, NPF proteins, calmodulin, metallothionein etc. Moreover, the expression of a set of key genes regulated by ABA was further verified by RT-qPCR. The results of the present work suggested that because of ABA deficiency, the vp5 seeds maintained strong metabolic activities and lacked dormancy initiation during seed maturation.

CONCLUSION

Transcriptome and WGCNA analyses revealed significant ABA-related changes in metabolic pathways and DEGs between vp5 and Vp5 during seed maturation. The results would provide insights for elucidating the molecular mechanism of ABA signaling and developing high dehydration tolerance maize suitable for mechanical harvesting.

Thermo-Priming Mediated Cellular Networks for Abiotic Stress Management in Plants

Plants can adapt to different environmental conditions and can survive even under very harsh conditions. They have developed elaborate networks of receptors and signaling components, which modulate their biochemistry and physiology by regulating the genetic information. Plants also have the abilities to transmit information between their different parts to ensure a holistic response to any adverse environmental challenge. One such phenomenon that has received greater attention in recent years is called stress priming. Any milder exposure to stress is used by plants to prime themselves by modifying various cellular and molecular parameters. These changes seem to stay as memory and prepare the plants to better tolerate subsequent exposure to severe stress. In this review, we have discussed the various ways in which plants can be primed and illustrate the biochemical and molecular changes, including chromatin modification leading to stress memory, with major focus on thermo-priming. Alteration in various hormones and their subsequent role during and after priming under various stress conditions imposed by changing climate conditions are also discussed.

Transcriptome Analysis of Populus euphratica under Salt Treatment and PeERF1 Gene Enhances Salt Tolerance in Transgenic Populus alba × Populus glandulosa

Populus euphratica is mainly distributed in desert environments with dry and hot climate in summer and cold in winter. Compared with other poplars, P. euphratica is more resistant to salt stress. It is critical to investigate the transcriptome and molecular basis of salt tolerance in order to uncover stress-related genes. In this study, salt-tolerant treatment of P. euphratica resulted in an increase in osmo-regulatory substances and recovery of antioxidant enzymes. To improve the mining efficiency of candidate genes, the analysis combining both the transcriptome WGCNA and the former GWAS results was selected, and a range of key regulatory factors with salt resistance were found. The PeERF1 gene was highly connected in the turquoise modules with significant differences in salt stress traits, and the expression levels were significantly different in each treatment. For further functional verification of PeERF1, we obtained stable overexpression and dominant suppression transgenic lines by transforming into Populus alba × Populusglandulosa. The growth and physiological characteristics of the PeERF1 overexpressed plants were better than that of the wild type under salt stress. Transcriptome analysis of leaves of transgenic lines and WT revealed that highly enriched GO terms in DEGs were associated with stress responses, including abiotic stimuli responses, chemical responses, and oxidative stress responses. The result is helpful for in-depth analysis of the salt tolerance mechanism of poplar. This work provides important genes for poplar breeding with salt tolerance.

Nitric Oxide and Abscisic Acid Mediate Heat Stress Tolerance through Regulation of Osmolytes and Antioxidants to Protect Photosynthesis and Growth in Wheat Plants

Nitric oxide (NO) and abscisic acid (ABA) play a significant role to combat abiotic stress. Application of 100 µM sodium nitroprusside (SNP, NO donor) or ABA alleviated heat stress effects on photosynthesis and growth of wheat (Triticum aestivum L.) plants exposed to 40 °C for 6 h every day for 15 days. We have shown that ABA and NO synergistically interact to reduce the heat stress effects on photosynthesis and growth via reducing the content of H2O2 and thiobarbituric acid reactive substances (TBARS), as well as maximizing osmolytes production and the activity and expression of antioxidant enzymes. The inhibition of NO and ABA using c-PTIO (2-4 carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and fluridone (Flu), respectively, reduced the osmolyte and antioxidant metabolism and heat stress tolerance. The inhibition of NO significantly reduced the ABA-induced osmolytes and antioxidant metabolism, exhibiting that the function of ABA in the alleviation of heat stress was NO dependent and can be enhanced with NO supplementation.Thus, regulating the activity and expression of antioxidant enzymes together with osmolytes production could act as a possible strategy for heat tolerance.

Synthesis of Abscisic Acid in Neopyropia yezoensis and Its Regulation of Antioxidase Genes Expressions Under Hypersaline Stress

Abscisic acid (ABA) is regarded as crucial for plant adaptation to water-limited conditions and it functions evolutionarily conserved. Thus, insights into the synthesis of ABA and its regulation on downstream stress-responsive genes in Neopyropia yezoensis, a typical Archaeplastida distributed in intertidal zone, will improve the knowledge about how ABA signaling evolved in plants. Here, the variations in ABA contents, antioxidant enzyme activities and expression of the target genes were determined under the presence of exogenous ABA and two specific inhibitors of the ABA precursor synthesis. ABA content was down-regulated under the treatments of each or the combination of the two inhibitors. Antioxidant enzyme activities like SOD, CAT and APX were decreased slightly with inhibitors, but up-regulated when the addition of exogenous ABA. The quantitative assays using real-time PCR (qRT-PCR) results were consistent with the enzyme activities. All the results suggested that ABA can also alleviate oxidative stress in N. yezoensis as it in terrestrial plant. Combined with the transcriptome assay, it was hypothesized that ABA is synthesized in N. yezoensis via a pathway that is similar to the carotenoid pathway in higher plants, and both the MVA and that the MEP pathways for isoprenyl pyrophosphate (IPP) synthesis likely exist simultaneously. The ABA signaling pathway in N. yezoensis was also analyzed from an evolutionary standpoint and it was illustrated that the emergence of the ABA signaling pathway in this alga is an ancestral one. In addition, the presence of the ABRE motif in the promoter region of antioxidase genes suggested that the antioxidase system is regulated by the ABA signaling pathway.

Increasing yield on dry fields: molecular pathways with growing potential

Drought stress constitutes one of the major constraints to agriculture all over the world, and its devastating effect is only expected to increase in the following years due to climate change. Concurrently, the increasing food demand in a steadily growing population requires a proportional increase in yield and crop production. In the past, research aimed to increase plant resilience to severe drought stress. However, this often resulted in stunted growth and reduced yield under favorable conditions or moderate drought. Nowadays, drought tolerance research aims to maintain plant growth and yield under drought conditions. Overall, recently deployed strategies to engineer drought tolerance in the lab can be classified into a 'growth-centered' strategy, which focuses on keeping growth unaffected by the drought stress, and a 'drought resilience without growth penalty' strategy, in which the main aim is still to boost drought resilience, while limiting the side effects on plant growth. In this review, we put the scope on these two strategies and some molecular players that were successfully engineered to generate drought-tolerant plants: abscisic acid, brassinosteroids, cytokinins, ethylene, ROS scavenging genes, strigolactones, and aquaporins. We discuss how these pathways participate in growth and stress response regulation under drought. Finally, we present an overview of the current insights and future perspectives in the development of new strategies to improve drought tolerance in the field.

Effect of soil sulfamethoxazole on strawberry (Fragaria ananassa): Growth, health risks and silicon mitigation

The negative impact of antibiotic pollution on the agricultural system and human health is a hot issue in the world. However, little information is available on the antibiotics toxicity mechanism and the role of silicon (Si) to alleviate the antibiotics toxicity. In this study, strawberry (Fragaria ananassa) showed excitatory response to low-dose SMZ (1 mg L^-1), but strawberry root and photosynthetic efficiency were damaged under high level. When SMZ level exceeded 10 mg L^-1, H₂0₂, O₂^-, MDA and relative conductivity increased, while SOD and CAT activities first increased and then decreased. SMZ accumulated more in roots and fruits, but less in stems, and the accumulation increased with the increase of SMZ-dose. Under 1 mg L^-1 SMZ, the SMZ accumulation in fruits was 110.54 μg kg^-1, which exceeded the maximum residue limit. SMZ can induce the expression of sul1, sul2 and intI1, and intI1 had the highest abundance. Exogenous application of Si alleviated the toxicity of SMZ, which is mainly related to the degradation of SMZ in soil and the reduction of SMZ absorption by strawberry. In addition, Si relieved root damage, promoted the increase of photosynthetic efficiency, and improved the antioxidant system to resist SMZ toxicity.

Synthesis and regulation of auxin and abscisic acid in maize

Indole-3-acetic acid (IAA), the primary auxin in higher plants, and abscisic acid (ABA) play crucial roles in the ability of maize (Zea mays L.) to acclimatize to various environments by mediating growth, development, defense and nutrient allocation. Although understanding the biochemical reactions for IAA and ABA biosynthesis and signal transduction has progressed, the mechanisms by which auxin and ABA are synthesized and transduced in maize have not been fully elucidated to date. The synthesis and signal transduction pathway of IAA and ABA in maize can be analyzed using an existing model. This article focuses on the research progress toward understanding the synthesis and signaling pathways of IAA and ABA, as well as IAA and ABA regulation of maize growth, providing insight for future development and the significance of IAA and ABA for maize improvement.

Pre-harvest sprouting in cereals: genetic and biochemical mechanisms

With the growth of the global population and the increasing frequency of natural disasters, crop yields must be steadily increased to enhance human adaptability to risks. Pre-harvest sprouting (PHS), a term mainly used to describe the phenomenon in which grains germinate on the mother plant directly before harvest, is a serious global problem for agricultural production. After domestication, the dormancy level of cultivated crops was generally lower than that of their wild ancestors. Although the shortened dormancy period likely improved the industrial performance of cereals such as wheat, barley, rice, and maize, the excessive germination rate has caused frequent PHS in areas with higher rainfall, resulting in great economic losses. Here, we systematically review the causes of PHS and its consequences, the major indicators and methods for PHS assessment, and emphasize the biological significance of PHS in crop production. Wheat quantitative trait loci functioning in the control of PHS are also comprehensively summarized in a meta-analysis. Finally, we use Arabidopsis as a model plant to develop more complete PHS regulatory networks for wheat. The integration of this information is conducive to the development of custom-made cultivated lines suitable for different demands and regions, and is of great significance for improving crop yields and economic benefits.

Emerging warriors against salinity in plants: Nitric oxide and hydrogen sulphide

The agriculture sector is vulnerable to various environmental stresses, which significantly affect plant growth, performance, and development. Abiotic stresses, such as salinity and drought, cause severe losses in crop productivity worldwide. Soil salinity is a major stress suppressing plant development through osmotic stress accompanied by ion toxicity, nutritional imbalance, and oxidative stress. Various defense mechanisms like osmolytes accumulations, activation of stress-induced genes, and transcription factors, production of plant growth hormones, accumulation of antioxidants, and redox defense system in plants are responsible for combating salt stress. Nitric oxide (NO) and hydrogen sulphide (H₂ S) have emerged as novel bioactive gaseous signaling molecules that positively impact seed germination, homeostasis, plant metabolism, growth, and development, and are involved in several plant acclimation responses to impart stress tolerance in plants. NO and H₂ S trigger cell signaling by activating a cascade of biochemical events that result in plant tolerance to environmental stresses. NO- and H₂ S-mediated signaling networks, interactions, and crosstalks facilitate stress tolerance in plants. Research on the roles and mechanisms of NO and H₂ S as challengers of salinity is entering an exponential exploration era. The present review focuses on the current knowledge of the mechanisms of stress tolerance in plants and the role of NO and H₂ S in adaptive plant responses to salt stress and provides an overview of the signaling mechanisms and interplay of NO and H₂ S in the regulation of growth and development as well as modulation of defense responses in plants and their long term priming effects for imparting salinity tolerance in plants.

Effect of the pharmaceuticals diclofenac and lamotrigine on stress responses and stress gene expression in lettuce (Lactuca sativa) at environmentally relevant concentrations

Vegetable crops irrigated with treated wastewater can take up the environmentally persistent pharmaceuticals diclofenac and lamotrigine. This study aimed at quantifying the uptake and translocation of the two pharmaceuticals in lettuce (Lactuca sativa) as well as on the elucidation of the molecular and physiological changes triggered by them. Therefore, plants were cultivated in a phytochamber in hydroponic systems under controlled conditions and treated independently with diclofenac (20 μg L-1) and lamotrigine (60 μg L-1) for 48 h. A low translocation of lamotrigine but not of diclofenac or its metabolite 4'-hydroxydiclofenac to leaves was observed, which corresponded with the expression of stress related genes only in roots of diclofenac treated plants. We observed an oxidative burst in roots and leaves occurring around the same time point when lamotrigine was detected in leaves. This could be responsible for the significantly changed gene expression pattern in both tissues. Our results showed for the first time that pharmaceuticals like lamotrigine or diclofenac might act as signals or zeitgebers, affecting the circadian expression of stress related genes in lettuce possibly causing a repressed physiological status of the plant.

Transcriptomic analysis reveals somatic embryogenesis-associated signaling pathways and gene expression regulation in maize (Zea mays L.)

Transcriptome analysis of maize embryogenic callus and somatic embryos reveals associated genes reprogramming, hormone signaling pathways and transcriptional regulation involved in somatic embryogenesis in maize. Somatic embryos are widely utilized in propagation and genetic engineering of crop plants. In our laboratory, an elite maize inbred line Y423 that could generate intact somatic embryos was obtained and applied to genetic transformation. To enhance our understanding of regulatory mechanisms during maize somatic embryogenesis, we used RNA-based sequencing (RNA-seq) to characterize the transcriptome of immature embryo (IE), embryogenic callus (EC) and somatic embryo (SE) from maize inbred line Y423. The number of differentially expressed genes (DEGs) in three pairwise comparisons (IE-vs-EC, IE-vs-SE and EC-vs-SE) was 5767, 7084 and 1065, respectively. The expression patterns of DEGs were separated into eight major clusters. Somatic embryogenesis associated genes were mainly grouped into cluster A or B with an expression trend toward up-regulation during dedifferentiation. GO annotation and KEGG pathway analysis revealed that DEGs were implicated in plant hormone signal transduction, stress response and metabolic process. Among the differentially expressed transcription factors, the most frequently represented families were associated with the common stress response or related to cell differentiation, embryogenic patterning and embryonic maturation processes. Genes include hormone response/transduction and stress response, as well as several transcription factors were discussed in this study, which may be potential candidates for further analyses regarding their roles in somatic embryogenesis. Furthermore, the temporal expression patterns of candidate genes were analyzed to reveal their roles in somatic embryogenesis. This transcriptomic data provide insights into future functional studies, which will facilitate further dissections of the molecular mechanisms that control maize somatic embryogenesis.

Stress responses and biological residues of sulfanilamide antibiotics in Arabidopsis thaliana

Sulfonamides (SAs) are antibiotics widely used in clinical practice, livestock and poultry production, and the aquaculture industry. The compounds enter the soil environment largely through livestock and poultry manure application to farmland. SAs not only affect plant growth, but also pose a potential threat to human health through SA residues in plant tissues. In particular, sulfamethoxazole (SMZ) has been classified as a Category 3 carcinogen by the World Health Organization, and thus its soil ecological toxicity and possible health risks are of concern. Using A. thaliana as a model plant, stress responses and biological residues of sulfadiazine (SD), sulfametoxydiazine (SMD), and SMZ were investigated in the present study. Root length and aboveground plant biomass were significantly inhibited by the three types of SA, whereas lateral roots exposed to SMD grew vigorously. The contents of chlorophyll a and chlorophyll b and photosystem II maximum photochemical quantum yield declined with increase in drug concentration, which indicated that exposure to SAs affected photosynthesis and inhibited chlorophyll synthesis in A. thaliana. With increase in drug concentration, reactive oxygen species (ROS) accumulation in the leaves increased significantly. Activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were activated at low SA concentrations, but increased lipid peroxidation occurred with increase in SA concentration. Of the three compounds, SMZ was the most toxic to A. thaliana, followed by SD, and SMD was the least toxic. The results indicated that the risk of SMD entering an organism through the food chain is greater than that for SMZ and SD.

ROS Homeostasis in Abiotic Stress Tolerance in Plants

Climate change-induced abiotic stress results in crop yield and production losses. These stresses result in changes at the physiological and molecular level that affect the development and growth of the plant. Reactive oxygen species (ROS) is formed at high levels due to abiotic stress within different organelles, leading to cellular damage. Plants have evolved mechanisms to control the production and scavenging of ROS through enzymatic and non-enzymatic antioxidative processes. However, ROS has a dual function in abiotic stresses where, at high levels, they are toxic to cells while the same molecule can function as a signal transducer that activates a local and systemic plant defense response against stress. The effects, perception, signaling, and activation of ROS and their antioxidative responses are elaborated in this review. This review aims to provide a purview of processes involved in ROS homeostasis in plants and to identify genes that are triggered in response to abiotic-induced oxidative stress. This review articulates the importance of these genes and pathways in understanding the mechanism of resistance in plants and the importance of this information in breeding and genetically developing crops for resistance against abiotic stress in plants.

Abscisic Acid-Enemy or Savior in the Response of Cereals to Abiotic and Biotic Stresses?

Abscisic acid (ABA) is well-known phytohormone involved in the control of plant natural developmental processes, as well as the stress response. Although in wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) its role in mechanism of the tolerance to most common abiotic stresses, such as drought, salinity, or extreme temperatures seems to be fairly well recognized, not many authors considered that changes in ABA content may also influence the sensitivity of cereals to adverse environmental factors, e.g., by accelerating senescence, lowering pollen fertility, and inducing seed dormancy. Moreover, recently, ABA has also been regarded as an element of the biotic stress response; however, its role is still highly unclear. Many studies connect the susceptibility to various diseases with increased concentration of this phytohormone. Therefore, in contrast to the original assumptions, the role of ABA in response to biotic and abiotic stress does not always have to be associated with survival mechanisms; on the contrary, in some cases, abscisic acid can be one of the factors that increases the susceptibility of plants to adverse biotic and abiotic environmental factors.

Different Roles of Auxins in Somatic Embryogenesis Efficiency in Two Picea Species

The effects of auxins 2,4-D (2,4-dichlorophenoxyacetic acid), NAA (1-naphthaleneacetic acid) or picloram (4-amino-3,5,6-trichloropicolinic acid; 9 µM) and cytokinin BA (benzyloadenine; 4.5 µM) applied in the early stages of somatic embryogenesis (SE) on specific stages of SE in Picea abies and P. omorika were investigated. The highest SE initiation frequency was obtained after 2,4-D application in P. omorika (22.00%) and picloram application in P. abies (10.48%). NAA treatment significantly promoted embryogenic tissue (ET) proliferation in P. abies, while 2,4-D treatment reduced it. This reduction was related to the oxidative stress level, which was lower with the presence of NAA in the proliferation medium and higher with the presence of 2,4-D. The reduced oxidative stress level after NAA treatment suggests that hydrogen peroxide (H2O2) acts as a signalling molecule and promotes ET proliferation. NAA and picloram in the proliferation medium decreased the further production and maturation of P. omorika somatic embryos compared with that under 2,4-D. The quality of the germinated P. abies embryos and their development into plantlets depended on the auxin type and were the highest in NAA-originated embryos. These results show that different auxin types can generate different physiological responses in plant materials during SE in both spruce species.

Maize NCP1 negatively regulates drought and ABA responses through interacting with and inhibiting the activity of transcription factor ABP9

NCP1, a NINJA family protein lacking EAR motif, acts as a negative regulator of ABA signaling by interacting with and inhibiting the activity of transcriptional activator ABP9. The phytohormone abscisic acid plays a pivotal role in regulating plant responses to a variety of abiotic stresses including drought and salinity. Maize ABP9 is an ABRE-binding bZIP transcription activator that enhances plant tolerance to multiple stresses by positively regulating ABA signaling, but the molecular mechanism by which ABP9 is regulated in mediating ABA responses remains unknown. Here, we report the identification of an ABP9-interacting protein, named ABP Nine Complex Protein 1 (NCP1) and its functional characterization. NCP1 belongs to the recently identified NINJA family proteins, but lacks the conserved EAR motif, which is a hallmark of this class of transcriptional repressors. In vitro and in vivo assays confirmed that NCP1 physically interacts with ABP9 and that they are co-localized in the nucleus. In addition, NCP1 and ABP9 are similarly induced with similar patterns by ABA treatment and osmotic stress. Interestingly, NCP1 over-expressing Arabidopsis plants exhibited a reduced sensitivity to ABA and decreased drought tolerance. Transient assay in maize protoplasts showed that NCP1 inhibits the activity of ABP9 in activating ABRE-mediated reporter gene expression, a notion further supported by genetic analysis of drought and ABA responses in the transgenic plants over-expressing both ABP9 and NCP1. These data together suggest that NCP1 is a novel negative regulator of ABA signaling via interacting with and inhibiting the activity of ABP9.

The barley transcription factor HvMYB1 is a positive regulator of drought tolerance

Transcription factors such as MYB have previously been associated with the plant response to drought. In this work, studies on the function of the barley (Hordeum vulgare L.) transcription factor HvMYB1 show that gene expression is upregulated in wildtype barley roots and leaves under drought and osmotic stress. Transgenic barley plants that overexpress HvMYB1 were found to be more resistant to drought, showing enhanced relative water content and reduced water loss rate and stomatal conductance as compared to control plants. Levels of the osmolyte proline were enhanced as was expression of dehydrin HvDNH6 in the transgenic lines under drought conditions. The levels of the reactive oxygen species H₂O₂ were enhanced in wildtype roots and leaves by drought, but less so in the HvMYB1 overexpressing lines. Enzyme activity of the low affinity H₂O₂ degrading enzyme catalase (EC 1.11.1.6) was also lower in droughted HvMYB1 overexpressing lines. Gene expression of the high affinity ROS scavengers ASCORBATE PEROXIDASE and GLUTATHIONE PEROXIDASE was found to be constitutively high in the overexpressing lines, whereas CATALASE gene expression was similar to the control plants. These results suggest a role for HvMYB1 in protecting plants against drought in the vegetative plant by acting as a mediator of abscisic acid action.

Role of calreticulin in biotic and abiotic stress signalling and tolerance mechanisms in plants

Calreticulin (CRT) is calcium binding protein of endoplasmic reticulum (ER) which performs plethora of functions besides it's role as molecular chaperone. Among the three different isoforms of this protein, CRT3 is most closely related to primitive CRT gene of higher plants. Based on their distinct structural and functional organisation, the plant CRTs have been known to contain three different domains: N, P and the C domain. The domain organisation and various biochemical characterstics of plant and animal CRTs are common with the exception of some differences. In plant calreticulin, the important N-glycosylation site(s) are replaced by the glycan chain(s) and several consensus sequences for in vitro phosphorylation by protein kinase CK2 (casein kinase-2), are also present unlike the animal calreticulin. Biotic and abiotic stresses play a significant role in bringing down the crop production. The role of various phytohormones in defense against fungal pathogens is well documented. CRT3 has been reported to play important role in protecting the plants against fungal and bacterial pathogens and in maintaining plant innate immunity. There is remarkable crosstalk between CRT mediated signalling and biotic, abiotic stress, and phytohormone mediated signalling pathways The role of CRT mediated pathway in mitigating biotic and abiotic stress can be further explored in plants so as to strategically modify it for development of stress tolerant plants.

Localization and expression analysis of a novel catalase from Triticum monococcum TmCAT1 involved in response to different environmental stresses

Catalase proteins play a crucial role in detoxifying hydrogen peroxide, generated during plant growth, and in response to various environmental stresses. Despite their importance, little is known about their localization and expression in wheat. In this study, we identified and characterized a novel peroxisomal catalase gene from Triticum monococcum, designated as TmCAT1. Phylogenetic analysis revealed that TmCAT1 shared high identity with TdCAT1 and other plant catalases belonging to subfamily 1. We predicted the 3D structure model and the oligomerization arrangement of TmCAT1. Besides, we displayed an arrangement in asymmetric unit, which involved interactions including, mainly, residues from N-terminal domain. Interestingly, sequence analysis indicated that TmCAT1, like TdCAT1, had the peroxisomal targeting signal (PTS1) around its C-terminus. Transient expression of TmCAT1-GFP and TdCAT1-GFP in tobacco leaves revealed that the two fused proteins are targeted into peroxisomes. However, the truncated forms lacking the tripeptide QKL remained in the cytosol. Concerning the expression profile analysis, TmCAT1 is expressed especially in leaves in normal condition. On the other hand, it is up-regulated by different stress incorporating salt, osmotic, oxidative, heavy metal and hormones stresses. Functional analysis by heterologous expression in yeast cells showed that TmCAT1 improved tolerance to multiple abiotic stresses. The presence of important cis-regulatory elements in the promoter region of TmCAT1 strongly reinforces the interest of this gene in plant adaptation to various stresses.

Is There A Role for Abscisic Acid, A Proven Anti-Inflammatory Agent, in the Treatment of Ischemic Retinopathies?

Ischemic retinopathies (IRs) are the main cause of severe visual impairment and sight loss, and are characterized by loss of blood vessels, accompanied by hypoxia, and neovascularization. Actual therapies, based on anti-vascular endothelial growth factor (VEGF) strategies, antioxidants or anti-inflammatory therapies are only partially effective or show some adverse side effects. Abscisic acid (ABA) is a phytohormone present in vegetables and fruits that can be naturally supplied by the dietary intake and has been previously studied for its benefits to human health. It has been demonstrated that ABA plays a key role in glucose metabolism, inflammation, memory and tumor growth. This review focuses on a novel and promising role of ABA as a potential modulator of angiogenesis, oxidative status and inflammatory processes in the retina, which are the most predominant characteristics of the IRs. Thus, this nutraceutical compound might shed some light in new therapeutic strategies focused in the prevention or amelioration of IRs-derived pathologies.

An Overview of the Genetics of Plant Response to Salt Stress: Present Status and the Way Forward

Salinity is one of the major threats faced by the modern agriculture today. It causes multidimensional effects on plants. These effects depend upon the plant growth stage, intensity, and duration of the stress. All these lead to stunted growth and reduced yield, ultimately inducing economic loss to the farming community in particular and to the country in general. The soil conditions of agricultural land are deteriorating at an alarming rate. Plants assess the stress conditions, transmit the specific stress signals, and then initiate the response against that stress. A more complete understanding of plant response mechanisms and their practical incorporation in crop improvement is an essential step towards achieving the goal of sustainable agricultural development. Literature survey shows that investigations of plant stresses response mechanism are the focus area of research for plant scientists. Although these efforts lead to reveal different plant response mechanisms against salt stress, yet many questions still need to be answered to get a clear picture of plant strategy to cope with salt stress. Moreover, these studies have indicated the presence of a complicated network of different integrated pathways. In order to work in a progressive way, a review of current knowledge is critical. Therefore, this review aims to provide an overview of our understanding of plant response to salt stress and to indicate some important yet unexplored dynamics to improve our knowledge that could ultimately lead towards crop improvement.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

Allelic diversity of phytoene synthase gene influences the transcription level in citrus fruit among a citrus F1 hybrid population

Phytoene synthase (PSY) is one of the key regulatory enzyme on the biosynthesis and accumulation of carotenoid in citrus fruits. The transcriptional diversity of PSY is mainly attributed to the structural variation in promoter region among PSY alleles. In aim to clarify how this transcriptional diversity is regulated among them, PSY alleles responsible for carotenoid biosynthesis in the fruits are characterized and their promoter sequences were compared. Based on gene structure and expression pattern of PSY homologues on the clementine mandarin genome sequence, PSY alleles responsible for carotenoid biosynthesis are derived from a single locus in the scaffold 6. AG mapping population possessed four PSY alleles derived from parent lines of A255 and G434, and their F₁ individuals with PSY-g2 allele tended to have low transcription level. From sequence comparison of their promoter regions, the cis-motif alternation from MYBPZM to RAV1AAT might be a candidate to influence the transcription level. Among the ancestral pedigree varieties of AG mapping population, the transcription level of PSY correlated with genotypes of MYBPZM and RAV1AAT motifs in the promoter region of PSY alleles, so that homozygous genotype of MYBPZM showed higher transcription level while heterozygous genotype of MYBPZM and RAV1AAT showed lower transcription level.

A Microsomal Proteomics View of H₂O₂- and ABA-Dependent Responses

The plant hormone abscisic acid (ABA) modulates a number of plant developmental processes and responses to stress. In planta, ABA has been shown to induce reactive oxygen species (ROS) production through the action of plasma membrane-associated nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases. Although quantitative proteomics studies have been performed to identify ABA- or hydrogen peroxide (H₂O₂)-dependent proteins, little is known about the ABA- and H₂O₂-dependent microsomal proteome changes. Here, we examined the effect of 50 µM of either H₂O₂ or ABA on the Arabidopsis microsomal proteome using tandem mass spectrometry and identified 86 specifically H₂O₂-dependent, and 52 specifically ABA-dependent proteins that are differentially expressed. We observed differential accumulation of proteins involved in the tricarboxylic acid (TCA) cycle notably in response to H₂O₂. Of these, aconitase 3 responded to both H₂O₂ and ABA. Additionally, over 30 proteins linked to RNA biology responded significantly to both treatments. Gene ontology categories such as ‘response to stress’ and ‘transport’ were enriched, suggesting that H₂O₂ or ABA directly and/or indirectly cause complex and partly overlapping cellular responses. Data are available via ProteomeXchange with identifier PXD006513.

Exposure to elevated sea-surface temperatures below the bleaching threshold impairs coral recovery and regeneration following injury

Elevated sea surface temperatures (SSTs) are linked to an increase in the frequency and severity of bleaching events due to temperatures exceeding corals’ upper thermal limits. The temperatures at which a breakdown of the coral-Symbiodinium endosymbiosis (coral bleaching) occurs are referred to as the upper thermal limits for the coral species. This breakdown of the endosymbiosis results in a reduction of corals’ nutritional uptake, growth, and tissue integrity. Periods of elevated sea surface temperature, thermal stress and coral bleaching are also linked to increased disease susceptibility and an increased frequency of storms which cause injury and physical damage to corals. Herein we aimed to determine the capacity of corals to regenerate and recover from injuries (removal of apical tips) sustained during periods of elevated sea surface temperatures which result in coral stress responses, but which do not result in coral bleaching (i.e., sub-bleaching thermal stress events). In this study, exposure of the species Acropora aspera to an elevated SST of 32 °C (2 °C below the bleaching threshold, 34 °C) was found to result in reduced fluorescence of green fluorescent protein (GFP), reduced skeletal calcification and a lack of branch regrowth at the site of injury, compared to corals maintained under ambient SST conditions (26 °C). Corals maintained under normal, ambient, sea surface temperatures expressed high GFP fluorescence at the injury site, underwent a rapid regeneration of the coral branch apical tip within 12 days of sustaining injury, and showed extensive regrowth of the coral skeleton. Taken together, our results have demonstrated that periods of sustained increased sea surface temperatures, below the corals’ bleaching threshold but above long-term summertime averages, impair coral recovery from damage, regardless of the onset or occurrence of coral bleaching.

Sugarcane Water Stress Tolerance Mechanisms and Its Implications on Developing Biotechnology Solutions

Sugarcane is a unique crop with the ability to accumulate high levels of sugar and is a commercially viable source of biomass for bioelectricity and second-generation bioethanol. Water deficit is the single largest abiotic stress affecting sugarcane productivity and the development of water use efficient and drought tolerant cultivars is an imperative for all major sugarcane producing countries. This review summarizes the physiological and molecular studies on water deficit stress in sugarcane, with the aim to help formulate more effective research strategies for advancing our knowledge on genes and mechanisms underpinning plant response to water stress. We also overview transgenic studies in sugarcane, with an emphasis on the potential strategies to develop superior sugarcane varieties that improve crop productivity in drought-prone environments.

Expression profile of desiccation tolerance factors in intertidal seaweed species during the tidal cycle

The transcriptional modulation of desiccation tolerance factors in P. orbicularis explains its successful recuperation after water deficit. Differential responses to air exposure clarify seaweed distribution along intertidal rocky zones. Desiccation-tolerant seaweed species, such as Pyropia orbicularis, can tolerate near 96% water loss during air exposure. To understand the phenotypic plasticity of P. orbicularis to desiccation, several tolerance factors were assessed by RT-qPCR, Western-blot analysis, and enzymatic assays during the natural desiccation-rehydration cycle. Comparative enzymatic analyses were used to evidence differential responses between P. orbicularis and desiccation-sensitive species. The results showed that during desiccation, the relative mRNA levels of genes associated with basal metabolism [trehalose phosphate synthase (tps) and pyruvate dehydrogenase (pdh)] were overexpressed in P. orbicularis. Transcript levels related to antioxidant metabolism [peroxiredoxin (prx); thioredoxin (trx); catalase (cat); lipoxygenase (lox); ferredoxin (fnr); glutathione S-transferase (gst)], cellular detoxification [ABC transporter (abc) and ubiquitin (ubq)], and signal transduction [calmodulin (cam)] increased approximately 15- to 20-fold, with the majority returning to basal levels during the final hours of rehydration. In contrast, actin (act) and transcription factor 1 (tf1) transcripts were down-regulated. ABC transporter protein levels increased in P. orbicularis during desiccation, whereas PRX transcripts decreased. The antioxidant enzymes showed higher specific activity in P. orbicularis under desiccation, and sensitive species exhibited enzymatic inactivation and scarce ABC and PRX protein detection following prolonged desiccation. In conclusion, the reported findings contribute towards understanding the ecological distribution of intertidal seaweeds at the molecular and functional levels.

Arabidopsis ABI5 plays a role in regulating ROS homeostasis by activating CATALASE 1 transcription in seed germination

It has been known that ABA INSENSITIVE 5 (ABI5) plays a vital role in regulating seed germination. In the present study, we showed that inhibition of the catalase activity with 3-amino-1,2,4-triazole (3-AT) inhibits seed germination of Col-0, abi5 mutants and ABI5-overexpression transgenic lines. Compared with Col-0, the seeds of abi5 mutants showed more sensitive to 3-AT during seed germination, while the seeds of ABI5-overexpression transgenic lines showed more insensitive. H₂O₂ showed the same effect on seed germination of Col-0, abi5 mutants and ABI5-overexpression transgenic lines as 3-AT. These results suggest that ROS is involved in the seed germination mediated by ABI5. Further, we observed that T-DNA insertion mutants of the three catalase members in Arabidopsis displayed 3-AT-insensitive or -hypersensitive phenotypes during seed germination, suggesting that these catalase members regulate ROS homeostasis in a highly complex way. ABI5 affects reactive oxygen species (ROS) homeostasis by affecting CATALASE expression and catalase activity. Furthermore, we showed that ABI5 directly binds to the CAT1 promoter and activates CAT1 expression. Genetic evidence supports the idea that CAT1 functions downstream of ABI5 in ROS signaling during seed germination. RNA-sequencing analysis indicates that the transcription of the genes involved in ROS metabolic process or genes responsive to ROS stress is impaired in abi5-1 seeds. Additionally, expression changes in some genes correlative to seed germination were showed due to the change in ABI5 expression under 3-AT treatment. Together, all the findings suggest that ABI5 regulates seed germination at least partly by affecting ROS homeostasis.