Response Of Seedlings Research Articles

Transcriptome analysis suggested that lncRNAs regulate rapeseed seedlings in responding to drought stress by coordinating the phytohormone signal transduction pathways

The growth, yield, and seed quality of rapeseed are negatively affected by drought stress. Therefore, it is of great value to understand the molecular mechanism behind this phenomenon. In a previous study, long non-coding RNAs (lncRNAs) were found to play a key role in the response of rapeseed seedlings to drought stress. However, many questions remained unanswered. This study was the first to investigate the expression profile of lncRNAs not only under control and drought treatment, but also under the rehydration treatment. A total of 381 differentially expressed lncRNA and 10,253 differentially expressed mRNAs were identified in the comparison between drought stress and control condition. In the transition from drought stress to rehydration, 477 differentially expressed lncRNAs and 12,543 differentially expressed mRNAs were detected. After identifying the differentially expressed (DE) lncRNAs, the comprehensive lncRNAs-engaged network with the co-expressed mRNAs in leaves under control, drought and rehydration was investigated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of co-expressed mRNAs identified the most significant pathways related with plant hormones (expecially abscisic acid, auxin, cytokinins, and gibberellins) in the signal transduction. The genes, co-expressed with the most-enriched DE-lncRNAs, were considered as the most effective candidates in the water-loss and water-recovery processes, including protein phosphatase 2 C (PP2C), ABRE-binding factors (ABFs), and SMALL AUXIN UP-REGULATED RNAs (SAURs). In summary, these analyses clearly demonstrated that DE-lncRNAs can act as a regulatory hub in plant-water interaction by controlling phytohormone signaling pathways and provided an alternative way to explore the complex mechanisms of drought tolerance in rapeseed.

Effect of sugarcane bagasse biochar on soybean germination and initial growth

Biochar is known as an excellent soil conditioner and a powerful carbon sequestration tool. However, to expand its use, it is necessary to understand potential adverse effects. To better address this issue, biochar was prepared from sugarcane bagasse. The effect of biochar on the germination of soybean seeds was evaluated, and a greenhouse experiment was conducted to assess the response of soybean seedlings to biochar application at different rates (CK, 0% w/w; BC1, 1% w/w; BC3, 3% w/w; and BC5, 5% w/w). Thirty days after sowing, growth parameters, soil physicochemical attributes, and microbiota were evaluated. The biochar exhibited a low O/C ratio (0.18) and an irregular porous surface, which promoted improvements in the soil's physical, chemical, and biological attributes. It also demonstrated no phytotoxic effects in germination tests for application rates up to 50 t/ha. The results of the soybean cultivation showed that the BC3 and BC5 treatments significantly increased the fresh mass of the aerial part by 64% and 86%, respectively, compared to CK. These treatments also significantly increased the fresh mass of the root system by 23% and 423%, respectively. These results highlight the potential of biochar in promoting early soybean development.

Metabolic profiling of Citrus maxima L. seedlings in response to cadmium stress using UPLC-QTOF-MS

Cadmium (Cd) pollution significantly reduces agricultural crop yields. In our research, metabolomic changes in Citrus maxima L. subjected to Cd stress were investigated using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) in tandem with multivariate analytical techniques. This integrative method, coupled with physiological evaluations, aimed to elucidate the core adaptive mechanisms to Cd stress. We found that under Cd stress, C. maxima seedlings exhibited elevated levels of reactive oxygen species, malondialdehyde, and electrolyte leakage. Furthermore, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) demonstrated distinct a separation of the metabolome among the different treatment groups under Cd stress, indicating dynamic metabolic changes. Metabolic analysis suggested that genes involved are initially induced by Cd treatment, followed by the activation of the flavonoid biosynthesis pathway. This investigation provides new insights into the complex metabolic responses of C. maxima seedlings to Cd exposure.

Microplastics in soil affect the growth and physiological characteristics of Chinese fir and Phoebe bournei seedlings

Pot experiments were conducted using Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and Phoebe bournei (Hemsl.) Yang) to investigate whether soil microplastics adversely affect the nurturing and renewal of plantations. Microplastics composed of polyethylene and polypropylene with a size of 48 μm were used. The treatments included a control group (without microplastics) and groups treated with microplastic concentrations of 1% and 2% (w/w). The effects of microplastics on the growth, photosynthetic pigments in leaves, antioxidant systems, and osmotic regulation substances of the seedlings were analysed by measuring the seedling height, ground-line diameter growth, chlorophyll (chlorophyll a, chlorophyll b, and total chlorophyll) contents, antioxidant enzyme (superoxide dismutase, peroxidase, catalase) activities, and malondialdehyde, soluble sugar, and soluble protein levels. The results indicated that treatment with 1% polyethylene microplastics increased the chlorophyll a, total chlorophyll, and soluble protein contents in the leaves of both types of seedlings while inhibiting superoxide dismutase and peroxidase activities in P. bournei seedlings. Treatment with 2% polyethylene or polypropylene microplastics suppressed the chlorophyll a, chlorophyll b, and total chlorophyll contents; superoxide dismutase, peroxidase, and catalase activities; and soluble sugar and soluble protein levels in the leaves of both types of seedlings, resulting in reduced growth in terms of height and ground-line diameter. The physiological effects of polyethylene microplastics were more evident than those of polypropylene at the same concentration. The results demonstrated that microplastics can affect photosynthesis, the antioxidant system, and osmotic regulation in Chinese fir and P. bournei seedlings, thereby inhibiting their normal growth and development. Exposure to 1% (w/w) microplastics triggered stress responses in seedlings, whereas 2% (w/w) microplastics impeded seedling growth.

Zinc Oxide Nanoparticles: An Influential Element in Alleviating Salt Stress in Quinoa (Chenopodium quinoa L. Cv Atlas)

Climate change has intensified abiotic stresses, notably salinity, detrimentally affecting crop yield. To counter these effects, nanomaterials have emerged as a promising tool to mitigate the adverse impacts on plant growth and development. Specifically, zinc oxide nanoparticles (ZnO-NPs) have demonstrated efficacy in facilitating a gradual release of zinc, thus enhancing its bioavailability to plants. With the goal of ensuring sustainable plant production, our aim was to examine how green-synthesized ZnO-NPs influence the seedling growth of quinoa (Chenopodium quinoa L. Cv Atlas) under conditions of salinity stress. To induce salt stress, solutions with three different NaCl concentrations (0, 100, and 200 mM) were prepared. Additionally, Zn and ZnO-NPs were administered at four different concentrations (0, 50, 100, and 200 ppm). In this study, plant height (cm), plant weight (g), plant diameter (mm), chlorophyll content (SPAD), K/Na value, Ca/Na value, antioxidant enzyme activities (SOD: EU g−1 leaf; CAT: EU g−1 leaf; POD: EU g−1 leaf), H2O2 (mmol kg−1), MDA (nmol g−1 DW), proline (µg g−1 FW), and sucrose (g L−1), content parameters were measured. XRD analysis confirmed the crystalline structure of ZnO nanoparticles with identified planes. Salinity stress significantly reduced plant metrics and altered ion ratios, while increasing oxidative stress indicators and osmolytes. Conversely, Zn and ZnO-NPs mitigated these effects, reducing oxidative damage and enhancing enzyme activities. This supports Zn’s role in limiting salinity uptake and improving physiological responses in quinoa seedlings, suggesting a promising strategy for enhancing crop resilience. Overall, this study underscores nanomaterials’ potential in sustainable agriculture and stress management.

The Response of Ficus carica Seedlings to Foliar Spraying with α-Tocopherol and Organic Fertilization with SMC

The Response of Ficus carica Seedlings to Foliar Spraying with α-Tocopherol and Organic Fertilization with SMC

Response of Seedlings of Three Cultivars of Mandarin to Spraying and Addition of Nano-Fertilizer

Response of Seedlings of Three Cultivars of Mandarin to Spraying and Addition of Nano-Fertilizer

Application of Some Physical Seed Treatment Methods to Increase Germination of the Genus Catalpa Scop.

To increase the production volume of planting material for ornamental plants in the conditions of Central Kazakhstan, the selection of pre-sowing treatment methods for seed material becomes relevant. The use of safe and effective germination activators accelerates the biological processes of plant growth. The aim of the research was to study the impact of physical methods on the germination of Catalpa speciosa seeds as relatively safe methods of seed material activation. The seed treatment was carried out in three ways: the effect of laser irradiation, magnetic fields for 24, 72 hours, and twenty-four-hour aeration. A different response of seedlings to physical factors of influence was noted. The effect of the magnetic field allowed to increase germination by an average of 10 % compared to the control group. The impact of laser irradiation for 1‒4 minutes on the growth of Catalpa speciosa seedlings was less significant. Aeration had a positive effect on the energy of seed germination. Thus, to increase the germination of seedlings during early sowings of Catalpa speciosa seeds, it is promising to use the influence of the magnetic field and aeration.

Alteration in lipid metabolism is involved in nitrogen deficiency response in wheat seedlings

Changes of membrane lipid composition contribute to plant adaptation to various abiotic stresses. Here, a comparative study was undertaken to investigate the mechanisms of how lipid alteration affects plant growth and development under nitrogen (N) deficiency. Two wheat cultivars: the N deficiency-tolerant cultivar Xiaoyan 6 (XY) and the N deficiency-sensitive cultivar Aikang 58 (AK) were used to test if the high N-deficiency tolerance was related with lipid metabolism. The results showed that N deficiency inhibited the morpho-physiological parameters in both XY and AK cultivars, which showed a significant decrease in biomass, N content, photosynthetic efficiency, and lipid contents. However, these decreases were more pronounced in AK than XY. In addition, XY showed a notable increase in fatty acid unsaturation, relatively well-maintained chloroplast ultrastructure, and minimized damage of lipid peroxidation and enhanced PSII activity under N-deficient condition, as compared with AK. Transcription levels of many genes involved in lipid biosynthesis and fatty acid desaturation were up-regulated in response to N deficiency in two wheat cultivars, while the expressions were much higher in XY than AK under N deficiency. These results highlight the importance of alterations in lipid metabolism in N deficiency tolerance in wheat. High levels of lipid content and unsaturated fatty acids maintained the membrane structure and function, contributing to high photosynthesis and antioxidant capacities, thereby improved the tolerance to N deficiency.

Cadmium exposure on physiological responses of Erythrophleum fordii seedlings: A comparative study

The adaptability and tolerance of native species to heavy metal-contaminated soils can provide crucial insights for the development of effective heavy metal remediation strategies. Erythrophleum fordii (E. fordii) is a native hardwood species endemic to southern China that exhibits nitrogen fixation and soil improvement capabilities. This study examined the growth and physiological responses of E. fordii seedlings to varying cadmium (Cd) concentrations (control, Cd50, Cd100, Cd150, corresponding to 0, 50, 100, and 150 ppm), aimed to ascertain its potential role in phytoremediation efforts. Current results demonstrated that a moderate concentration of Cd (Cd50) significantly enhanced several plant characteristics, including plant height, root biomass, stem biomass, net photosynthetic rate, maximum net photosynthetic rate, and light saturation point. These observed improvements ranged from 12.15 % to 32.88 %, compared with control. Conversely, the highest Cd level (Cd150) resulted in substantial reductions in plant height, root biomass, chlorophyll content, and gas exchange parameters. Furthermore, malondialdehyde content increased markedly at Cd100 and Cd150 levels by 68.86 % and 118.92 %, respectively. The activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and the content of osmotic regulatory substances (soluble protein and soluble sugar) reached their peaks at Cd100 level, increased by 32.61–88.39 %. This indicated E. fordii's capacity to mitigate Cd-induced stress. Significant correlations were observed between growth indicators, chlorophyll content, and net photosynthetic rate, as well as between antioxidant enzymes and osmotic substances. The principal component analysis highlighted the superior performance of E. fordii in Cd50 treatment. The results revealed that moderate Cd promoted growth, photosynthetic activity, and physiological resilience in E. fordii, whereas the highest concentration of Cd (Cd150) was detrimental. These findings offer perceptiveness to the cultivation of E. fordii and its tolerance to heavy metals, with implications for the remediation of Cd-contaminated soils.

Understory bamboo removal impacts on woody seedling regeneration in forest ecosystems: a meta-analysis

BackgroundTree seedling regeneration in forests is often hindered by the competitive influence of dense understory bamboo competition. While localized studies have investigated the ecological effects of understory bamboo removal on tree seedlings, a comprehensive analysis at a global scale is lacking. In this meta-analysis, we synthesized 497 observations from 32 experimental studies to assess the overall effects of understory bamboo removal on tree seedling regeneration.ResultsThe results showed that understory bamboo removal enhanced tree seedling survival, emergence, and height growth. However, the response of tree seedlings to bamboo removal varied depending on regeneration characteristics, forest types, and bamboo removal methods. Specifically, understory bamboo removal increased the survival rate of deciduous seedlings but had no significant effect on evergreen seedlings. For regeneration stages, bamboo removal had a significant positive effect on the survival rate of saplings but not on seedlings. Regarding differences across forest types, bamboo removal significantly increased the emergence density of seedlings in deciduous broadleaf forests but had a significant negative influence in evergreen and mixed evergreen-deciduous forests. Additionally, natural removal of bamboo showed a greater positive effect on seedlings than bamboo removal by artificial or animal gnawing methods. Furthermore, we found that the duration of bamboo removal, mean annual temperature, precipitation of seasonality, and soil pH strongly influenced the response ratios of tree seedling regeneration.ConclusionsOur meta-analysis demonstrates the significant effects of understory bamboo removal on multiple facets of tree seedling dynamics across different regeneration characteristics, forest types, and bamboo removal methods. In addition, our study emphasizes that the duration of bamboo removal, climate, and soil pH have a critical effect on tree seedling regeneration. Our findings elucidate the effects of understory bamboo removal on seedling regeneration, offering robust scientific insights for sustainable forest management.

Interplant communication increases aphid resistance and alters rhizospheric microbes in neighboring plants of aphid-infested cucumbers.

Aphis gossypii Glover is a prevalent phytophagous insect that inflicts significant damage on cucumber plants. Recent studies have provided insights into plant communication and signal transduction within conspecifics. However, understanding of the effect of these communication mechanisms on adjacent cucumbers and their resident aphids, especially in the context of an aphid infestation, is still in its early stages. Utilizing a partitioned root configuration, a tendency for aphids to gather on nearby cucumber leaves of non-infested plants was observed. Furthermore, neighboring plants near aphid-infested cucumber plants showed a reduction in aphid reproduction rates. Concurrently, these plants exhibited a significant increase in reactive oxygen species (ROS) levels, along with enhanced defensive and antioxidant enzymatic responses. Analysis of the microbial community in the rhizosphere showed significant differences in species composition among the samples. Among these, the bacterial families Microbacteriaceae and Rhizobiaceae, along with the fungal species Leucocoprinus ianthinus and Mortierella globalpina, exhibited increases in their relative abundance in cucumber seedlings located near aphid-infested plants. Significantly, this study unveiled robust correlations between dominant microbial phyla and physiological indicators, primarily associated with aphid resistance mechanisms in plants. The results show that aphid-infested cucumber plants trigger oxidative stress responses in adjacent seedlings through complex interplant communication mechanisms. In addition, these plants cause changes in the composition of the rhizospheric microbial community and the physiological activity of neighboring plants, consequently boosting their natural resistance to aphids. This study provides essential theoretical foundations to guide the development of sustainable strategies for managing cucumber aphids. © 2024 Society of Chemical Industry.

Comparative RNA-seq analysis of Arabidopsis thaliana response to AtPep1 and flg22, reveals the identification of PP2-B13 and ACLP1 as new members in pattern-triggered immunity.

In this research, a high-throughput RNA sequencing-based transcriptome analysis technique (RNA-Seq) was used to evaluate differentially expressed genes (DEGs) in the wild type Arabidopsis seedlings in response to AtPep1, a well-known peptide representing an endogenous damage-associated molecular pattern (DAMP), and flg22, a well-known microbe-associated molecular pattern (MAMP). We compared and dissected the global transcriptional landscape of Arabidopsis thaliana in response to AtPep1 and flg22 and could identify shared and unique DEGs in response to these elicitors. We found that while a remarkable number of flg22 up-regulated genes were also induced by AtPep1, 256 genes were exclusively up-regulated in response to flg22, and 328 were exclusively up-regulated in response to AtPep1. Furthermore, among down-regulated DEGs upon flg22 treatment, 107 genes were exclusively down-regulated by flg22 treatment, while 411 genes were exclusively down-regulated by AtPep1. We found a number of hitherto overlooked genes to be induced upon treatment with either flg22 or with AtPep1, indicating their possible involvement general pathways in innate immunity. Here, we characterized two of them, namely PP2-B13 and ACLP1. pp2-b13 and aclp1 mutants showed increased susceptibility to infection by the virulent pathogen Pseudomonas syringae DC3000 and its mutant Pst DC3000 hrcC (lacking the type III secretion system), as evidenced by increased proliferation of the two pathogens in planta. Further, we present evidence that the aclp1 mutant is deficient in ethylene production upon flg22 treatment, while the pp2-b13 mutant is deficient in the production of reactive oxygen species (ROS). The results from this research provide new information for a better understanding of the immune system in Arabidopsis.

Exogenously applied putrescine regulates aluminium [al (III)] stress in maize (Zea mays L.): Physiological and metabolic implications

In this study, we investigated the role of exogenous application of putrescine (Put) for alleviation of Al (III) stress responses in maize seedlings. In presence of Put, the growth and biomass improved substantially in Al (III) stressed seedlings as compared to Al (III) alone. The production of hydrogen peroxide (H2O2) and superoxide radical (O2•-) were significantly restrained in during Al (III) stress in Put supplemented seedlings. The malondialdehyde (MDA) production was significantly controlled during Al (III) stress by Put supplementation as compared to the seedlings under Al (III) stress alone. The histochemical analysis showed variation in staining intensities of diaminobenzidine (DAB) and nitoroblue tetrazolium (NBT) salt to detect the presence of H2O2 and O2•- respectively, reflected strong role of Put in regulation of reactive oxygen species (ROS) production. The staining of roots with Schiff's reagent and Evans blue dye to detect lipid peroxidation and loss of plasma membrane integrity showed that Put controls the lipid peroxidation and maintains the integrity of the plasma membrane during Al (III) stress. The proton (1H) nuclear magnetic resonance (NMR) analysis of methanolic extracts of root and shoot of maize seedlings under Al (III) stress in presence or absence of Put showed considerable disparity in terms of metabolic profiles, which include amino acids, sugars, carbohydrates, organic acids and several aliphatic and aromatic compounds. The present study exhibited the potential role of Put for mitigation of Al (III) stress by enhancing growth, regulating ROS production, reducing oxidative stress, improving antioxidant metabolism and maintaining the metabolic pool.

Physiological and Proteome Analysis of the Effects of Chitosan Oligosaccharides on Salt Tolerance of Rice Seedlings.

Rice (Oryza sativa L.) is an important social-economic crop, and rice seedlings are easily affected by salt stress. Chitosan oligosaccharide (COS) plays a positive role in promoting plant growth and development. To gain a better understanding of the salt tolerance mechanism of rice under the action of COS, Nipponbare rice seedlings were selected as the experimental materials, and the physiological and biochemical indexes of rice seedlings in three stages (normal growth, salt stress and recovery) were measured. Unlabelled quantitative proteomics technology was used to study differential protein and signaling pathways of rice seedlings under salt stress, and the mechanism of COS to improve rice tolerance to salt stress was elucidated. Results showed that after treatment with COS, the chlorophyll content of rice seedlings was 1.26 times higher than that of the blank group (CK). The root activity during the recovery stage was 1.46 times that of the CK group. The soluble sugar in root, stem and leaf increased by 53.42%, 77.10% and 9.37%, respectively. The total amino acid content increased by 77% during the stem recovery stage. Furthermore, the malondialdehyde content in root, stem and leaf increased by 21.28%, 26.67% and 32.69%, respectively. The activity of oxide dismutase (SOD), peroxidase (POD) and oxygenase (CAT) were increased. There were more differentially expressed proteins in the three parts of the experimental group than in the CK group. Gene Ontology (GO) annotation of these differentially expressed proteins revealed that the experimental group was enriched for more entries. Then, through the Kyoto Encyclopedia of Genes and Genomes (KEGG), the top ten pathways enriched with differentially expressed proteins in the two groups (COS and CK groups) were utilized, and a detailed interpretation of the glycolysis and photosynthesis pathways was provided. Five key proteins, including phosphofructokinase, fructose bisphosphate aldolases, glycer-aldehyde-3-phosphate dehydrogenase, enolase and pyruvate kinase, were identified in the glycolysis pathway. In the photosynthesis pathway, oxygen evolution enhancement proteins, iron redox proteins and ferredoxin-NADPH reductase were the key proteins. The addition of COS led to an increase in the abundance of proteins, a response of rice seedlings to salt stress. COS helped rice seedlings resist salt stress. Furthermore, using COS as biopesticides and biofertilizers can effectively increase the utilization of saline-affected farmland, thereby contributing to the alleviating of the global food crisis.

Identification of RNAi-Related Genes and Transcriptome Assembly of Loblolly Pine (Pinus taeda, L.) Seedlings Exposed to Insect-Specific dsRNA

Considerable research has focused on gene silencing in tree-feeding insects, but how trees recognize and process double-stranded RNA (dsRNA) engineered to target plant pests is unknown. We performed transcriptomic assembly, preliminary differential expression analysis, and in silico annotation on loblolly pine (Pinus taeda, L.) seedlings exposed to southern pine beetle-specific dsRNA. This pilot study sought to elucidate the baseline response of seedlings challenged with insect-specific dsRNA. Treated and untreated seedlings were sequenced and following transcriptome assembly 20 RNAi-related proteins (RRPs) were annotated. Differential gene expression analysis conducted using DESeq2 followed by pathway enrichment revealed 7131 differentially expressed transcripts, of which 33% were upregulated and 67% were downregulated. Only two RRPs selected for analysis were upregulated in treated seedlings, showing a lack of detectable RNAi response with our methodology. Beyond RNAi-related proteins, pathway enrichment mapped to immune response systems and genetic and cellular processing. Upregulated transcripts included autophagy, amino sugar and nucleotide sugar metabolism, and plant hormone signal transduction. Downregulated transcripts included RNA degradation and fatty acid metabolism pathways. Multiple DICER-LIKE and ARGONAUTE proteins were also annotated in five other North American pines, revealing diversity among these crucial proteins. Understanding host plant response to RNAi-mediated pest control is essential to further develop this technology against tree pests.

Chilling stress response in tobacco seedlings: insights from transcriptome, proteome, and phosphoproteome analyses.

Tobacco (Nicotiana tabacum L.) is an important industrial crop, which is sensitive to chilling stress. Tobacco seedlings that have been subjected to chilling stress readily flower early, which seriously affects the yield and quality of their leaves. Currently, there has been progress in elucidating the molecular mechanisms by which tobacco responds to chilling stress. However, little is known about the phosphorylation that is mediated by chilling. In this study, the transcriptome, proteome and phosphoproteome were analyzed to elucidate the mechanisms of the responses of tobacco shoot and root to chilling stress (4 °C for 24 h). A total of 6,113 differentially expressed genes (DEGs), 153 differentially expressed proteins (DEPs) and 345 differential phosphopeptides were identified in the shoot, and the corresponding numbers in the root were 6,394, 212 and 404, respectively. This study showed that the tobacco seedlings to 24 h of chilling stress primarily responded to this phenomenon by altering their levels of phosphopeptide abundance. Kyoto Encyclopedia of Genes and Genomes analyses revealed that starch and sucrose metabolism and endocytosis were the common pathways in the shoot and root at these levels. In addition, the differential phosphopeptide corresponding proteins were also significantly enriched in the pathways of photosynthesis-antenna proteins and carbon fixation in photosynthetic organisms in the shoot and arginine and proline metabolism, peroxisome and RNA transport in the root. These results suggest that phosphoproteins in these pathways play important roles in the response to chilling stress. Moreover, kinases and transcription factors (TFs) that respond to chilling at the levels of phosphorylation are also crucial for resistance to chilling in tobacco seedlings. The phosphorylation or dephosphorylation of kinases, such as CDPKs and RLKs; and TFs, including VIP1-like, ABI5-like protein 2, TCP7-like, WRKY 6-like, MYC2-like and CAMTA7 among others, may play essential roles in the transduction of tobacco chilling signal and the transcriptional regulation of the genes that respond to chilling stress. Taken together, these findings provide new insights into the molecular mechanisms and regulatory networks of the responses of tobacco to chilling stress.

Exogenous application of 5-NGS increased osmotic stress resistance by improving leaf photosynthetic physiology and antioxidant capacity in maize.

Drought is a critical limiting factor affecting the growth and development of spring maize (Zea mays L.) seedlings in northeastern China. Sodium 5-nitroguaiacol (5-NGS) has been found to enhance plant cell metabolism and promote seedling growth, which may increase drought tolerance. In the present study, we investigated the response of maize seedlings to foliar application of a 5-NGS solution under osmotic stress induced by polyethylene glycol (PEG-6000). Four treatment groups were established: foliar application of distilled water (CK), foliar application of 5-NGS (NS), osmotic stress + foliar application of distilled water (D), and osmotic stress + foliar application of 5-NGS (DN). Plant characteristics including growth and photosynthetic and antioxidant capacities under the four treatments were evaluated. The results showed that under osmotic stress, the growth of maize seedlings was inhibited, and both the photosynthetic and antioxidant capacities were weakened. Additionally, there were significant increases in the proline and soluble sugar contents and a decrease in seedling relative water content (RWC). However, applying 5-NGS alleviated the impact of osmotic stress on maize seedling growth parameters, particularly the belowground biomass, with a dry mass change of less than 5% and increased relative water content (RWC). Moreover, treatment with 5-NGS mitigated the inhibition of photosynthesis caused by osmotic stress by restoring the net photosynthetic rate (Pn) through an increase in chlorophyll content, photosynthetic electron transport, and intercellular CO2 concentration (Ci). Furthermore, the activity of antioxidant enzymes in the aboveground parts recovered, resulting in an approximately 25% decrease in both malondialdehyde (MDA) and H2O2. Remarkably, the activity of enzymes in the underground parts exhibited more significant changes, with the contents of MDA and H2O2 decreasing by more than 50%. Finally, 5-NGS stimulated the dual roles of soluble sugars as osmoprotectants and energy sources for metabolism under osmotic stress, and the proline content increased by more than 30%. We found that 5-NGS played a role in the accumulation of photosynthates and the effective distribution of resources in maize seedlings. Based on these results, we determined that foliar application of 5-NGS may improve osmotic stress tolerance in maize seedlings. This study serves as a valuable reference for increasing maize yield under drought conditions.

Non-transcriptional regulatory activity of SMAX1 and SMXL2 mediates karrikin-regulated seedling response to red light in Arabidopsis

Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways. The transcriptional repressor proteins SUPPRESSOR OF MAX2 1 (SMAX1), SMAX1-like2 (SMXL2), and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or by inhibiting the activities of transcription factors. In this study, we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis. We discovered that SMAX1 and SMXL2 with mutations in their ethylene-response factor-associated amphiphilic repression (EAR) motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant. SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR 4 (PIF4) and PIF5 to enhance their protein stability by interacting with phytochrome B (phyB) and suppressing the association of phyB with PIF4 and PIF5. The karrikin-responsive genes were then identified by treatment with GR24ent−5DS, a GR24 analog showing karrikin activity. Interestingly, INDOLE-3-ACETIC ACID INDUCIBLE 29 (IAA29) expression was repressed by GR24ent−5DS treatment in a PIF4- and PIF5-dependent and EAR-independent manner, whereas KARRIKIN UPREGULATED F-BOX 1 (KUF1) expression was induced in a PIF4- and PIF5-independent and EAR-dependent manner. Furthermore, the non-transcriptional regulatory activity of SMAX1, which is independent of the EAR motif, had a global effect on gene expression. Taken together, these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.

Characterization of ascorbate-glutathione cycle response in Zostera marina seedlings under short-term temperature surge

The ascorbate-glutathione (AsA-GSH) cycle plays a critical role in scavenging hydrogen peroxide in plants and contributes significantly to plant stress tolerance. This study examines the cycle’s response in Zostera marina seedlings to warming, specifically under conditions of abnormal sea temperature increase. Three temperature gradients were established: 18°C (control group), 23°C (high-temperature group), and 28°C (abnormally high-temperature group). Results after 7 days of exposure to mild high temperature (23°C) showed decreased MDA content in the HT group, increased AsA/DHA ratio, and enhanced activity of enzymes related to the AsA-GSH cycle. However, exposure to extreme high temperatures resulted in increased oxidative damage and redox imbalance in the AHT group. Initially, enzymes associated with the AsA-GSH cycle, such as APX, MDHAR, GPX, and γ-ECS, increased but significantly decreased later under stress. In contrast, DHAR and GaILDH levels significantly rose on the seventh day. Transcriptome analysis revealed upregulation of APX, MDHAR, DHAR, GR, and γ-ECS genes in the HT group, with a decline in other enzyme gene expressions by the seventh day, except for APX. Under extreme high temperatures, APX expression was downregulated early in the stress period, while DHAR was upregulated, indicating Z. marina seedlings can mitigate oxidative damage under short-term high temperatures by activating the AsA-GSH cycle. Conversely, extreme high temperatures may inhibit this cycle, disrupt redox balance, and adversely affect Z. marina seedling establishment, potentially leading to their demise.