Dehydration-responsive Element-binding Protein Research Articles

TRANSCRIPTIONAL ANALYSIS OF SOYBEAN (Glycine max) GENES RELATED TO WATER DEFICIT

ABSTRACT The soybean crop has been gaining worldwide prominence, being widely disseminated due to its various forms of use in different segments. Genetic and environmental factors are decisive in the quality of this culture. A feature related to the environmental factor that has gained prominence is the water deficit. Molecular events are initiated by the perception of water stress, involving a complex genetic network. Studies in recent decades have already identified some genes related to water stress in plants, it is known that the dehydration-responsive element binding protein (DREB) plays an important role in the response to water deficit. Therefore, this work aimed to analyze the expression of genes related to water deficit in soybean. For the analysis of gene expression, leaves of soybean (Glycine max (L.) Merrill), cultivar M9144 RR, submitted to the following treatments were used: 25V25R – plants subjected to water deficit throughout the cycle, being irrigated with 25% of ETpc and 100V100R – plants that did not experience water deficit, being irrigated with 100% of ETpc throughout the cycle. The quantification of the relative expression of the genes GmDREB1 and GmDREB5 showed that the water stress suffered by the cultivar was greater in the reproductive stage. Keywords: Transcription factors, development stages, gene expression.

AtC3H3, an Arabidopsis Non-TZF Gene, Enhances Salt Tolerance by Increasing the Expression of Both ABA-Dependent and -Independent Stress-Responsive Genes.

Salinity causes widespread crop loss and prompts plants to adapt through changes in gene expression. In this study, we aimed to investigate the function of the non-tandem CCCH zinc-finger (non-TZF) protein gene AtC3H3 in response to salt stress in Arabidopsis. AtC3H3, a gene from the non-TZF gene family known for its RNA-binding and RNase activities, was up-regulated under osmotic stress, such as high salt and drought. When overexpressed in Arabidopsis, AtC3H3 improved tolerance to salt stress, but not drought stress. The expression of well-known abscisic acid (ABA)-dependent salt stress-responsive genes, namely Responsive to Desiccation 29B (RD29B), RD22, and Responsive to ABA 18 (RAB18), and representative ABA-independent salt stress-responsive genes, namely Dehydration-Responsive Element Binding protein 2A (DREB2A) and DREB2B, was significantly higher in AtC3H3-overexpressing transgenic plants (AtC3H3 OXs) than in wild-type plants (WT) under NaCl treatment, indicating its significance in both ABA-dependent and -independent signal transduction pathways. mRNA-sequencing (mRNA-Seq) analysis using NaCl-treated WT and AtC3H3 OXs revealed no potential target mRNAs for the RNase function of AtC3H3, suggesting that the potential targets of AtC3H3 might be noncoding RNAs and not mRNAs. Through this study, we conclusively demonstrated that AtC3H3 plays a crucial role in salt stress tolerance by influencing the expression of salt stress-responsive genes. These findings offer new insights into plant stress response mechanisms and suggest potential strategies for improving crop resilience to salinity stress.

Identification of DREB Family Genes in Banana and Their Function under Drought and Cold Stress.

Bananas are one of the most important cash crops in the tropics and subtropics. Drought and low-temperature stress affect the growth of banana. The DREB (dehydration responsive element binding protein) gene family, as one of the major transcription factor families, plays crucial roles in defense against abiotic stress. Currently, systematic analyses of the banana DREB (MaDREB) gene family have not yet been reported. In this study, 103 members of the MaDREB gene family were identified in the banana genome. In addition, transcriptomic analysis results revealed that MaDREBs responded to drought and cold stress. The expression of MaDREB14/22/51 was induced by drought and cold stress; these geneswere selected for further analysis. The qRT-PCR validation results confirmed the transcriptome results. Additionally, transgenic Arabidopsis plants overexpressing MaDREB14/22/51 exhibited enhanced resistance to drought and cold stress by reducing MDA content and increasing PRO and soluble sugar content. This study enhances our understanding of the function of the MaDREB gene family, provides new insights into their regulatory role under abiotic stress, and lays a good foundation for improving drought and cold stress-tolerant banana verities.

Characteristics of Rapeseed (Brassica rapa L.) genome DREB family demonstrate their roles in stress

Dehydration-responsive element-binding (DREB) proteins are crucial transcription factors in plant regulatory mechanisms, playing a key role in responding to environmental stresses. Dehydration-responsive element-binding (DREB) proteins are crucial transcription factors in plant regulatory mechanisms, playing a key role in responding to environmental stresses. This study employs bioinformatics research methods to identify and characterize the DREB gene family in rapeseed (Brassica rapa L.) under abiotic stress conditions. The approach facilitates a detailed exploration of the genomic architecture and potential regulatory mechanisms that these genes may exhibit in response to environmental stresses. A whole-genome survey identified 75 DREB genes in rapeseed, which were classified into six subgroups (Ⅰ-Ⅵ) based on phylogenetic comparison with Arabidopsis homologs. The amino acid lengths of these genes ranged from 144 to 530, with predicted molecular weights between 15.63 kDa and 60.36 kDa, and isoelectric points from 4.48 to 9.32. Chromosomal localization revealed that these genes are distributed across 10 chromosomes, predominantly near telomeric regions, with more than 10 DREB genes located on Chr3 and Chr9 respectively. Structural domain analysis indicated that 57 DREB genes possess a single exon. Promoter cis-element analyses suggested that BrDREB genes could respond to diverse stressors, including drought, heat, hormones, and light. Transcriptomic analysis under cold stress revealed significant upregulation of BrDREB17, 24, 49, 50, and 51 in response to low temperature, while five BrDREB genes were not expressed. Specifically, BrDREB17, 24, 49, 50, and 51 showed high expression levels at 3 h of cold stress, whereas BrDREB30, 42, and 67 were highly expressed at 24 h of cold stress. Gene Ontology (GO) analysis demonstrated that the majority of biological processes mediated by BrDREB are associated with plant stress resistance. Protein interaction network analysis revealed that BrDREB9 and BrDREB26 interact with 15 proteins each, underscoring their significant biological roles within the DREB family in rapeseed. These findings provide a theoretical framework for further examination of the physiological and biochemical properties of the DREB gene family components in rapeseed. Our results may help to screen candidate genes for cold resistance in rapeseed and select rapeseed varieties better suited to the Tibetan locality to improve quality and yield in agricultural production.

Isolation and characterization of three DREB-like genes encoding dehydration-responsive element binding proteins in chicory (Cichorium intybus)

Isolation and characterization of three DREB-like genes encoding dehydration-responsive element binding proteins in chicory (Cichorium intybus)

Transcription Cofactor CsMBF1c Enhances Heat Tolerance of Cucumber and Interacts with Heat-Related Proteins CsNFYA1 and CsDREB2.

Multiprotein bridging factor 1 (MBF1) is a very important transcription factor (TF) in plants, whose members influence numerous defense responses. Our study found that MBF1c in Cucurbitaceae was highly conserved. CsMBF1c expression was induced by temperature, salt stress, and abscisic acid (ABA) in cucumber. Overexpressed CsMBF1c enhanced the heat resistance of a cucumber, and the Csmbf1c mutant showed decreased resistance to high temperatures (HTs). CsMBF1c played an important role in stabilizing the photosynthetic system of cucumber under HT, and its expression was significantly associated with heat-related TFs and genes related to protein processing in the endoplasmic reticulum (ER). Protein interaction showed that CsMBF1c interacted with dehydration-responsive element binding protein 2 (CsDREB2) and nuclear factor Y A1 (CsNFYA1). Overexpression of CsNFYA1 in Arabidopsis improved the heat resistance. Transcriptional activation of CsNFYA1 was elevated by CsMBF1c. Therefore, CsMBF1c plays an important regulatory role in cucumber's resistance to high temperatures.

GA3 and BAP phytohormone seed priming enhances germination and PEG induced drought stress tolerance in soybean by triggering the expression of osmolytes, antioxidant enzymes and related genes at the early seedling growth stages

Drought stress strongly affects seed germination and seedling development during the early stages of plant growth in soybean (Glycine max L.). Seed priming with phytohormone (PH) is known to regulate various physiological and biochemical processes that govern plant growth and yield under optimal and stress conditions. In the present study, the effects of seed priming with Gibberellic acid (GA3) (0.28 mM), 6-Benzyl aminopurine (BAP) (20 mM) and Methyl Jasmonate (MJ) (2.5 mM) was studied during germination and at early seedling growth stages in JS-335 (drought sensitive) and MAUS-71 (moderately drought tolerant) soybean varieties under PFG induced drought stress conditions. The seed priming effects were studied in terms of germination percentage and rate (Timson Index), accumulation of osmolytes (proline and glycine betaine), antioxidant enzymes activity (superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)), and the relative expression of genes viz., Cu/Zn-superoxide dismutase copper chaperone (SOD-CCS) , iron-superoxide dismutase (SODB2) , betaine aldehyde dehydrogenase (BADH2) and dehydration-responsive element binding protein (DREB2A). The germination percentage of non-primed soybean seeds decreased under drought stress but significantly increased upon GA3 and BAP priming. Interestingly, seed priming with MJ completely inhibited the germination in both the varieties. GA3 and BAP seed priming increased proline and glycine betaine accumulation under PEG induced drought stress in both the soybean varieties. The results showed that the activities of SOD, APX and CAT were significantly enhanced in the leaves of seedlings raised from GA3 and BAP-primed seeds, as compared to the non-primed seeds under the drought stress conditions. Isozyme profiling of SOD and APX revealed that the GA3 and BAP seed priming treatments enhanced the drought-inducible expression of SOD isozymes rather than inducing novel isoforms. In case of APX isozymes, GA3 seed priming appears to preserve APX isozyme diversity in both varieties, and BAP seed priming elevated the expression of APX isoforms in both soybean varieties under the drought conditions. In response to the drought stress, relative expression of the genes associated with superoxide dismutase and glycine betaine viz., SOD CCS, SODB2, BADH2 and DREB2A was markedly upregulated in the leaves of seedlings raised from the GA3 and BAP primed seeds in both the soybean varieties. The global correlation analysis designated that the osmolyte Proline, antioxidant enzyme APX and CAT, and SOD CCS, SODB2, BADH2 and DREB2A genes were potent regulator for drought stress tolerance mechanism in soybean. This study illuminates the intricate interplay of GA3 and BAP hormonal seed priming during the germination and early seedling stages in soybean plants under the drought stress. This finding emphasizes the critical consideration of genotype specific reactions to the hormonal seed priming under PEG induced drought stress conditions.

Genome-wide identification and evolutionary analysis of the AP2/EREBP, COX and LTP genes in Zea mays L. under drought stress

AP2 (APETALA2)/EREBP (ethylene-responsive element-binding protein), cytochrome c oxidase (COX) and nonspecific lipid transfer proteins (LTP) play important roles in the response to drought stress. This is the first study to identify the COX gene in Zea mays L. via genome-wide analysis. The qRT‒PCR results indicated that AP2/EREBP, COX and LTP were downregulated, with fold changes of 0.84, 0.53 and 0.31, respectively, after 12 h of drought stress. Genome-wide analysis identified 78 AP2/EREBP, 6 COX and 10 LTP genes in Z. mays L. Domain analysis confirmed the presence of the AP2 domain, Cyt_c_Oxidase_Vb domain and nsLTP1 in the AP2/EREBP, COX and LTP proteins, respectively. The AP2/EREBP protein family (AP2) includes five different domain types: the AP2/ERF domain, the EREBP-like factor (EREBP), the ethylene responsive factor (ERF), the dehydration responsive element binding protein (DREB) and the SHN SHINE. Synteny analysis of the AP2/EREBP, COX and LTP genes revealed collinearity orthologous relationships in O. sativa, H. vulgare and A. thaliana. AP2/EREBP genes were found on the 10 chromosomes of Z. mays L. COX genes were found on chromosomes 1, 3, 4, 5, 7 and 8. LTP genes were found on chromosomes 1, 3, 6, 8, 9 and 10. In the present study, the Ka/Ks ratios of the AP2/EREBP paralogous pairs indicated that the AP2/EREBP genes were influenced primarily by purifying selection, which indicated that the AP2/EREBP genes received strong environmental pressure during evolution. The Ka/Ks ratios of the COX-3/COX-4 paralogous pairs indicate that the COX-3/COX-4 genes were influenced primarily by Darwinian selection (driving change). For the LTP genes, the Ka/Ks ratios of the LTP-1/LTP-10, LTP-5/LTP-3 and LTP-4/LTP-8 paralogous pairs indicate that these genes were influenced primarily by purifying selection, while the Ka/Ks ratios of the LTP-2/LTP-6 paralogous pairs indicate that these genes were influenced primarily by Darwinian selection. The duplication time of the AP2/EREBP paralogous gene pairs in Z. mays L. ranged from approximately 9.364 to 100.935 Mya. The duplication time of the COX-3/COX-4 paralogous gene pair was approximately 5.217 Mya. The duplication time of the LTP paralogous gene pairs ranged from approximately 19.064 to 96.477 Mya. The major focus of research is to identify the genes that are responsible for drought stress tolerance to improve maize for drought stress tolerance. The results of the present study will improve the understanding of the functions of the AP2/EREBP, COX and LTP genes in response to drought stress.

AnDREB5.1, a A5 group DREB gene from desert shrub Ammopiptanthus nanus, confers osmotic and cold stress tolerances in transgenic tobacco.

The Dehydration-Responsive Element Binding (DREB) subfamily of transcription factors plays crucial roles in plant abiotic stress response. Ammopiptanthus nanus (A. nanus) is an eremophyte exhibiting remarkable tolerance to environmental stress and DREB proteins may contribute to its tolerance to water deficit and low-temperature stress. In the present study, an A. nanus DREB A5 group transcription factor gene, AnDREB5.1, was isolated and characterized in terms of structure and function in abiotic stress tolerance. AnDREB5.1 protein is distributed in the nucleus, possesses transactivation capacity, and is capable of binding to DRE core cis-acting element. The transcription of AnDREB5.1 was induced under osmotic and cold stress. Tobacco seedlings overexpressing AnDREB5.1 displayed higher tolerance to cold stress, osmotic stress, and oxidative stress compared to wild-type tobacco (WT). Under osmotic and cold stress, overexpression of AnDREB5.1 increased antioxidant enzyme activity in tobacco leaves, inhibiting excessive elevation of ROS levels. Transcriptome sequencing analysis showed that overexpression of AnDREB5.1 raised the tolerance of transgenic tobacco seedlings to abiotic stress by regulating multiple genes, including antioxidant enzymes, transcription factors, and stress-tolerant related functional genes like NtCOR413 and NtLEA14. This study provides new evidence for understanding the potential roles of the DREB A5 subgroup members in plants.

Screening cotton genotypes for their drought tolerance ability based on the expression level of dehydration-responsive element-binding protein and proline biosynthesis-related genes and morpho-physio-biochemical responses.

Drought stress adversely affects growth, development, productivity, and fiber quality of cotton (Gossypium hirsutum L). Breeding strategies to enhance drought tolerance require an improved knowledge of plant drought responses necessitating proper identification of drought-tolerant genotypes of crops, including cotton. The objective of this study was to classify the selected cotton genotypes for their drought tolerance ability based on morpho-physio-biochemical traits using Hierarchical Ward's cluster analysis. Five genotypes of cotton (Takfa 3, Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5) were selected as plant materials, and were grown under well-watered (WW; 98 ± 2% field capacity) and water-deficit (WD; 50 ± 2% field capacity) conditions for 16days during the flower initiation stage. Data on morpho-physio-biochemical parameters and gene expression levels for these parameters were collected, and subsequently genotypes were classified either as a drought tolerant or drought susceptible one. Upregulation of GhPRP (proline-rich protein), GhP5CS (Δ1-pyrroline-5-carboxylate synthetase), and GhP5CR (Δ1-pyrroline-5-carboxylate reductase) in relation to free proline enrichment was observed in Takfa 3 genotype under WD condition. An accumulation of free proline, total soluble sugar, and potassium in plants under WD conditions was detected, which played a key role as major osmolytes controlling cellular osmotic potential. Magnesium and calcium concentrations were also enriched in leaves under WD conditions, functioning as essential elements and regulating photosynthetic abilities. Leaf greenness, net photosynthetic rate, stomatal conductance, and transpiration rate were also declined under WD conditions, leading to growth retardation, especially aboveground traits of Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5 genotypes. An increase in leaf temperature (1.1 - 4.0°C) and crop water stress index (CWSI > 0.75) in relation to stomatal closure and reduced transpiration rate was recorded in cotton genotypes under WD conditions compared with WW conditions. Based on the increase of free proline, soluble sugar, leaf temperature, and CWSI, as well as the decrease of aboveground growth traits and physiological attributes, five genotypes were categorized into two cluster groups: drought tolerant (Takfa 3) and drought susceptible (Takfa 6, Takfa 7, Takfa 84-4, and Takfa 86-5). The identified drought-tolerant cotton genotype, namely, Takfa 3, may be grown in areas experiencing drought conditions. It is recommended to further validate the yield traits of Takfa 3 under rainfed field conditions in drought-prone environments.

Picea wilsonii NAC31 and DREB2A Cooperatively Activate ERD1 to Modulate Drought Resistance in Transgenic Arabidopsis.

The NAC family of transcription factors (TFs) regulate plant development and abiotic stress. However, the specific function and response mechanism of NAC TFs that increase drought resistance in Picea wilsonii remain largely unknown. In this study, we functionally characterized a member of the PwNAC family known as PwNAC31. PwNAC31 is a nuclear-localized protein with transcriptional activation activity and contains an NAC domain that shows extensive homology with ANAC072 in Arabidopsis. The expression level of PwNAC31 is significantly upregulated under drought and ABA treatments. The heterologous expression of PwNAC31 in atnac072 Arabidopsis mutants enhances the seed vigor and germination rates and restores the hypersensitive phenotype of atnac072 under drought stress, accompanied by the up-regulated expression of drought-responsive genes such as DREB2A (DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2A) and ERD1 (EARLY RESPONSIVE TO DEHYDRATION STRESS 1). Yeast two-hybrid and bimolecular fluorescence complementation assays confirmed that PwNAC31 interacts with DREB2A and ABF3 (ABSCISIC ACID-RESPONSIVE ELEMENT-BINDING FACTOR 3). Yeast one-hybrid and dual-luciferase assays showed that PwNAC31, together with its interaction protein DREB2A, directly regulated the expression of ERD1 by binding to the DRE element of the ERD1 promoter. Collectively, our study provides evidence that PwNAC31 activates ERD1 by interacting with DREB2A to enhance drought tolerance in transgenic Arabidopsis.

Reference genes for Eucalyptus spp. under Beauveria bassiana inoculation and subsequently infestation by the galling wasp Leptocybe invasa

Relative gene expression analysis through RT-qPCR is an important molecular technique that helps understanding different molecular mechanisms, such as the plant defense response to insect pests. However, the use of RT-qPCR for gene expression analysis can be affected by factors that directly affect the reliability of the results. Among these factors, the appropriate choice of reference genes is crucial and can strongly impact RT-qPCR relative gene expression analyses, highlighting the importance in correctly choosing the most suitable genes for the success of the analysis. Thus, this study aimed to select and validate reference genes for relative gene expression studies through RT-qPCR in hybrids of Eucalyptus tereticornis × Eucalyptus camaldulensis (drought tolerant and susceptible to Leptocybe invasa) under conditions of inoculation by the Beauveria bassiana fungus and subsequent infestation by L. invasa. The expression level and stability of eleven candidate genes were evaluated. Stability was analyzed using the RefFinder tool, which integrates the geNorm, NormFinder, BestKeeper, and Delta-Ct algorithms. The selected reference genes were validated through the expression analysis of the transcriptional factor EcDREB2 (dehydration-responsive element-binding protein 2). For all treatments evaluated, EcPTB, EcPP2A-1, and EcEUC12 were the best reference genes. The triplets EcPTB/EcEUC12/EcUBP6, EcPP2A-1/EcEUC12/EcPTB, EcIDH/EcSAND/Ecα-TUB, EcPP2A-1/Ecα-TUB/EcPTB, and EcPP2A-1/EcUPL7/EcSAND were the best reference genes for the control plants, mother plants, plants inoculated with B. bassiana, plants infested with L. invasa, and plants inoculated with B. bassiana and subsequently infested with L. invasa, respectively. The best determined reference genes were used to normalize the RT-qPCR expression data for each experimental condition evaluated. The results emphasize the importance of this type of study to ensure the reliability of relative gene expression analyses. Furthermore, the findings of this study can be used as a basis for future research, comprising gene expression analysis of different eucalyptus metabolic pathways.

Phytosulfokine promotes fruit ripening and quality via phosphorylation of transcription factor DREB2F in tomato.

Phytosulfokine (PSK), a plant peptide hormone with a wide range of biological functions, is recognized by its receptor PHYTOSULFOKINE RECEPTOR 1 (PSKR1). Previous studies have reported that PSK plays important roles in plant growth, development, and stress responses. However, the involvement of PSK in fruit development and quality formation remains largely unknown. Here, using tomato (Solanum lycopersicum) as a research model, we show that exogenous application of PSK promotes the initiation of fruit ripening and quality formation, while these processes are delayed in pskr1 mutant fruits. Transcriptomic profiling revealed that molecular events and metabolic pathways associated with fruit ripening and quality formation are affected in pskr1 mutant lines and transcription factors are involved in PSKR1-mediated ripening. Yeast screening further identified that DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2F (DREB2F) interacts with PSKR1. Silencing of DREB2F delayed the initiation of fruit ripening and inhibited the promoting effect of PSK on fruit ripening. Moreover, the interaction between PSKR1 and DREB2F led to phosphorylation of DREB2F. PSK improved the efficiency of DREB2F phosphorylation by PSKR1 at the tyrosine-30 site, and the phosphorylation of this site increased the transcription level of potential target genes related to the ripening process and functioned in promoting fruit ripening and quality formation. These findings shed light on the involvement of PSK and its downstream signaling molecule DREB2F in controlling climacteric fruit ripening, offering insights into the regulatory mechanisms governing ripening processes in fleshy fruits.

The silicon regulates microbiome diversity and plant defenses during cold stress in Glycine max L.

With climate change, frequent exposure of bioenergy and food crops, specifically soybean (Glycine max L.), to low-temperature episodes is a major obstacle in maintaining sustainable plant growth at early growth stages. Silicon (Si) is a quasi-essential nutrient that can help to improve stress tolerance; however, how Si and a combination of cold stress episodes influence plant growth, plant physiology, and microbiome diversity has yet to be fully discovered. The soybean plants were exposed to cold stress (8-10°C) with or without applying Si, and the different plant organs (shoot and root) and rhizospheric soil were subjected to microbiome analysis. The plant growth, physiology, and gene expression analysis of plant defenses during stress and Si were investigated. We showed that cold stress significantly retarded soybean plants' growth and biomass, whereas, Si-treated plants showed ameliorated negative impacts on plant growth at early seedling stages. The beneficial effects of Si were also evident from significantly reduced antioxidant activities - suggesting lower cold-induced oxidative stress. Interestingly, Si also downregulated critical genes of the abscisic acid pathway and osmotic regulation (9-cis-epoxy carotenoid dioxygenase and dehydration-responsive element binding protein) during cold stress. Si positively influenced alpha and beta diversities of bacterial and fungal microbiomes with or without cold stress. Results showed significant variation in microbiome composition in the rhizosphere (root and soil) and phyllosphere (shoot) in Si-treated plants with or without cold stress exposures. Among microbiome phyla, Proteobacteria, Bacteroidota, and Ascomycota were significantly more abundant in Si treatments in cold stress than in control conditions. For the core microbiome, we identified 179 taxa, including 88 unique bacterial genera in which Edaphobacter, Haliangium, and Streptomyces were highly abundant. Enhanced extracellular enzyme activities in the cold and Si+cold treatments, specifically phosphatase and glucosidases, also reflected the microbiome abundance. In conclusion, this work elucidates cold-mediated changes in microbiome diversity and plant growth, including the positive impact Si can have on cold tolerance at early soybean growth stages - a step toward understanding crop productivity and stress tolerance.

NFXL1 functions as a transcriptional activator required for thermotolerance at reproductive stage in Arabidopsis.

Plants are highly susceptible to abiotic stresses, particularly heat stress during the reproductive stage. However, the specific molecular mechanisms underlying this sensitivity remain largely unknown. In the current study, we demonstrate that the Nuclear Transcription Factor, X-box Binding Protein 1-Like 1 (NFXL1), directly regulates the expression of DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2A (DREB2A), which is crucial for reproductive thermotolerance in Arabidopsis. NFXL1 is upregulated by heat stress, and its mutation leads to a reduction in silique length (seed number) under heat stress conditions. RNA-Seq analysis reveals that NFXL1 has a global impact on the expression of heat stress responsive genes, including DREB2A, Heat Shock Factor A3 (HSFA3) and Heat Shock Protein 17.6 (HSP17.6) in flower buds. Interestingly, NFXL1 is enriched in the promoter region of DREB2A, but not of either HSFA3 or HSP17.6. Further experiments using electrophoretic mobility shift assay have confirmed that NFXL1 directly binds to the DNA fragment derived from the DREB2A promoter. Moreover, effector-reporter assays have shown that NFXL1 activates the DREB2A promoter. The DREB2A mutants are also heat stress sensitive at the reproductive stage, and DEREB2A is epistatic to NFXL1 in regulating thermotolerance in flower buds. It is known that HSFA3, a direct target of DREB2A, regulates the expression of heat shock proteins genes under heat stress conditions. Thus, our findings establish NFXL1 as a critical upstream regulator of DREB2A in the transcriptional cassette responsible for heat stress responses required for reproductive thermotolerance in Arabidopsis.

Molecular identification of twenty NtDREB homologs and overexpression of NtDREB_A2.1 improved plant growth in response to cold-stress and P-nutrition limitation

Being as a useful model plant for biological study and significant industrial-crop that is sensitive to low temperature, tobacco is frequently adopted to evaluate functions of interested genes from other species by heterologous expression. Dehydration-responsive element binding (DREB) proteins are a type of transcription factors involved in plant responses to abiotic/biotic stimuli. However, genetic information and molecular-physiological roles of tobacco DREBs are little described. Here, we identified 20 NtDREBs containing a typical AP2-domain and phylogenetically classified them into five subgroups (A2-A6). Inspecting promoter sequences of NtDREBs revealed a different enrichment of certain abiotic stress-related cis-elements including ‘MeJA- and ABA-responsive and A/T-rich binding’ components. Analysis of publicly available RNA-seq data showed that many NtDREBs were transcriptionally regulated by cold-treatment. Furthermore, we assessed physiological roles in tobacco of NtDREB_A2.1, because of its rapid and/or strong expression responsive to low temperature and plant P- and N-nutritional status. Overexpression of NtDREB2.1 in tobacco cultivated under 15 °C improved the growth with increased plant-height and leaf-area compared to WT. Interestingly, NtDREB_2A.1 overexpression negatively influenced plant growth under conditions of low/high N-supply and 15 °C, whereas NtDREB_2A.1-transgenic lines could effectively utilize external low- and/or high P for better growth with increased N- and P-accumulation under 15–25 °C. Our work added not only new members to the DREB-subfamily but a valuable molecular-target for engineering of crops, aiming at improvement of plant cold-tolerance and utilization of soil phosphorus occurring at low available levels for plants in most soils.

Life-Cycle Multiomics ofRice Shoots Reveals Growth Stage-Specific Effects ofDrought Stress andTime-Lag Drought Responses.

Field-grown rice plants are exposed to various stresses at different stages of their life cycle, but little is known about the effects of stage-specific stresses on phenomes and transcriptomes. In this study, we performed integrated time-course multiomics on rice at 3-d intervals from seedling to heading stage under six drought conditions in a well-controlled growth chamber. Drought stress at seedling and reproductive stages reduced yield performance by reducing seed number and setting rate, respectively. High temporal resolution analysis revealed that drought response occurred in two steps: a rapid response via the abscisic acid (ABA) signaling pathway and a slightly delayed DEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN (DREB) pathway, allowing plants to respond flexibly to deteriorating soil water conditions. Our long-term time-course multiomics showed that temporary drought stress delayed flowering due to prolonged expression of the flowering repressor gene GRAIN NUMBER, PLANT HEIGHT AND HEADING DATE 7 (Ghd7) and delayed expression of the florigen genes HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1). Our life-cycle multiomics dataset on rice shoots under drought conditions provides a valuable resource for further functional genomic studies to improve crop resilience to drought stress.

The Knockdown of AUXIN RESPONSE FACTOR 2 Confers Enhanced Tolerance to Salt and Drought Stresses in Tomato (Solanum lycopersicum L.).

Auxin response factors (ARFs) act as key elements of the auxin-signaling pathway and play important roles in the process of a plant's growth, development, and response to environmental conditions. We studied the implication of the SlARF2 gene in the tomato response to salt (150 mM of NaCl) and drought (15% PEG 20000) stresses. The functional characterization of SlARF2 knockdown tomato mutants revealed that the downregulation of this gene enhanced primary root length and root branching and reduced plant wilting. At the physiological level, the arf2 mutant line displayed higher chlorophyll, soluble sugars, proline, and relative water contents as well as lower stomatal conductance and a decreased malondialdehyde content. Moreover, SlARF2 knockdown tomato mutants demonstrated higher activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) under salt and drought stresses than the wild type. Indeed, the stress tolerance of the arf2 mutant was also reflected by the upregulation of stress-related genes involved in ROS scavenging and plant defense, including SOD, CAT, dehydration-responsive element-binding protein, and early responsive to dehydration, which can ultimately result in a better resistance to salt and drought stresses. Furthermore, the transcriptional levels of the Δ1-pyrroline-5-carboxylate synthase (P5CS) gene were upregulated in the arf2 mutant after stress, in correlation with the higher levels of proline. Taken together, our findings reveal that SlARF2 is implicated in salt and drought tolerance in tomato and provides some considerable elements for improving the abiotic stress tolerance and increasing the crop yields of tomato.

Tea-based biochar-mediated changes in cation diffusion homeostasis in rice grown in heavy metal (loid) contaminated mining soil

Foreseeable future scenarios highlight the urgency of applying eco-safe avoidance methods or tolerance to heavy metal(loid) (HM) stress in agricultural production areas of contamination. The analyses show that the Ni, Mn, As, and Cr concentrations detected in the soils of the paddy fields in the Black Sea region vary between 123.60 and 263.30; 687–1271; 8.90–14.50; 162.00–340.00 mg kg−1 proving high accumulation of Ni, Mn, As, Cr in rice. Overconsumption of rice farmed extensively on these soils might also lead to human HM-related health problems. Therefore, in the current study, the approach of using tea-based biochar (BC) proven to have one of the most significant potentials as a soil amendment to reduce HM transmission to in-vitro-grown rice plants was investigated in the soil medium naturally contaminated with HMs. The tea-BC was produced from readily available local black tea waste of a conventional fermentation process and applied in the in-vitro experiments. Among the tested doses examined, 1% tea-BC showed a more positive effect on rice plant growth and development characterized by a better relative growth rate (59.7 and 84 mg g−1 d−1 for root and shoot tissues), photosynthetic pigment intactness (62.48 μg mL−1), cellular membrane integrity (93%), and relative water (96%) than the other rates (0% BC, 3%BC, 5%BC). The mRNA expression data highlights the probability of a cation diffusion facilitator (CDF) (OsMTP11) in concert with catalase isozyme (CATa) and dehydration-responsive element binding protein (DREB1a) linking the HM detoxification, oxidative defense, and dehydration pathways with the help of tea-BC. At the optimum concentration (1%BC), this approach might reduce HM accumulation levels of crops planted in HM-contaminated farmlands.

Overexpression of an autophagy-related gene DiATG3 from Davidia involucrata improves plant thermotolerance by enhancing the accumulation of polyamines and regulating genes in calcium and MAPK signaling pathways

Autophagy, a conserved eukaryotic mechanism for degrading intracellular constituents, plays prominent roles in plant abiotic stress tolerance. This study aimed to isolate an autophagy-related gene DiATG3 from a cool-adapted endangered plant species, dove tree (Davidia involucrata Baill.), and to investigate the physiological functions and regulatory mechanisms of DiATG3 for improving heat tolerance. DiATG3 was found to mainly localize to cytoplasm and possess the N-terminal domain, the catalytic domain with the HPC motif, and the C-terminal domain with the FLKF motif. Elevated transcript level of DiATG3 was detected in D. involucrata treated with heat stress. The constitutive overexpression of DiATG3 in Arabidopsis led to elevated levels of autophagy and conferred tolerance under heat stress. Furthermore, this thermotolerant phenotype was associated with improved photosynthetic capacity, higher antioxidant enzyme activities, and increased accumulation of polyamines. Transcriptome analysis suggest that activated calcium signaling and mitogen-activated protein kinase (MAPK) cascade may act as a central hub necessary for DiATG3-mediated heat tolerance. In addition, DiATG3 overexpression resulted in up-regulated expression of stress-related genes including heat shock factor A3 (AtHSFA3), dehydration-responsive element-binding protein 2C (AtDREB2C), AtWRKY26, and AtWRKY33 after heat treatment. Our study could yield insights into the engagement of plant autophagy during abiotic stress responses and contribute to breeding and engineering thermotolerant endangered plant species.