Pivotal role of the AREB/ABF-SnRK2 pathway in ABRE-mediated transcription in response to osmotic stress in plants

Genome-wide exploration: Evolution, structural characterization, molecular docking, molecular dynamics simulation and expression analysis of sugar transporter (ST) gene family in potato (Solanum tuberosum)

Sugars are the basic structural components of carbohydrates. Sugar transport is crucial for plants to ensure their optimal growth and development. Long-distance sugar transport occurs through either diffusion-based passive or active transport mediated by transporter proteins. In potatoes, STs play a vital role in sugar transport and total sugar accumulation. To better understand the roles of these transporters, in-depth structural, protein characterization, and tissue-specific expression analysis were performed. A total of 61 StSTs were identified and classified into eight sub-families (STP, PLT, ERD6L, INT, TMT, pGlcT, SUC, and VGT). The majority of StSTs were found in the plasma membrane, and all of them were dispersed throughout the 12 chromosomes. Exon and motif counts ranged from 1-18 and 1-10, respectively. In synteny analysis with four plant genomes, the highest (38) orthologous gene pair was found with S. lycopersicum (tomato). In 3D protein modeling, the alpha helix and transmembrane helices range varied from 32 % to 78 % and 53 %-57 %, respectively. During molecular docking analysis, the lowest binding energy was observed for Glu-StINT1 (ΔG: - 6.6 kcal/mol), Fru-StVGT1 (ΔG: - 6.1 kcal/mol), Gal-StSTP10 (ΔG: - 6.5 kcal/mol), and Suc-StINT2 (ΔG: - 7.5 kcal/mol), among 244 docking results. These complexes showed significant hydrogen and hydrophobic interactions, due to having significant amino acid residues. The molecular dynamics (MD) simulation of four complexes (Glu-StINT1, Fru-StVGT1, Gal-StSTP10, and Suc-StINT2) validated the ligand's stable attachment to the intended target proteins and it can be predicted that these complexes are the best sugar transporters of potato. In RNA-seq mediated expression analysis, StSTP12, StERD6L-6, 12, StpGlcT3, StVGT1, and StVGT2, were significantly upregulated in vegetative tissues/organs, revealing their significant role in vegetative organ development. In addition, stu-miRNA395 was the largest family interacting with StERD6L-1 and StTMT2 genes, demonstrating their significant role in sulfate metabolism. The detection and visualization of potential transcription factors (TFs) like ERF, Dof, MYB, BBR-BPC, LBD, and NAC in conjunction with the StSTs gene indicate their significant contribution to stress tolerance and DNA conversion and transcription into RNA. A significant interaction of StSTs in the PPI network might be due to their cumulative role in the same signaling pathways. The integration of these findings will guide the development of programming-based sugar transporter-mediated genetic circuits to improve the sugar accumulation in potatoes using synthetic biology approaches.

Mapping the molecular signature of ABA-regulated gene expression in germinating barley embryos

BACKGROUND

Abscisic acid (ABA) regulates key plant processes, including seed germination, dormancy, and abiotic stress responses. While its physiological role in germination is well-documented, the molecular mechanisms are still poorly understood. To address this, we analyzed transcriptomic and metabolomic changes in ABA-treated germinating barley (Hordeum vulgare) embryos. To map ABA-responsive gene expression across embryonic tissues, we employed the Visium Spatial Transcriptomics (10× Genomics). This approach, which remains technically challenging to be applied in plant tissues, enabled the precise localization of gene expression across six embryo regions, offering insights into tissue-specific expression patterns that cannot be resolved by traditional RNA-seq.

RESULTS

Transcriptomic analysis indicated that ABA acts primarily as a germination repressor. Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses linked ABA-inhibited genes to energy metabolism, lignin biosynthesis, cell wall organization, and photosynthesis, while induced genes were associated with environmental adaptation and phytohormone signaling. Differentially expressed genes (DEGs) correlated with metabolites involved in phytohormone pathways, including gibberellins, jasmonates, brassinosteroids, salicylic acid, auxins, and ABA metabolism. Comparisons with developing seed transcriptomes suggested an ABA-associated gene expression signature in embryos. Spatial transcriptomics technique made possible the precise identification of ABA-induced transcriptional changes within distinct embryonic tissues.

CONCLUSIONS

Integrating transcriptomics, metabolomics and spatial transcriptomics defined the molecular signature of ABA-induced modulation of phytohormonal crosstalk, energy metabolism, and tissue-specific gene activity in germinating seeds. The successful use of spatial transcriptomics adds a novel layer of resolution for understanding tissue-specific ABA responses during barley seed germination. These findings offer new insights into the ABA role in seed germination and potential strategies for enhancing crop resilience.

TaPP2C-a5 fine-tunes wheat seed dormancy and germination with a Triticeae-specific, alternatively spliced transcript

INTRODUCTION

The sessile plants often experience environmental conditions not ideal for growth, and therefore have evolved strategies to survive and adapt to stress conditions. Abscisic acid (ABA) regulates plant development and abiotic stress response. Clade A type 2C protein phosphatases (PP2Cs), act as co-receptors of ABA, negatively regulate ABA signalling. However, the biological function and detailed molecular mechanism of clade A PP2Cs in ABA signalling pathway remain to be elucidated in wheat.

OBJECTIVES

To analyze the mechanisms of stress response and development mediated by ABA signal precisely regulated by TaPP2C-a5 at the post-transcriptional level in wheat, providing candidate genes for wheat improvement.

METHODS

Based on our previous results of TaPP2Cs gene family analysis, the function and detailed regulation mechanisms of TaPP2C-a5 gene in seed dormancy and germination as well as drought response mediated by ABA signaling pathway were explored through reverse genetics technology.

RESULTS

We found that class A TaPP2C-a5 underwent alternative splicing (AS) to produce two transcripts encoding TaPP2C-a5.1 and TaPP2C-a5.2, respectively. Both TaPP2C-a5.1 and TaPP2C-a5.2 were highly expressed in mature seeds, and were upregulated by exogenous ABA in seedlings. Overexpression of TaPP2C-a5.1 and TaPP2C-a5.2 coordinately negatively regulated seed dormancy and ABA-mediated seed germination as well as post-germination developmental arrest in wheat. TaPP2C-a5.1 negatively regulated drought stress response, while TaPP2C-a5.2 did not participate in drought stress response. The homologous genes of TaPP2C-a5 underwent the same AS as TaPP2C-a5 in tetraploid wheat, but not in rice.

CONCLUSION

Our results revealed that TaPP2C-a5 gene underwent AS and was involved in the regulation of seed dormancy and germination, as well as drought stress response mediated by the ABA signaling at the post-transcriptional level. Our work not only provide a potential target gene to improve PHS resistance, but also emphasize alternative splicing as a strategy with evolution contexts to fine-tune ABA signaling and its involvement in certain biological process.

Functional analysis of open stomata 1-slow anion channel associated 1-6 protein module in enhancing drought tolerance in tomato through stomatal regulation mechanisms

Tomato (Solanum lycopersicum) is an important vegetable crop, whose growth and development are frequently subjected to drought stress, which severely limits its growth and yield. Identifying key drought-resistance genes in tomato is crucial for elucidating the mechanisms of drought resistance and improving tomato's drought tolerance, which has practical implications for agricultural production. The results of this study demonstrate that silencing SlSLAC1-6 (Slow anion channel associated 1-6) reduces tomato's drought tolerance. SnRK2.6/OST1 (Open stomata 1) protein kinase is a key component in plants' resistance to abiotic stress. Interactions between SlOST1 and SlSLAC1-6 were confirmed through Y2H, BiFC, LCI, Co-IP, and Pull-down assays. Simultaneously, overexpression and knockout of SlOST1 proved that it positively regulates tomato's drought tolerance by influencing reactive oxygen species (ROS) homeostasis, photosynthetic capacity, stomatal closure, and other mechanisms. Silencing SlSLAC1-6 in SlOST1 knockout plants further reduced tomato's drought tolerance. The regulation of tomato drought tolerance by SlOST1 and SlSLAC1-6 highlights the complexity of plant adaptation to drought. These findings provide new insights into the regulatory network of the SlOST1-SlSLAC1 protein module in tomato drought tolerance and offer gene resources for future tomato drought-resistance breeding.

Identification of the maize drought-resistant gene Zinc-finger Inflorescence Meristem 23 through high-resolution temporal transcriptome analysis

Drought is a major abiotic stress that significantly limits maize productivity. However, previous transcriptomic studies with limited time-point sampling have hindered the construction of robust co-expression networks, making it challenging to identify reliable hub genes involved in drought tolerance. To overcome this limitation, we generated a high-temporal-resolution transcriptome dataset spanning 108 time points from maize seedlings subjected to two consecutive rounds of drought and re-watering treatments. A total of 8477 drought-responsive genes (DRGs) were identified by comparing drought-stressed and well-watered controls. Using weighted gene co-expression network analysis (WGCNA), we constructed 17 co-expression modules, of which 8 were strongly associated with drought stress responses and collectively contained 353 hub genes. Among them, we validated the drought resistance functions of ZmCPK35, a known drought-responsive gene, and Zinc-finger Inflorescence Meristem 23 (ZmZIM23), a newly identified drought-regulatory gene, within the M10 module. Functional analysis revealed that ZmZIM23 enhances drought tolerance by improving water-use efficiency, reducing transpiration rates, and promoting biomass accumulation. Furthermore, yeast one-hybrid (Y1H) and dual-luciferase (LUC) assays demonstrated that ZmWRKY40, another M10 module member, transcriptionally regulates both ZmZIM23 and ZmCPK35. By integrating high-resolution transcriptomic data with co-expression network analyses, this study unveils key drought-responsive regulatory networks in maize and identifies novel candidate genes for improving drought tolerance. These findings provide valuable insights into the genetic foundation of drought adaptation and offer potential targets for the development of drought-resistant maize cultivars.

SnRK2s: Kinases or Substrates?

Throughout their life cycle, plants persistent through environmental adversities that activate sophisticated stress-signaling networks, with protein kinases serving as pivotal regulators of these responses. The sucrose non-fermenting-1-related protein kinase 2 (SnRK2), a plant-specific serine/threonine kinase, orchestrates stress adaptation by phosphorylating downstream targets to modulate gene expression and physiological adjustments. While SnRK2 substrates have been extensively identified, the existing literature lacks a systematic classification of these components and their functional implications. This review synthesizes recent advances in characterizing SnRK2-phosphorylated substrates in Arabidopsis thaliana, providing a mechanistic framework for their roles in stress signaling and developmental regulation. Furthermore, we explore the understudied paradigm of SnRK2 undergoing multilayered post-translational modifications (PTMs), including phosphorylation, ubiquitination, SUMOylation, S-nitrosylation, sulfation (S-sulfination and tyrosine sulfation), and N-glycosylation. These PTMs collectively fine-tune SnRK2 stability, activity, and subcellular dynamics, revealing an intricate feedback system that balances kinase activation and attenuation. By integrating substrate networks with regulatory modifications, this work highlights SnRK2's dual role as both a phosphorylation executor and a PTM-regulated scaffold, offering new perspectives for engineering stress-resilient crops through targeted manipulation of SnRK2 signaling modules.

Identification and characterization of the TmSnRK2 family proteins related to chicoric acid biosynthesis in Taraxacum mongolicum

BACKGROUND

Taraxacum mongolicum is rich in phenolic acids and is widely utilized in food and medicine globally. Our previous research demonstrated that the abscisic acid (ABA) hormone significantly enhances chicoric acid accumulation in T. mongolicum. SNF1-related protein kinase 2s (SnRK2s) are extensively involved in ABA signaling and have the potential to regulate the biosynthesis of phenolic acids.

RESULTS

In this study, liquid chromatography-mass spectrometry (LC-MS) and transcriptomic analyses revealed that the TmbZIP1-Tm4CL1 pathway plays a crucial role in the transcriptional regulation of chicoric acid biosynthesis. Seven TmSnRK2s were identified in T. mongolicum and classified into three groups. Analysis of the TmSnRK2s promoters (2000 bp in length) indicated that the three most prevalent stress-related elements were ABA, methyl jasmonate (MeJA), and light. ABA treatments (0 h, 2 h, 4 h, 8 h, and 24 h) showed that all seven TmSnRK2s were significantly modulated by ABA, with the exception of SnRK2.7. TmSnRK2.2, TmSnRK2.3, TmSnRK2.6, and TmSnRK2.7 were localized in both the cytoplasm and nucleus, whereas TmSnRK2.1 and TmSnRK2.5 were exclusively observed in the cytoplasm. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays indicated that TmSnRK2.1, TmSnRK2.3, TmSnRK2.6, and TmSnRK2.7 interact with TmbZIP1. The motifs 'Q(S/G)(V/D)(D/E)(I/L)××I(I/V)×EA' and 'D×(D/ED××D)' are identified as the core sites that facilitate the binding of TmSnRK2s to TmbZIP1. Dual-luciferase reporter assays demonstrated that TmSnRK2.3 and TmSnRK2.6 enhance the stability of TmbZIP1 binding to proTm4CL1.

CONCLUSION

These findings enhance our understanding of the specific roles of certain members of the TmSnRK2 family in the biosynthesis pathway of chicoric acid.

Multi-Omics Approaches Against Abiotic and Biotic Stress-A Review

Plants face an array of environmental stresses, including both abiotic and biotic stresses. These stresses significantly impact plant lifespan and reduce agricultural crop productivity. Abiotic stresses, such as ultraviolet (UV) radiation, high and low temperatures, salinity, drought, floods, heavy metal toxicity, etc., contribute to widespread crop losses globally. On the other hand, biotic stresses, such as those caused by insects, fungi, and weeds, further exacerbate these challenges. These stressors can hinder plant systems at various levels, including molecular, cellular, and development processes. To overcome these challenges, multi-omics computational approaches offer a significant tool for characterizing the plant's biomolecular pool, which is crucial for maintaining homeostasis and signaling response to environmental changes. Integrating multiple layers of omics data, such as proteomics, metabolomics, ionomics, interactomics, and phenomics, simplifies the study of plant resistance mechanisms. This comprehensive approach enables the development of regulatory networks and pathway maps, identifying potential targets for improving resistance through genetic engineering or breeding strategies. This review highlights the valuable insights from integrating multi-omics approaches to unravel plant stress responses to both biotic and abiotic factors. By decoding gene regulation and transcriptional networks, these techniques reveal critical mechanisms underlying stress tolerance. Furthermore, the role of secondary metabolites in bio-based products in enhancing plant stress mitigation is discussed. Genome editing tools offer promising strategies for improving plant resilience, as evidenced by successful case studies combating various stressors. On the whole, this review extensively discusses an advanced multi-omics approach that aids in understanding the molecular basis of resistance and developing novel strategies to improve crops' or organisms' resilience to abiotic and biotic stresses.

Identification and expression responses of TCP gene family in Opisthopappus taihangensis under abiotic stress

The TCP gene family plays pivotal roles in the development and abiotic stress responses of plants; however, no data has been provided for this gene family in Opisthopappus taihangensis. Based on O. taihangensis genome, 14 TCP genes were identified and divided into two classes (I and II). After tandem and segmental duplication/whole-genome duplication (WGD), more loss and less gain events of OtTCPs occurred, which might be related with the underwent purifying selection during the evolution. The conserved motifs and structures of OtTCP genes contained light response, growth and development, hormone response, and stress-related cis-acting elements. Different OtTCP genes, even duplicated gene pairs, could be expressed in different tissues, which implied that OtTCP genes had diverse function. Among OtTCPs, OtTCP4, 9 and 11 of CYC clade (Class II) presented a relative wide expression pattern with no or one intron. The three TCP genes could be regarded as important candidate factors for O. taihangensis in growth, development and stress response. These results provided some clues and references for the further in-depth exploration of O. taihangensis resistance mechanisms, as well as those of other unique eco-environment plants.

Transcription factors PHR1 and PHR1-like 1 regulate ABA-mediated inhibition of seed germination and stomatal opening in Arabidopsis

Low phosphate (LP) availability significantly impacts crop yield and quality. PHOSPHATE STARVATION RESPONSE1 (PHR1) along with PHR1-like 1 (PHL1) act as a key transcriptional regulator in a plant's adaptive response to LP conditions. Abscisic acid (ABA) plays an important role in how plants respond to environmental stresses like salinity and drought. However, the involvement of PHR1 and PHL1 in ABA response and signalling mechanisms remains to be fully understood. Our findings reveal that PHR1 and PHR1/PHL1 knockout mutations enhance the responsiveness of seed germination, early seedling growth, and stomatal opening to ABA in Arabidopsis. Furthermore, these mutations increase sensitivity to combined LP and ABA stress. In contrast, overexpression of PHR1 or PHL1 reduces this sensitivity in Arabidopsis. Knockout mutations of PHR1 and PHR1/PHL1 also increase sensitivity to salt and osmotic stresses, as well as to combined LP and salinity/osmotic stress, while overexpression of PHR1 or PHL1 reduces their sensitivity in seed germination and early seedling development. Knockout mutations of SPX1 and SPX2, negative regulators of PHR1 and PHL1, decrease sensitivity to ABA and salt/osmotic stresses in Arabidopsis. A group of genes related to ABA metabolism and signalling is significantly affected by the knockout or overexpression of PHR1 and PHL1, with a large proportion of these genes containing PHR1 binding site (P1BS) in their promoters. Moreover, the ABA-sensitive phenotype of phr1 or phr1 phl1 mutants can be rescued by PHR1 homologs from chlorophyte algae, liverwort and rice, suggesting their conserved roles in ABA signalling. These results indicate that PHR1 and its homologs negatively regulate plant responses to ABA in seed germination and stomatal aperture. This study provides new insights into the interplay between Pi homeostasis, abiotic stress and ABA signaling. Moderately increasing the expression of PHR1 or its homologs in crops could be a potential strategy to enhance plant resistance to combined LP and osmotic stress.

Regulatory role of ABA-responsive element binding factors in plant abiotic stress response

As sessile organisms, plants are inevitably threatened by various abiotic stresses. Abiotic stresses seriously affect plant growth and development and crop yield. Plants have evolved complex regulatory networks to resist stresses that occur during their life cycle. The plant hormone abscisic acid (ABA) is accumulated under osmotic stress conditions such as drought, salt, and others. The ABA signaling pathway plays a key role in plant response to abiotic stresses, in which ABA-responsive element binding factors (ABFs) play a crucial role in the whole process. ABFs are a class of basic leucine zipper proteins (bZIPs) that specifically recognize ABA response elements and belong to the a subfamily of the bZIP family. The discoveries of ABFs-mediated tolerance to multiple abiotic stresses, including salinity, drought, cold, and heat stress are highlighted and discussed in this review. The aim of this review is to further analyze the mechanisms of abiotic stress regulation mediated by ABFs and to lay the foundation for breeding superior stress-resistant crop varieties.

Integrated comparative physiological and transcriptomic analyses of Elymus sibiricus L. reveal the similarities and differences in the molecular mechanisms in response to drought and cold stress

Drought and cold crucially affect plant growth and distribution. Plants have evolved complex molecular mechanisms to adapt to such adverse environmental conditions. This study examines two Elymus sibiricus (Es) germplasms differing in resilience to these stresses. Analyzing physiological responses and gene expression changes under drought and cold, it reveals the similarities and differences in their molecular mechanisms that underlie these responses. The results indicate that both drought stress and cold stress severely damage the integrity of the cell membrane in Es. Notably, under cold stress, the accumulation of osmotic regulation substances in Es is more significant, which may be related to the regulation of carbohydrate metabolism (CM)-related genes in cold environments. Furthermore, the response to oxidative stress triggered by cold stress in Es is partially inhibited. The enrichment analysis showed that the DEGs responsive to drought stress in Es were mainly related to the pathway of photosynthesis, whereas the DEGs responsive to cold stress were more associated with the protein processing in endoplasmic reticulum (PPER), highlighting distinct molecular responses. In addition, we discovered that the abscisic acid (ABA) signaling transduction plays a dominant role in mediating the drought resistance mechanism of Es. We have identified 86 key candidate genes related to photosynthesis, Phst, CM, and PPER, including 5 genes that can respond to both drought and cold stress. This study provides a foundation for the molecular mechanisms underlying cold and drought resistance in Es, with insight into its future genetic improvement for stress resistance.

OsbZIP27 coordinates with OsHUB1 and OsHUB2 to modulate drought tolerance in rice

Histone H2B ubiquitination (H2Bub) is positively linked to transcriptional activation, but the genetic programs affected by H2Bub to enhance drought tolerance remain largely unknown. Here, we show that OsbZIP27 interacts directly with OsHUB1/2 to regulate drought tolerance in rice by binding to the promoters of OsHAK1 and OsGLN1 to achieve H2Bub and transcriptional activation. Consistently, mutations in OsbZIP27 reduce transcription of OsHAK1 and OsGLN1, resulting in increased sensitivity to drought stress. Moreover, loss of OsHUB1 and OsHUB2 function causes hypersensitivity to drought stress, whereas OsHUB2 overexpression enhances drought tolerance. Together, our results indicate that OsbZIP27 coordinates with OsHUB1/2 to enhance rice drought tolerance by increasing H2Bub and expression of OsHAK1 and OsGLN1.

Comprehensive Identification of AREB Gene Family in Populus euphratica Oliv. and Functional Analysis of PeAREB04 in Drought Tolerance

The transcription factors in the ABA Response Element Binding (AREB) protein family were differentially regulated under multiple stress conditions; however, functional analyses of AREB in Populus euphratica Oliv. had not been conducted previously. In the present study, the comprehensive identification of the P. euphratica AREB gene family and the function of PeAREB04 in response to drought stress in P. euphratica were elucidated. A comprehensive analysis of the PeAREB family was first performed, followed by the determination of their expression patterns under drought stress. Bioinformatics analysis revealed that thirteen AREB genes were identified across the P. euphratica genome, with these genes distributed across eight chromosomes in a seemingly random pattern. Phylogenetic analysis indicated that the PeAREB genes could be categorized into four distinct branches. Cis-acting element analysis revealed that most PeAREB genes contained multiple hormone- and stress-responsive elements. Transcriptomic sequencing of P. euphratica seedlings under drought stress showed that most PeAREB genes responded rapidly to drought stress in either the leaves or roots. One gene, PeAREB04, was selected for further functional validation due to its significant upregulation in both leaves and roots under drought stress. Overexpression of PeAREB04 in Arabidopsis thaliana resulted in a high survival rate, reduced water loss in isolated leaves, and a significant reduction in stomatal aperture under natural drought conditions. Drought stress simulations using mannitol further demonstrated that overexpression of PeAREB04 significantly enhanced root elongation. These findings indicate that the identification of the PeAREB gene family and the characterization of PeAREB04's role in drought stress have been largely accomplished. Furthermore, the PeAREB04 gene demonstrates considerable potential as a key target for future genetic engineering strategies aimed at enhancing plant drought resistance.

Insight into the transcriptional regulation of key genes involved in proline metabolism in plants under osmotic stress

Proline biosynthesis and catabolism pathways are executed by powerful action of specific enzymes that are subjected to environmental fluctuations at the transcriptional level. Previous researches have demonstrated that osmotic stress-induced upstream events can affect the expression of proline metabolism-related genes, which results in adjustable free proline accumulation to protect plant cells from severe damage. Here, we mainly describe the mechanisms for how some key factors, such as transcription factors, ABA (abscisic acid), Ca2+, MAPK cascades, CK (cytokinin) and phospholipase, in a phosphorylated manner, vividly function in the transcriptional regulation of proline metabolism under osmotic stress. These mechanisms reveal that sustaining of proline homeostasis is an efficient way for plants to adapt to osmotic stress.

Overexpression of the persimmon ABA receptor DkPYL3 gene alters fruit development and ripening in transgenic tomato

Abscisic acid (ABA) is a crucial plant hormone that regulates various aspects of plant development. However, the specific function of the ABA receptor PYL in fruit development has not been fully understood. In this study, we focused on DkPYL3, a member of the ABA receptor subfamily Ⅰ in persimmon, which exhibited high expression levels in fruit, particularly during the young fruit and turning stages. Through yeast two-hybrid (Y2H), firefly luciferase complementation imaging (LCI), protein inhibition assays, and RNA-seq techniques, we identified and characterized the DkPYL3 protein, which was found to inhibit the activity of protein phosphatase type 2 C (PP2C). By heterologous overexpressing (OE) persimmon DkPYL3 in tomatoes, we investigated the impact of the DkPYL3 gene on fruit development and ripening. DkPYL3-OE upregulated the expression of genes related to chlorophyll synthesis and development, leading to a significant increase in chlorophyll content in young fruit. Several fruit quality parameters were also affected by DkPYL3 expression, including sugar content, single fruit weight, and photosynthesis rate. Additionally, fruits overexpressing DkPYL3 exhibited earlier ripening and higher levels of carotenoids and flavonoids compared to wild-type fruits. These results demonstrate the pivotal role of DkPYL3 in ABA-mediated young fruit development, ripening onset, and fruit quality in transgenic tomatoes.

Aquaporin CmPIP2;3 links H2O2 signal and antioxidation to modulate trehalose-induced cold tolerance in melon seedlings

Cold stress severely restricts the growth and development of cold-sensitive crops. Trehalose (Tre), known as the "sugar of life", plays key roles in regulating plant cold tolerance by triggering antioxidation. However, the relevant regulatory mechanism remains unclear. Here, we confirmed that Tre triggers apoplastic hydrogen peroxide (H2O2) production and thus plays key roles in improving the cold tolerance of melon (Cucumis melo var. makuwa Makino) seedlings. Moreover, Tre treatment can promote the transport of apoplastic H2O2 to the cytoplasm. This physiological process may depend on aquaporins. Further studies showed that a Tre-responsive plasma membrane intrinsic protein 2;3 (CmPIP2;3) had strong H2O2 transport function and that silencing CmPIP2;3 significantly weakened apoplastic H2O2 transport and reduced the cold tolerance of melon seedlings. Yeast library and protein-DNA interaction technology were then used to screen 2 Tre-responsive transcription factors, abscisic acid-responsive element (ABRE)-binding factor 2 (CmABF2) and ABRE-binding factor 3 (CmABF3), which can bind to the ABRE motif of the CmPIP2;3 promoter and activate its expression. Silencing of CmABF2 and CmABF3 further dramatically increased the ratio of apoplastic H2O2/cytoplasm H2O2 and reduced the cold tolerance of melon seedlings. This study uncovered that Tre treatment induces CmABF2/3 to positively regulate CmPIP2;3 expression. CmPIP2;3 subsequently enhances the cold tolerance of melon seedlings by promoting the transport of apoplastic H2O2 into the cytoplasm for conducting redox signals and stimulating downstream antioxidation.

Stress-Inducible Expression of HvABF2 Transcription Factor Improves Water Deficit Tolerance in Transgenic Barley Plants

Barley (Hordeum vulgare L.), a major cereal crop grown in arid and semi-arid regions, faces significant yield variability due to drought and heat stresses. In this study, the HvABF2 gene, encoding an ABA-dependent transcription factor, was cloned using specific primers from water deficit-stressed barley seedlings. Gene expression analysis revealed high HvABF2 expression in developing caryopses and inflorescences, with significant induction under stress conditions. The HvABF2 coding sequence was utilized to generate transgenic barley plants with both stress-inducible and constitutive expression, driven by the rice SNAC1 and maize Ubiquitin promoters, respectively. Selected transgenic barley lines, along with control lines, were subjected to water deficit-stress experiments at seedling and flag leaf stages under controlled and greenhouse conditions. The transgenic lines exhibited higher relative water content and stomatal resistance under stress compared to control plants. However, constitutive overexpression of HvABF2 led to growth retardation under well-watered conditions, resulting in reduced plant height, grain weight, and grain number. In contrast, stress-inducible expression mitigated these effects, demonstrating improved drought tolerance without adverse growth impacts. This study highlights that the stress-inducible expression of HvABF2, using the SNAC1 promoter, effectively improves drought tolerance while avoiding the negative pleiotropic effects observed with constitutive expression.

Transcriptional regulation and functional validation analysis of the McbZIP1 in Mentha canadensis L

Monoterpenoids are the main components of Mentha canadensis essential oil. Monoterpene biosynthetic pathways have been explored, but the regulatory mechanisms remain unclarified. We identified an abscisic acid (ABA)-inducible A-type basic leucine zipper (bZIP) transcription factor McbZIP1 that was localized in the nucleus and positively regulates monoterpene synthesis. McbZIP1 was expressed in most M. canadensis tissues and was induced under ABA, mannitol, and NaCl treatments. McbZIP1 had transcriptional activity in yeast and the N terminus (amino acids 75-117) was sufficient for transactivation. Yeast one-hybrid and Dual-Luciferase assays showed that McbZIP1 binds to ABA-responsive elements in the promoter region of limonene synthase gene. Yeast two-hybrid and biomolecular fluorescence complementation assays revealed that McbZIP1 interacts with McSnRK2.4. Overexpression of McbZIP1 in peppermint resulted in dramatically up-regulated monoterpene biosynthesis gene levels and increased menthol contents. The results support a transcriptional regulation mechanism in which McbZIP1 serves as a positive regulator of menthol biogenesis. These findings contribute to the molecular mechanism of monoterpenoid biogenesis, which may have uses in genetic engineering and menthol production.

Protein kinase MeSnRK2.3 positively regulates starch biosynthesis by interacting with the transcription factor MebHLH68 in cassava

Starch biosynthesis involves numerous enzymes and is a crucial metabolic activity in plant storage organs. Sucrose non-fermenting related protein kinase 2 (SnRK2) is an abscisic acid (ABA)-dependent kinase and a significant regulatory enzyme in the ABA signaling pathway. However, whether SnRK2 kinases regulate starch biosynthesis is unclear. In this study, we identified that MeSnRK2.3, encoding an ABA-dependent kinase, was highly expressed in the storage roots of cassava (Manihot esculenta) and was induced by ABA. Overexpression of MeSnRK2.3 in cassava significantly increased the starch content in the storage roots and promoted plant growth. MeSnRK2.3 was further found to interact with the cassava basic helix-loop-helix 68 (MebHLH68) transcription factor in vivo and in vitro. MebHLH68 directly bound to the promoters of sucrose synthase 1 (MeSUS1), granule-bound starch synthase I a (MeGBSSIa), and starch-branching enzyme 2.4 (MeSBE2.4), thereby up-regulating their transcriptional activities. Additionally, MebHLH68 negatively regulated the transcriptional activity of sucrose phosphate synthase B (MeSPSB). Moreover, MebHLH68 phosphorylated by MeSnRK2.3 up-regulated the transcription activity of MeSBE2.4. These findings demonstrated that the MeSnRK2.3-MebHLH68 module connects the ABA signaling pathway and starch biosynthesis in cassava, thereby providing direct evidence of ABA-mediated participation in the sucrose metabolism and starch biosynthesis pathways.

Codonopsis pilosula seedling drought- responsive key genes and pathways revealed by comparative transcriptome

Background

Codonopsis pilosula (Campanulaceae) is a traditional herbal plant that is widely used in China, and the drought stress during the seedling stage directly affects the quality, ultimately impacting its yield. However, the molecular mechanisms underlying the drought resistance of C. pilosula seedlings remain unclear.

Method

Herein, we conducted extensive comparative transcriptome and physiological studies on two distinct C. pilosula cultivar (G1 and W1) seedlings subjected to a 4-day drought treatment.

Results

Our findings revealed that cultivar G1 exhibited enhanced retention of proline and chlorophyll, alongside a marked elevation in peroxidase activity, coupled with diminished levels of malondialdehyde and reduced leaf relative electrolyte leakage compared with cultivar W1. This suggested that cultivar G1 had relatively higher protective enzyme activity and ROS quenching capacity. We discerned a total of 21,535 expressed genes and identified 4,192 differentially expressed genes (DEGs) by RNA sequencing (RNA-seq). Our analysis revealed that 1,764 DEGs unique to G1 underwent thorough annotation and functional categorization utilizing diverse databases. Under drought conditions, the DEGs in G1 were predominantly linked to starch and sucrose metabolic pathways, plant hormone signaling, and glutathione metabolism. Notably, the drought-responsive genes in G1 were heavily implicated in hormonal modulation, such as ABA receptor3-like gene (PYL9), regulation by transcription factors (KAN4, BHLH80, ERF1B), and orchestration of drought-responsive gene expression. These results suggest that cultivar G1 possesses stronger stress tolerance and can better adapt to drought growing conditions. The congruence between qRT-PCR validation and RNA-seq data for 15 DEGs further substantiated our findings.

Conclusion

Our research provides novel insights into the physiological adaptations of C. pilosula to arid conditions and lays the groundwork for the development of new, drought-tolerant C. pilosula cultivars.

Integrated Analysis of Transcriptome and Metabolome Provides Insights into Flavonoid Biosynthesis of Blueberry Leaves in Response to Drought Stress

Blueberries (Vaccinium spp.) are extremely sensitive to drought stress. Flavonoids are crucial secondary metabolites that possess the ability to withstand drought stress. Therefore, improving the drought resistance of blueberries by increasing the flavonoid content is crucial for the development of the blueberry industry. To explore the underlying molecular mechanism of blueberry in adaptation to drought stress, we performed an integrated analysis of the metabolome and transcriptome of blueberry leaves under drought stress. We found that the most enriched drought-responsive genes are mainly involved in flavonoid biosynthesis and plant hormone signal transduction pathways based on transcriptome data and the main drought-responsive metabolites come from the flavonoid class based on metabolome data. The UDP-glucose flavonoid 3-O-glucosyl transferase (UFGT), flavonol synthase (FLS), and anthocyanidin reductase (ANR-2) genes may be the key genes for the accumulation of anthocyanins, flavonols, and flavans in response to drought stress in blueberry leaves, respectively. Delphinidin 3-glucoside and delphinidin-3-O-glucoside chloride may be the most important drought-responsive flavonoid metabolites. VcMYB1, VcMYBPA1, MYBPA1.2, and MYBPA2.1 might be responsible for drought-induced flavonoid biosynthesis and VcMYB14, MYB14, MYB102, and MYB108 may be responsible for blueberry leaf drought tolerance. ABA responsive elements binding factor (ABF) genes, MYB genes, bHLH genes, and flavonoid biosynthetic genes might form a regulatory network to regulate drought-induced accumulation of flavonoid metabolites in blueberry leaves. Our study provides a useful reference for breeding drought-resistant blueberry varieties.

Unveiling the secrets of abiotic stress tolerance in plants through molecular and hormonal insights

Phytohormones are signaling substances that control essential elements of growth, development, and reactions to environmental stress. Drought, salt, heat, cold, and floods are a few examples of abiotic factors that have a significant impact on plant development and survival. Complex sensing, signaling, and stress response systems are needed for adaptation and tolerance to such pressures. Abscisic acid (ABA) is a key phytohormone that regulates stress responses. It interacts with the jasmonic acid (JA) and salicylic acid (SA) signaling pathways to direct resources toward reducing the impacts of abiotic stressors rather than fighting against pathogens. Under exposure to nanoparticles, the plant growth hormones also function as molecules that regulate stress and are known to be involved in a variety of signaling cascades. Reactive oxygen species (ROS) are detected in excess while under stress, and nanoparticles can control their formation. Understanding the way these many signaling pathways interact in plants will tremendously help breeders create food crops that can survive in deteriorating environmental circumstances brought on by climate change and that can sustain or even improve crop production. Recent studies have demonstrated that phytohormones, such as the traditional auxins, cytokinins, ethylene, and gibberellins, as well as more recent members like brassinosteroids, jasmonates, and strigolactones, may prove to be significant metabolic engineering targets for creating crop plants that are resistant to abiotic stress. In this review, we address recent developments in current understanding regarding the way various plant hormones regulate plant responses to abiotic stress and highlight instances of hormonal communication between plants during abiotic stress signaling. We also discuss new insights into plant gene and growth regulation mechanisms during stress, phytohormone engineering, nanotechnological crosstalk of phytohormones, and Plant Growth-Promoting Rhizobacteria's Regulatory Powers (PGPR) via the involvement of phytohormones.

Genome‑wide analysis of the GT8 gene family in apple and functional identification of MhGolS2 in saline-alkali tolerance

Members of the glycosyltransferase 8 (GT8) family play an important role in regulating gene expression in response to many kinds of biotic and abiotic stress. In this study, 56 members of the apple GT8 family were identified, and their gene structure, phylogenetic relationships, chromosomal localization, and promoter cis-acting elements were comprehensively analyzed. Subsequently, 20 genes were randomly selected from the evolutionary tree for qRT-PCR detection, and it was found that MhGolS2 was significantly overexpressed under stress conditions. MhGolS2 was isolated from M.halliana and transgenic Arabidopsis thaliana, tobacco and apple callus tissues were successfully obtained. The transgenic plants grew better under stress conditions with higher polysaccharide, chlorophyll and proline content, lower conductivity and MDA content, significant increase in antioxidant enzyme activities (SOD, POD, CAT) and maintenance of low Na+/K+ as compared to the wild type. Meanwhile, the expression levels of reactive oxygen species-related genes (AtSOD, AtPOD, and AtCAT), Na+ transporter genes (AtCAX5, AtSOS1, and AtHKT1), H+-ATPase genes (AtAHA2 and AtAHA8), and raffinose synthesis-related genes (AtSTS, AtRFS1, and AtMIPS) were significantly up-regulated, while the expression levels of K+ transporter genes (AtSKOR, AtHAK5) were reduced. Finally, the Y2H experiment confirmed the interaction between MhGolS2 and MhbZIP23, MhMYB1R1, MhbHLH60, and MhNAC1 proteins. The above results indicate that MhGolS2 can improve plant saline-alkali tolerance by promoting polysaccharide synthesis, scavenging reactive oxygen species, and increasing the activity of antioxidant enzymes. This provides excellent stress resistance genes for the stress response regulatory network in apple.

Metabolic profiles in drought-tolerant wheat with enhanced abscisic acid sensitivity

Global warming has led to the expansion of arid lands and more frequent droughts, which are the largest cause of global food production losses. In our previous study, we developed TaPYLox wheat overexpressing the plant hormone abscisic acid (ABA) receptor, which is important for the drought stress response in plants. TaPYLox showed resistance to drought stress and acquired water-saving traits that enable efficient grain production with less water use. In this study, we used TaPYLox to identify ABA-dependent and -independent metabolites in response to drought stress. We compared the variation of metabolites in wheat under well-watered, ABA treatment, and drought stress conditions using the ABA-sensitive TaPYLox line and control lines. The results showed that tagatose and L-serine were ABA-dependently regulated metabolites, because their stress-induced accumulation was increased by ABA treatment in TaPYLox. In contrast, L-valine, L-leucine, and DL-isoleucine, which are classified as branched chain amino acids, were not increased by ABA treatment in TaPYLox, suggesting that they are metabolites regulated in an ABA-independent manner. Interestingly, the accumulation of L-valine, L-leucine, and DL-isoleucine was suppressed in drought-tolerant TaPYLox under drought stress, suggesting that drought-tolerant wheat might be low in these amino acids. 3-dehydroshikimic acid and α-ketoglutaric acid were decreased by drought stress in an ABA-independent manner. In this study, we have succeeded in identifying metabolites that are regulated by drought stress in an ABA-dependent and -independent manner. The findings of this study should be useful for future breeding of drought-tolerant wheat.

Metabolomic and transcriptomic analyses highlight metabolic regulatory networks of Salvia miltiorrhiza in response to replant disease

BACKGROUND

Salvia miltiorrhiza, a well-known traditional Chinese medicine, frequently suffers from replant diseases that adversely affect its quality and yield. To elucidate S. miltiorrhiza's metabolic adaptations to replant disease, we analyzed its metabolome and transcriptome, comparing normal and replant diseased plants for the first time.

RESULTS

We identified 1,269 metabolites, 257 of which were differentially accumulated metabolites, and identified 217 differentially expressed genes. Integrated transcriptomic and metabolomic analyses revealed a significant up-regulation and co-expression of metabolites and genes associated with plant hormone signal transduction and flavonoid biosynthesis pathways in replant diseases. Within plant hormone signal transduction pathway, plants afflicted with replant disease markedly accumulated indole-3-acetic acid and abscisic acid, correlating with high expression of their biosynthesis-related genes (SmAmidase, SmALDH, SmNCED, and SmAAOX3). Simultaneously, changes in hormone concentrations activated plant hormone signal transduction pathways. Moreover, under replant disease, metabolites in the local flavonoid metabolite biosynthetic pathway were significantly accumulated, consistent with the up-regulated gene (SmHTC1 and SmHTC2). The qRT-PCR analysis largely aligned with the transcriptomic results, confirming the trends in gene expression. Moreover, we identified 10 transcription factors co-expressed with differentially accumulated metabolites.

CONCLUSIONS

Overall, we revealed the key genes and metabolites of S. miltiorrhiza under replant disease, establishing a robust foundation for future inquiries into the molecular responses to combat replant stress.

Transcriptome Analysis of the Regulatory Mechanisms of Holly (Ilex dabieshanensis) under Salt Stress Conditions

The holly Ilex dabieshanensis K. Yao & M. B. Deng, a tree endemic to the Dabieshan Mountains region in China, is a commonly used landscaping plant. Like other crops, its growth is affected by salt stress. The molecular mechanism underlying salt tolerance in holly is still unclear. In this study, we used NaCl treatment and RNA sequencing (RNA-seq) at different times to identify the salt stress response genes of holly. A total of 4775 differentially expressed genes (DEGs) were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the DEGs obtained at different salt treatment times (3, 6, 9, 12, and 24 h), as compared to control (ck, 0 h), showed that plant hormone signal transduction and carotenoid biosynthesis were highly enriched. The mechanism by which holly responds to salt stress involves many plant hormones, among which the accumulation of abscisic acid (ABA) and its signal transduction may play an important role. In addition, ion homeostasis, osmotic metabolism, accumulation of antioxidant enzymes and nonenzymatic antioxidant compounds, and transcription factors jointly regulate the physiological balance in holly, providing important guarantees for its growth and development under conditions of salt stress. These results lay the foundation for studying the molecular mechanisms of salt tolerance in holly and for the selection of salt-tolerant varieties.

Physiological Characteristics and Transcriptomic Responses of Pinus yunnanensis Lateral Branching to Different Shading Environments

Pinus yunnanensis is an important component of China's economic development and forest ecosystems. The growth of P. yunnanensis seedlings experienced a slow growth phase, which led to a long seedling cultivation period. However, asexual reproduction can ensure the stable inheritance of the superior traits of the mother tree and also shorten the breeding cycle. The quantity and quality of branching significantly impact the cutting reproduction of P. yunnanensis, and a shaded environment affects lateral branching growth, development, and photosynthesis. Nonetheless, the physiological characteristics and the level of the transcriptome that underlie the growth of lateral branches of P. yunnanensis under shade conditions are still unclear. In our experiment, we subjected annual P. yunnanensis seedlings to varying shade intensities (0%, 25%, 50%, 75%) and studied the effects of shading on growth, physiological and biochemical changes, and gene expression in branching. Results from this study show that shading reduces biomass production by inhibiting the branching ability of P. yunnanensis seedlings. Due to the regulatory and protective roles of osmotically active substances against environmental stress, the contents of soluble sugars, soluble proteins, photosynthetic pigments, and enzyme activities exhibit varying responses to different shading treatments. Under shading treatment, the contents of phytohormones were altered. Additionally, genes associated with phytohormone signaling and photosynthetic pathways exhibited differential expression. This study established a theoretical foundation for shading regulation of P. yunnanensis lateral branch growth and provides scientific evidence for the management of cutting orchards.

Integrated proteomic, transcriptomic, and metabolomic profiling reveals that the gibberellin-abscisic acid hub runs flower development in the Chinese orchid Cymbidium sinense

The seasonal flowering Chinese Cymbidium produce an axillary floral meristem and require a dormancy period during cold conditions for flower development. However, the bud activation mechanism remains elusive. This study evaluates the multi-omics across six stages of flower development, along with functional analysis of core genes to decipher the innate mechanism of floral bud initiation and outgrowth in the Chinese orchid Cymbidium sinense. Transcriptome and proteome analyses identified 10 modules with essential roles in floral bud dormancy and activation. Gene clusters in the early stages of flower development were mainly related to flowering time regulation and meristem determination, while the late stages were correlated with hormone signaling pathways. The metabolome identified 69 potential hormones in which gibberellin (GA) and abscisic acid (ABA) were the main regulatory hubs, and GA4 and GA53 exhibited a reciprocal loop. Extraneous GA application caused rapid elongation of flower buds and promoted the expression of flower development genes. Contrarily, exogenous ABA application extended the dormancy process and ABA inhibitors induced dormancy release. Moreover, CsAPETALA1 (CsAP1) was identified as the potential target of ABA for floral bud activation. Transformation of CsAP1 in Arabidopsis and its transient overexpression in C. sinense protoplasts not only affected flowering time and floral organ morphogenesis in Arabidopsis but also orchestrated the expression of flowering and hormone regulatory genes. The presence of ABA response elements in the CsAP1 promoter, rapid downregulation of CsAP1 after exogenous ABA application, and the activation of the floral bud after ABA inhibitor treatment suggest that ABA can control bud outgrowth through CsAP1.

Integration of nitrate and abscisic acid signaling in plants

To meet the demands of the new Green Revolution and sustainable agriculture, it is important to develop crop varieties with improved yield, nitrogen use efficiency, and stress resistance. Nitrate is the major form of inorganic nitrogen available for plant growth in many well-aerated agricultural soils, and acts as a signaling molecule regulating plant development, growth, and stress responses. Abscisic acid (ABA), an important phytohormone, plays vital roles in integrating extrinsic and intrinsic responses and mediating plant growth and development in response to biotic and abiotic stresses. Therefore, elucidating the interplay between nitrate and ABA can contribute to crop breeding and sustainable agriculture. Here, we review studies that have investigated the interplay between nitrate and ABA in root growth modulation, nitrate and ABA transport processes, seed germination regulation, and drought responses. We also focus on nitrate and ABA interplay in several reported omics analyses with some important nodes in the crosstalk between nitrate and ABA. Through these insights, we proposed some research perspectives that could help to develop crop varieties adapted to a changing environment and to improve crop yield with high nitrogen use efficiency and strong stress resistance.

Genome-Wide Identification and Expression Profiling of the ABF Transcription Factor Family in Wheat (Triticum aestivum L.)

Members of the abscisic acid (ABA)-responsive element (ABRE) binding factor (ABF) and ABA-responsive element binding protein (AREB) families play essential roles in the regulation of ABA signaling pathway activity and shape the ability of plants to adapt to a range of stressful environmental conditions. To date, however, systematic genome-wide analyses focused on the ABF/AREB gene family in wheat are lacking. Here, we identified 35 ABF/AREB genes in the wheat genome, designated TaABF1-TaABF35 according to their chromosomal distribution. These genes were further classified, based on their phylogenetic relationships, into three groups (A-C), with the TaABF genes in a given group exhibiting similar motifs and similar numbers of introns/exons. Cis-element analyses of the promoter regions upstream of these TaABFs revealed large numbers of ABREs, with the other predominant elements that were identified differing across these three groups. Patterns of TaABF gene expansion were primarily characterized by allopolyploidization and fragment duplication, with purifying selection having played a significant role in the evolution of this gene family. Further expression profiling indicated that the majority of the TaABF genes from groups A and B were highly expressed in various tissues and upregulated following abiotic stress exposure such as drought, low temperature, low nitrogen, etc., while some of the TaABF genes in group C were specifically expressed in grain tissues. Regulatory network analyses revealed that four of the group A TaABFs (TaABF2, TaABF7, TaABF13, and TaABF19) were centrally located in protein-protein interaction networks, with 13 of these TaABF genes being regulated by 11 known miRNAs, which play important roles in abiotic stress resistance such as drought and salt stress. The two primary upstream transcription factor types found to regulate TaABF gene expression were BBR/BPC and ERF, which have previously been reported to be important in the context of plant abiotic stress responses. Together, these results offer insight into the role that the ABF/AREB genes play in the responses of wheat to abiotic stressors, providing a robust foundation for future functional studies of these genes.

Genome-wide identification and expression analysis of the HAK/KUP/KT gene family in Moso bamboo

The K+ uptake permease/high-affinity K+/K+ transporter (KUP/HAK/KT) family is the most prominent group of potassium (K+) transporters, playing a key role in K+ uptake, transport, plant growth and development, and stress tolerance. However, the presence and functions of the KUP/HAK/KT family in Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau), the fastest-growing plant, have not been studied. In this study, we identified 41 KUP/HAK/KT genes (PeHAKs) distributed across 18 chromosomal scaffolds of the Moso bamboo genome. PeHAK is a typical membrane protein with a conserved structural domain and motifs. Phylogenetic tree analysis classified PeHAKs into four distinct clusters, while collinearity analysis revealed gene duplications resulting from purifying selection, including both tandem and segmental duplications. Enrichment analysis of promoter cis-acting elements suggested their plausible role in abiotic stress response and hormone induction. Transcriptomic data and STEM analyses indicated that PeHAKs were involved in tissue and organ development, rapid growth, and responded to different abiotic stress conditions. Subcellular localization analysis demonstrated that PeHAKs are predominantly expressed at the cell membrane. In-situ PCR experiments confirmed that PeHAK was mainly expressed in the lateral root primordia. Furthermore, the involvement of PeHAKs in potassium ion transport was confirmed by studying the potassium ion transport properties of a yeast mutant. Additionally, through homology modeling, we revealed the structural properties of HAK as a transmembrane protein associated with potassium ion transport. This research provides a solid basis for understanding the classification, characterization, and functional analysis of the PeHAK family in Moso bamboo.

OsNAC120 balances plant growth and drought tolerance by integrating GA and ABA signaling in rice

The crosstalk between gibberellin (GA) and abscisic acid (ABA) signaling is crucial for balancing plant growth and adaption to environmental stress. Nevertheless, the molecular mechanism of their mutual antagonism still remains to be fully clarified. In this study, we found that knockout of the rice NAC (NAM, ATAF1/2, CUC2) transcription factor gene OsNAC120 inhibits plant growth but enhances drought tolerance, whereas OsNAC120 overexpression produces the opposite results. Exogenous GA can rescue the semi-dwarf phenotype of osnac120 mutants, and further study showed that OsNAC120 promotes GA biosynthesis by transcriptionally activating the GA biosynthetic genes OsGA20ox1 and OsGA20ox3. The DELLA protein SLENDER RICE1 (SLR1) interacts with OsNAC120 and impedes its transactivation ability, and GA treatment can remove the inhibition of transactivation activity caused by SLR1. On the other hand, OsNAC120 negatively regulates rice drought tolerance by repressing ABA-induced stomatal closure. Mechanistic investigation revealed that OsNAC120 inhibits ABA biosynthesis via transcriptional repression of the ABA biosynthetic genes OsNCED3 and OsNCED4. Rice OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9 (OsSAPK9) physically interacts with OsNAC120 and mediates its phosphorylation, which results in OsNAC120 degradation. ABA treatment accelerates OsNAC120 degradation and reduces its transactivation activity. Together, our findings provide evidence that OsNAC120 plays critical roles in balancing GA-mediated growth and ABA-induced drought tolerance in rice. This research will help us to understand the mechanisms underlying the trade-off between plant growth and stress tolerance and to engineer stress-resistant, high-yielding crops.

Structural and functional characterization of genes PYL-PP2C-SnRK2s in the ABA signalling pathway of Cucurbita pepo

BACKGROUND

The core regulation of the abscisic acid (ABA) signalling pathway comprises the multigenic families PYL, PP2C, and SnRK2. In this work, we conducted a genome-wide study of the components of these families in Cucurbita pepo.

RESULTS

The bioinformatic analysis of the C. pepo genome resulted in the identification of 19 CpPYL, 102 CpPP2C and 10 CpSnRK2 genes. The investigation of gene structure and protein motifs allowed to define 4 PYL, 13 PP2C and 3 SnRK2 subfamilies. RNA-seq analysis was used to determine the expression of these gene families in different plant organs, as well as to detect their differential gene expression during germination, and in response to ABA and cold stress in leaves. The specific tissue expression of some gene members indicated the relevant role of some ABA signalling genes in plant development. Moreover, their differential expression under ABA treatment or cold stress revealed those ABA signalling genes that responded to ABA, and those that were up- or down-regulated in response to cold stress. A reduced number of genes responded to both treatments. Specific PYL-PP2C-SnRK2 genes that had potential roles in germination were also detected, including those regulated early during the imbibition phase, those regulated later during the embryo extension and radicle emergence phase, and those induced or repressed during the whole germination process.

CONCLUSIONS

The outcomes of this research open new research lines for agriculture and for assessing gene function in future studies.

Identification and Characterization of the AREB/ABF Gene Family in Three Orchid Species and Functional Analysis of DcaABI5 in Arabidopsis

AREB/ABF (ABA response element binding) proteins in plants are essential for stress responses, while our understanding of AREB/ABFs from orchid species, important traditional medicinal and ornamental plants, is limited. Here, twelve AREB/ABF genes were identified within three orchids' complete genomes and classified into three groups through phylogenetic analysis, which was further supported with a combined analysis of their conserved motifs and gene structures. The cis-element analysis revealed that hormone response elements as well as light and stress response elements were widely rich in the AREB/ABFs. A prediction analysis of the orchid ABRE/ABF-mediated regulatory network was further constructed through cis-regulatory element (CRE) analysis of their promoter regions. And it revealed that several dominant transcriptional factor (TF) gene families were abundant as potential regulators of these orchid AREB/ABFs. Expression profile analysis using public transcriptomic data suggested that most AREB/ABF genes have distinct tissue-specific expression patterns in orchid plants. Additionally, DcaABI5 as a homolog of ABA INSENSITIVE 5 (ABI5) from Arabidopsis was selected for further analysis. The results showed that transgenic Arabidopsis overexpressing DcaABI5 could rescue the ABA-insensitive phenotype in the mutant abi5. Collectively, these findings will provide valuable information on AREB/ABF genes in orchids.

Genome-wide identification and expression profiling of the ABI5 gene family in foxtail millet (Setaria italica)

BACKGROUND

ABA Insensitive 5 (ABI5) is a basic leucine zipper transcription factor that crucially influences plant growth, development, and stress response. However, there is minimal research on the ABI5 family in foxtail millet.

RESULTS

In this study, 16 ABI5 genes were identified in foxtail millet, and their sequence composition, gene structures, cis-acting elements, chromosome positions, and gene replication events were analyzed. To more thoroughly evaluate the developmental mechanisms of the SiABI5 family during evolution, we selected three dicotyledons (S. lycopersicum, A. thaliana, F. tataricum) and three (Z. mays, O. sativa, S. bicolor) specific representative monocotyledons associated with foxtail millet for comparative homology mapping. The results showed that foxtail millet ABI5 genes had the best homology with maize. A promoter sequence analysis showed that the SiABI5s contain numerous cis-acting elements related to hormone and stress responses, indicating that the regulation of SiABI5 expression was complex. The expression responses of 16 genes in different tissues, seed germination, and ear development were analyzed. A total of six representative genes were targeted from five subfamilies to characterize their gene expression responses to four different abiotic stresses. Overexpression of SiABI5.12 confers tolerance to osmotic stress in transgenic Arabidopsis thaliana, which demonstrated the function of SiABI5 responded to abiotic stress.

CONCLUSIONS

In summary, our research results comprehensively characterized the SiABI5 family and can provide a valuable reference for demonstrating the role of SiABI5s in regulating abiotic stress responses in foxtail millet.

A B-box transcription factor OsBBX17 regulates saline-alkaline tolerance through the MAPK cascade pathway in rice

Rice OsBBX17 encodes a B-box zinc finger transcription factor in which the N-terminal B-box structural domain interacts with OsMPK1. In addition, it directly binds to the G-box of OsHAK2 and OsHAK7 promoters and represses their transcription. Under saline-alkaline conditions, the expression of OsBBX17 was inhibited. Meanwhile, activation of the OsMPK1-mediated mitogen-activated protein kinase cascade pathway caused OsMPK1 to interact with OsBBX17 and phosphorylate OsBBX17 at the Thr-95 site. It reduced OsBBX17 DNA-binding activity and enhanced saline-alkaline tolerance by deregulating transcriptional repression of OsHAK2 and OsHAK7. Genetic assays showed that the osbbx17-KO had an excellent saline-alkaline tolerance, whereas the opposite was in OsBBX17-OE. In addition, overexpression of OsMPK1 significantly improved saline-alkaline tolerance, but knockout of OsMPK1 caused an increased sensitivity. Further overexpression of OsBBX17 in the osmpk1-KO caused extreme saline-alkaline sensitivity, even a quick death. OsBBX17 was validated in saline-alkaline tolerance from two independent aspects, transcriptional level and post-translational protein modification, unveiling a mechanistic framework by which OsMPK1-mediated phosphorylation of OsBBX17 regulates the transcription of OsHAK2 and OsHAK7 to enhance the Na+ /K+ homeostasis, which partially explains light on the molecular mechanisms of rice responds to saline-alkaline stress via B-box transcription factors for the genetic engineering of saline-alkaline tolerant crops.

Positive regulation of ABA signaling by MdCPK4 interacting with and phosphorylating MdPYL2/12 in Arabidopsis

The phytohormone abscisic acid (ABA) regulates plant growth and development and stress resistance through the ABA receptor PYLs. To date, no interaction between CPK and PYL has been reported, even in Arabidopsis and rice. In this study, we found that MdCPK4 from Malus domestica (Md for short) interacts with two MdPYLs, MdPYL2/12, in the nucleus and the cytoplasm in vivo and phosphorylates the latter in vitro as well. Compared with the wild type (WT), the MdCPK4- or MdPYL2/12-overexpressing Arabidopsis lines showed more sensitivity to ABA, and therefore stronger drought resistance. The ABA-related genes (ABF1, ABF2, ABF4, RD29A and SnRK2.2) were significantly upregulated in the overexpressing (OE) lines after ABA treatment. These results indicate that MdCPK4 and MdPYL2/12 act as positive regulators in response to ABA-mediated drought resistance in apple. Our results reveal the relationship between MdCPK4 and MdPYL2/12 in ABA signaling, which will further enrich the molecular mechanism of drought resistance in plants.

Functional characterization of GhNAC2 promoter conferring hormone- and stress-induced expression: a potential tool to improve growth and stress tolerance in cotton

The GhNAC2 transcription factor identified from G. herbaceum improves root growth and drought tolerance through transcriptional reprogramming of phytohormone signaling. The promoter of such a versatile gene could serve as an important genetic engineering tool for biotechnological application. In this study, we identified and characterized the promoter of GhNAC2 to understand its regulatory mechanism. GhNAC2 transcription factor increased in root tissues in response to GA, ethylene, auxin, ABA, mannitol, and NaCl. In silico analysis revealed an overrepresentation of cis-regulatory elements associated with hormone signaling, stress responses and root-, pollen-, and seed-specific promoter activity. To validate their role in GhNAC2 function/regulation, an 870-bp upstream regulatory sequence was fused with the GUS reporter gene (uidA) and expressed in Arabidopsis and cotton hairy roots for in planta characterization. Histochemical GUS staining indicated localized expression in root tips, root elongation zone, root primordia, and reproductive tissues under optimal growth conditions. Mannitol, NaCl, auxin, GA, and ABA, induced the promoter-driven GUS expression in all tissues while ethylene suppressed the promoter activity. The results show that the 870 nt fragment of the GhNAC2 promoter drives root-preferential expression and responds to phytohormonal and stress signals. In corroboration with promoter regulation, GA and ethylene pathways differentially regulated root growth in GhNAC2-expressing Arabidopsis. The findings suggest that differential promoter activity governs the expression of GhNAC2 in root growth and stress-related functions independently through specific promoter elements. This multifarious promoter can be utilized to develop yield and climate resilience in cotton by expanding the options to control gene regulation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01411-2.

Genome-wide identification of PYL/PYR-PP2C (A)-SnRK2 genes in Eutrema and their co-expression analysis in response to ABA and abiotic stresses

ABA signaling core components PYR/PYL, group A PP2C and SnRK2 play important roles in various environmental stress responses of plants. This study identified 14 PYR/PYL, 9 PP2C (A), and 10 SnRK2 genes from halophytic Eutrema. Phylogenetic analysis showed 4 EsPYR/PYL, 4 EsPP2C (A) and 3 EsSnRK2 subfamilies characterized, which was supported by their gene structures and protein motifs. Large-scale segmental duplication event was demonstrated to be a major contributor to expansion of the EsPYL-PP2C (A)-SnRK2 gene families. Synteny relationship analysis revealed more orthologous PYL-PP2C (A)-SnRK2 gene pairs located in collinear blocks between Eutrema and Brassica than that between Eutrema and Arabidopsis. RNA-seq and qRT-PCR revealed EsABI1, EsABI2 and EsHAL2 showed a significantly up-regulated expression in leaves and roots in response to ABA, NaCl or cold stress. Three markedly co-expression modules of ABA/R-brown, NaCl/L-lightsteelblue1 and Cold/R-lightgreen were uncovered to contain EsPYL-PP2C (A)-SnRK2 genes by WGCNA analysis. GO and KEGG analysis indicated that the genes of ABA/R-brown module containing EsHAB1, EsHAI2 and EsSnRK2.6 were enriched in proteasome pathway. Further, EsHAI2-OE transgenic Arabidopsis lines showed significantly enhanced seeds germination and seedlings growth. This work provides a new insight for elucidating potential molecular functions of PYL-PP2C (A)-SnRK2 responding to ABA and abiotic stresses.

The role of strigolactone analog (GR24) in endogenous hormone metabolism and hormone-related gene expression in tobacco axillary buds

KEY MESSAGE

Strigolactone has the potential to influence hormone metabolism, in addition to having a role in inhibiting axillary bud elongation, which could be regulated by the expression of phytohormones-related genes. The elongation of axillary buds affects the economic benefits of tobacco. In this study, it was investigated the effect of strigolactone (SL) on the elongation of tobacco axillary buds and its endogenous hormone metabolism and related gene expression by applying the artificial analog of SL, GR24, and an inhibitor of SL synthesis, TIS-108, to the axillary buds. The results showed that the elongation of axillary buds was significantly inhibited by GR24 on day 2 and day 9. Ultra-high-performance liquid-chromatography-mass spectrometry results further showed that SL significantly affected the metabolism of endogenous plant hormones, altering both their levels and the ratios between each endogenous hormone. Particularly, the levels of auxin (IAA), trans-zeatin-riboside (tZR), N6-(∆2-isopentenyl) adenine (iP), gibberellin A4 (GA4), jasmonic acid (JA), and jasmonoyl isoleucine (JA-Ile) were decreased after GR24 treatment on day 9, but the levels of 1-aminocyclopropane-1-carboxylic acid (ACC) and gibberellin A1 (GA1) were significantly increased. Further analysis of endogenous hormonal balance revealed that after the treatment with GR24 on day 9, the ratio of IAA to cytokinin (CTK) was markedly increased, but the ratios of IAA to abscisic acid (ABA), salicylic acid (SA), ACC, JAs, and, GAs were notably decreased. In addition, according to RNA-seq analysis, multiple differentially expressed genes were found, such as GH3.1, AUX/IAA, SUAR20, IPT, CKX1, GA2ox1, ACO3, ERF1, PR1, and HCT, which may play critical roles in the biosynthesis, deactivation, signaling pathway of phytohormones, and the biosynthesis of flavonoids to regulate the elongation of axillary buds in tobacco. This work lays the certain theoretical foundation for the application of SL in regulating the elongation of axillary buds of tobacco.

Nuclear factor OsNF-YC5 modulates rice seed germination by regulating synergistic hormone signaling

Regulation of seed dormancy/germination is of great importance for seedling establishment and crop production. Nuclear factor-Y (NF-Y) transcription factors regulate plant growth and development, as well as stress responses; however, their roles in seed germination remain largely unknown. In this study, we reported that NF-Y gene OsNF-YC5 knockout increased, while its overexpression reduced, the seed germination in rice (Oryza sativa L.). ABA-induced seed germination inhibition assays showed that the osnf-yc5 mutant was less sensitive but OsNF-YC5-overexpressing lines were more sensitive to exogenous ABA than the wild type. Meanwhile, MeJA treatment substantially enhanced the ABA sensitivity of OsNF-YC5-overexpressing lines during seed germination. Mechanistic investigations revealed that the interaction of OSMOTIC STRESS/ABA-ACTIVATED PROTEIN KINASE 9 (SAPK9) with OsNF-YC5 enhanced the stability of OsNF-YC5 by protein phosphorylation, while the interaction between JASMONATE ZIM-domain protein 9 (OsJAZ9) and OsNF-YC5 repressed OsNF-YC5 transcriptional activity and promoted its degradation. Furthermore, OsNF-YC5 transcriptionally activated ABA catabolic gene OsABA8ox3, reducing ABA levels in germinating seeds. However, the transcriptional regulation of OsABA8ox3 by OsNF-YC5 was repressed by addition of OsJAZ9. Notably, OsNF-YC5 improved seed germination under salinity conditions. Further investigation showed that OsNF-YC5 activated the high-affinity K+ transporter gene (OsHAK21) expression, and addition of SAPK9 could increase the transcriptional regulation of OsHAK21 by OsNF-YC5, thus substantially reducing the ROS levels to enhance seed germination under salt stress. Our findings establish that OsNF-YC5 integrates ABA and JA signaling during rice seed germination, shedding light on the molecular networks of ABA-JA synergistic interaction.

Phytohormone Response of Drought-Acclimated Illicium difengpi (Schisandraceae)

Illicium difengpi (Schisandraceae), which is an endemic, medicinal, and endangered species found in small and isolated populations that inhabit karst mountain areas, has evolved strategies to adapt to arid environments and is thus an excellent material for exploring the mechanisms of tolerance to severe drought. In experiment I, I. difengpi plants were subjected to three soil watering treatments (CK, well-watered treatment at 50% of the dry soil weight for 18 days; DS, drought stress treatment at 10% of the dry soil weight for 18 days; DS-R, drought-rehydration treatment at 10% of the dry soil weight for 15 days followed by rewatering to 50% of the dry soil weight for another 3 days). The effects of the drought and rehydration treatments on leaf succulence, phytohormones, and phytohormonal signal transduction in I. difengpi plants were investigated. In experiment II, exogenous abscisic acid (ABA, 60 mg L-1) and zeatin riboside (ZR, 60 mg L-1) were sprayed onto DS-treated plants to verify the roles of exogenous phytohormones in alleviating drought injury. Leaf succulence showed marked changes in response to the DS and DS-R treatments. The relative concentrations of ABA, methyl jasmonate (MeJA), salicylic acid glucoside (SAG), and cis-zeatin riboside (cZR) were highly correlated with relative leaf succulence. The leaf succulence of drought-treated I. difengpi plants recovered to that observed with the CK treatment after exogenous application of ABA or ZR. Differentially expressed genes involved in biosynthesis and signal transduction of phytohormones (ABA and JA) in response to drought stress were identified by transcriptomic profiling. The current study suggested that the phytohormones ABA, JA, and ZR may play important roles in the response to severe drought and provides a preliminary understanding of the physiological mechanisms involved in phytohormonal regulation in I. difengpi, an endemic, medicinal, and highly drought-tolerant plant found in extremely small populations in the karst region of South China.

Roles of abscisic acid and auxin in plants during drought: A molecular point of view

Plant responses to drought are mediated by hormones like ABA (abscisic acid) and auxin. These hormones regulate plant drought responses by modulating various physiological and biological processes via cell signaling. ABA accumulation and signaling are central to plant drought responses. Auxin also regulates plant adaptive responses to drought, especially via signal transduction mediated by the interaction between ABA and auxin. In this review, we explored the interactive roles of ABA and auxin in the modulation of stomatal movement, root traits and accumulation of reactive oxygen species associated with drought tolerance.

Update on stomata development and action under abiotic stress

Stomata, key gatekeepers of plant hydration, have long been known to play a pivotal role in mitigating the impacts of abiotic stressors. However, the complex molecular mechanisms underscoring this role remain unresolved fully and continue to be the subject of research. In the context of water-use efficiency (WUE), a key indicator of a plant's ability to conserve water, this aspect links intrinsically with stomatal behavior. Given the pivotal role of stomata in modulating water loss, it can be argued that the complex mechanisms governing stomatal development and function will significantly influence a plant's WUE under different abiotic stress conditions. Addressing these calls for a concerted effort to strengthen plant adaptability through advanced, targeted research. In this vein, recent studies have illuminated how specific stressors trigger alterations in gene expression, orchestrating changes in stomatal pattern, structure, and opening. This reveals a complex interplay between stress stimuli and regulatory sequences of essential genes implicated in stomatal development, such as MUTE, SPCH, and FAMA. This review synthesizes current discoveries on the molecular foundations of stomatal development and behavior in various stress conditions and their implications for WUE. It highlights the imperative for continued exploration, as understanding and leveraging these mechanisms guarantee enhanced plant resilience amid an ever-changing climatic landscape.

Metabolic pathways engineering for drought or/and heat tolerance in cereals

Drought (D) and heat (H) are the two major abiotic stresses hindering cereal crop growth and productivity, either singly or in combination (D/+H), by imposing various negative impacts on plant physiological and biochemical processes. Consequently, this decreases overall cereal crop production and impacts global food availability and human nutrition. To achieve global food and nutrition security vis-a-vis global climate change, deployment of new strategies for enhancing crop D/+H stress tolerance and higher nutritive value in cereals is imperative. This depends on first gaining a mechanistic understanding of the mechanisms underlying D/+H stress response. Meanwhile, functional genomics has revealed several stress-related genes that have been successfully used in target-gene approach to generate stress-tolerant cultivars and sustain crop productivity over the past decades. However, the fast-changing climate, coupled with the complexity and multigenic nature of D/+H tolerance suggest that single-gene/trait targeting may not suffice in improving such traits. Hence, in this review-cum-perspective, we advance that targeted multiple-gene or metabolic pathway manipulation could represent the most effective approach for improving D/+H stress tolerance. First, we highlight the impact of D/+H stress on cereal crops, and the elaborate plant physiological and molecular responses. We then discuss how key primary metabolism- and secondary metabolism-related metabolic pathways, including carbon metabolism, starch metabolism, phenylpropanoid biosynthesis, γ-aminobutyric acid (GABA) biosynthesis, and phytohormone biosynthesis and signaling can be modified using modern molecular biotechnology approaches such as CRISPR-Cas9 system and synthetic biology (Synbio) to enhance D/+H tolerance in cereal crops. Understandably, several bottlenecks hinder metabolic pathway modification, including those related to feedback regulation, gene functional annotation, complex crosstalk between pathways, and metabolomics data and spatiotemporal gene expressions analyses. Nonetheless, recent advances in molecular biotechnology, genome-editing, single-cell metabolomics, and data annotation and analysis approaches, when integrated, offer unprecedented opportunities for pathway engineering for enhancing crop D/+H stress tolerance and improved yield. Especially, Synbio-based strategies will accelerate the development of climate resilient and nutrient-dense cereals, critical for achieving global food security and combating malnutrition.

SUPPRESSOR OF MAX2 LIKE 6, 7, and 8 Interact with DDB1 BINDING WD REPEAT DOMAIN HYPERSENSITIVE TO ABA DEFICIENT 1 to Regulate the Drought Tolerance and Target SUCROSE NONFERMENTING 1 RELATED PROTEIN KINASE 2.3 to Abscisic Acid Response in Arabidopsis

SUPPRESSOR OF MAX2-LIKE 6, 7, and 8 (SMXL6,7,8) function as repressors and transcription factors of the strigolactone (SL) signaling pathway, playing an important role in the development and stress tolerance in Arabidopsis thaliana. However, the molecular mechanism by which SMXL6,7,8 negatively regulate drought tolerance and ABA response remains largely unexplored. In the present study, the interacting protein and downstream target genes of SMXL6,7,8 were investigated. Our results showed that the substrate receptor for the CUL4-based E3 ligase DDB1-BINDING WD-REPEAT DOMAIN (DWD) HYPERSENSITIVE TO ABA DEFICIENT 1 (ABA1) (DWA1) physically interacted with SMXL6,7,8. The degradation of SMXL6,7,8 proteins were partially dependent on DWA1. Disruption of SMXL6,7,8 resulted in increased drought tolerance and could restore the drought-sensitive phenotype of the dwa1 mutant. In addition, SMXL6,7,8 could directly bind to the promoter of SUCROSE NONFERMENTING 1 (SNF1)-RELATED PROTEIN KINASE 2.3 (SnRK2.3) to repress its transcription. The mutations in SnRK2.2/2.3 significantly suppressed the hypersensitivity of smxl6/7/8 to ABA-mediated inhibition of seed germination. Conclusively, SMXL6,7,8 interact with DWA1 to negatively regulate drought tolerance and target ABA-response genes. These data provide insights into drought tolerance and ABA response in Arabidopsis via the SMXL6,7,8-mediated SL signaling pathway.

Aspartyl tRNA-synthetase (AspRS) gene family enhances drought tolerance in poplar through BABA-PtrIBIs-PtrVOZ signaling module

BACKGROUND

Drought stress is a prevalent abiotic stress that significantly hinders the growth and development of plants. According to studies, β-aminobutyric acid (BABA) can influence the ABA pathway through the AtIBI1 receptor gene to enhance cold resistance in Arabidopsis. However, the Aspartate tRNA-synthetase (AspRS) gene family, which acts as the receptor for BABA, has not yet been investigated in poplar. Particularly, it is uncertain how the AspRS gene family (PtrIBIs)r can resist drought stress after administering various concentrations of BABA to poplar.

RESULTS

In this study, we have identified 12 AspRS family genes and noted that poplar acquired four PtrIBI pairs through whole genome duplication (WGD). We conducted cis-action element analysis and found a significant number of stress-related action elements on different PtrIBI genes promoters. The expression of most PtrIBI genes was up-regulated under beetle and mechanical damage stresses, indicating their potential role in responding to leaf damage stress. Our results suggest that a 50 mM BABA treatment can alleviate the damage caused by drought stress in plants. Additionally, via transcriptome sequencing, we observed that the partial up-regulation of BABA receptor genes, PtrIBI2/4/6/8/11, in poplars after drought treatment. We hypothesize that poplar responds to drought stress through the BABA-PtrIBIs-PtrVOZ coordinated ABA signaling pathway. Our research provides molecular evidence for understanding how plants respond to drought stress through external application of BABA.

CONCLUSIONS

In summary, our study conducted genome-wide analysis of the AspRS family of P. trichocarpa and identified 12 PtrIBI genes. We utilized genomics and bioinformatics to determine various characteristics of PtrIBIs such as chromosomal localization, evolutionary tree, gene structure, gene doubling, promoter cis-elements, and expression profiles. Our study found that certain PtrIBI genes are regulated by drought, beetle, and mechanical damage implying their crucial role in enhancing poplar stress tolerance. Additionally, we observed that external application of low concentrations of BABA increased plant drought resistance under drought stress. Through the BABA-PtrIBIs-PtrVOZ signaling module, poplar plants were able to transduce ABA signaling and regulate their response to drought stress. These results suggest that the PtrIBI genes in poplar have the potential to improve drought tolerance in plants through the topical application of low concentrations of BABA.