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Analyzing salinity tolerance in grass carp (Ctenopharyngodon idella): Insights from genome-wide association study and genomic selection.

Grass carp (Ctenopharyngodon idella) is one of the most widely cultured freshwater fish species globally. However, the expansion of its farming scale faces severe limitation owing to freshwater scarcity; therefore, the development of strains with greater salinity tolerance is key for expanding production using brackish water resources. To investigate the genetic basis of salinity tolerance in grass carp, a genome-wide association study (GWAS) was conducted using 200 individuals representing extreme phenotypes, namely salinity-tolerant and salinity-sensitive groups. In total, 17 single nucleotide polymorphisms (SNPs) related to salinity tolerance were detected, which were distributed across 11 chromosomes. Through gene annotation, 38 candidate genes were obtained from these loci. Enrichment analysis revealed these candidate genes are primarily implicated in key biological processes, including osmotic regulation, energy metabolism, and stress responses. Analyses of different SNP densities revealed that the 5 K SNP density panel can balance prediction accuracy and computational efficiency. The BayesA model achieved the highest prediction accuracy under the GWAS_Evenly selection strategy, with substantial reductions in mean absolute error and mean square error. This study reveals the genetic mechanisms of salinity tolerance in grass carp, which might be optimized through genomic selection, and provides insights for selectively breeding new varieties with greater salinity tolerance.

Animals

Amino Acid Substitutions in the Na+/K+-ATPase May Contribute to Salinity Tolerance in Insects.

Environmental salinity levels vary naturally across terrestrial ecosystems but can be heightened locally by coastal proximity and desertification as well as human activities such as road salt application and agriculture. Since salt is essential for many physiological processes in insects, rising environmental sodium concentrations may drive behavioral changes, where insects select environments and food sources with suitable sodium levels, or evolutionary changes in constitutive or plastic physiological mechanisms to process salt, potentially altering ecological dynamics and species interactions.Numerous hematophagous (blood feeding) insects such as the yellow-fever mosquito Aedes aeqypti are known to be able to breed in relatively saline environments. Among phytophagous (plant feeding) insects, grasshoppers can be important herbivores in arid and coastal salt-affected regions, whereas the monarch butterfly (Danaus plexippus) appears to perform relatively well on milkweed host plants growing in roadsides influenced by salt runoff. Several of these insects share a common trait: amino acid substitutions in the first extracellular loop of the Na+/K+-ATPase (NKA), a sodium pump crucial for maintaining ion balance. For the monarch these substitutions confer resistance to toxic cardenolides from milkweeds, but it is unclear whether NKA substitutions may influence salt tolerance.Here, we investigate whether the NKA substitutions found in these insects may contribute to salt tolerance using gene-edited Drosophila melanogaster mutant strains as models. We show that flies with substitution Q111L (found in Aedes mosquitoes) or a combination of Q111L and A119S (found in grasshoppers) exhibited greater salt tolerance, whereas flies carrying the combination of substitutions found in the monarch (Q111V, A119S, and N122H) did not.Our results suggest that the monarch may rely on alternate mechanisms for salt tolerance and that its NKA substitutions are important primarily for cardenolide resistance. However, substitution Q111L and the combination of Q111L and A119S may be relevant for salt tolerance in a variety of insects. Uncovering mechanisms of salt tolerance enhances our understanding of species distributions, ecological interactions, and evolutionary physiology in response to changing environmental salinity levels.

Journal Article

Genome-wide characterization of ZmCRY genes: unveiling stress response mechanisms and the role of ZmCRYPHR2 in salinity tolerance.

BACKGROUND: Blue light serves as a crucial environmental signal regulating plant growth and development. The cryptochrome (CRY) family represents a key class of blue light receptors involved in these processes, as well as plant growth, development, and defense. However, the functions of CRYs in maize remain largely unexplored. RESULTS: In this study, nine ZmCRY genes were identified and found to be unevenly distributed across five chromosomes. Gene structure and conserved motif analyses revealed that ZmCRYs within the same phylogenetic groups are highly conserved. Synteny analysis indicated a close evolutionary relationship between ZmCRYs and their homologs in Oryza sativa. Promoter analysis identified diverse cis-regulatory elements linked to light response, stress tolerance, and hormone signaling. RT-qPCR analysis showed that ZmCRYs respond to various abiotic and biotic stresses, including high salinity, drought, nitrogen deficiency, Fusarium verticillioides, and Puccinia polysora. Functional studies demonstrated that ZmCRYPHR2, localized in chloroplasts and the cytoplasmic membrane, plays a role in scavenging reactive oxygen and regulating maize salt tolerance. Haplotype 2 of ZmCRYPHR2 was identified as the preferred haplotype in a panel of 269 inbred lines. CONCLUSIONS: These findings provide a comprehensive genomic and functional characterization of the ZmCRY gene family, with ZmCRYPHR2 identified as a pivotal regulator of salt tolerance, offering valuable genetic insights for the development of stress-resilient maize breeding.

Zea mays

Untargeted metabolomics reveals anion and organ-specific metabolic responses of salinity tolerance in willow.

Willows can alleviate soil salinisation while generating sustainable feedstock for biorefinery, yet the metabolomic adaptations underlying their tolerance remain poorly understood. Salix miyabeana was treated with two environmentally abundant salts, NaCl and Na2SO4, in a 12-week pot trial. Willows tolerated salts across all treatments (up to 9.1 dS m-1 soil ECe), maintaining biomass while selectively partitioning ions, confining Na+ to roots and accumulating Cl- andin the canopy and adapting to osmotic stress via reduced stomatal conductance. Untargeted metabolomics captured >5000 putative compounds, including 278 core willow metabolome compounds constitutively produced across organs. Across all treatments, salinity drove widespread metabolic reprogramming, altering 28% of the overall metabolome, with organ-tailored strategies. Comparing salt forms at equimolar sodium, shared differentially abundant metabolites were limited to 3% of the metabolome, representing the generalised salinity response, predominantly in roots. Anion-specific metabolomic responses were extensive. NaCl reduced carbohydrates and tricarboxylic acid cycle intermediates, suggesting potential carbon and energy resource pressure, and accumulated root structuring compounds, antioxidant flavonoids, and fatty acids. Na2SO4 salinity triggered accumulation of sulphur-containing larger peptides, suggesting excess sulphate incorporation leverages ion toxicity to produce specialised salt-tolerance-associated metabolites. This high-depth picture of the willow metabolome underscores the importance of capturing plant adaptations to salt stress at organ scale and considering ion-specific contributions to soil salinity.

Salix

Development of molecular markers associated with saline-alkali tolerance in rapeseed (Brassica napus L.).

A total of 947 saline-alkaline tolerance-related molecular markers and a 5K cGPS genotyping chipwere developed, providing practical tools for marker-assisted selection and molecular design breeding of saline-alkaline-tolerant rapeseed. Rapeseed (Brassica napus L.) has relatively strong tolerance to saline-alkaline stress and shows great potential for the sustainable utilization and improvement of saline-alkaline soils. However, the breeding of highly tolerant cultivars still mainly depends on conventional hybridization combined with phenotype-based selection, which constrains breeding efficiency. In this study, previously reported saline-alkaline tolerance-related genes from rapeseed, rice, maize, wheat, sorghum, and Arabidopsis were collected. Candidate gene-based association analysis enabled the development of molecular markers and a genotyping chip. A total of 483 significantly associated genes were identified, among which 355 genes contained favorable haplotypes. Molecular markers were successfully developed for 275 genes, including 746 KASP and 201 InDel marker pairs, and four marker pairs were randomly selected for validation. In addition, a 5K cGPS liquid-phase chip (HZSW-cGPS-BRNAP-04), was developed and showed a high call rate and excellent reproducibility in genotyping. These markers and the chip are expected to improve the breeding efficiency of saline-alkaline-tolerant rapeseed cultivars. Overall, this study provides useful tools for early-generation evaluation and marker-assisted selection (MAS), and provides a foundation for molecular design breeding of saline-alkali-tolerant rapeseed.

Brassica napus

CaCl2 Priming Boosts Salinity-Alkalinity Tolerance in Germinating Soybean by Reducing DNA Oxidative Damage and Enhancing Ca2+ -ROS Signaling Crosstalk.

Soybean (Glycine max) seed germination is highly sensitive to saline-alkaline stress. Seed priming represents an effective strategy to mitigate its detrimental effects. However, the optimal priming conditions (agent, concentration, duration) and the underlying molecular mechanisms remain poorly understood. This study investigated the effects of priming with distilled water (Control), calcium chloride (CaCl2), melatonin (MT), and proline (Pro) under saline-alkaline stress on soybean seed germination and the molecular basis of enhanced tolerance. Evaluation of ten germination-related parameters revealed that priming with 100 mM CaCl2 for 12 h significantly enhanced the germination rate. Physiological analyses demonstrated that CaCl2 priming effectively reduced reactive oxygen species (ROS) accumulation by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while decreasing malondialdehyde (MDA) content. Furthermore, CaCl2 priming activated the Ca2+ signaling pathway by increasing radicle Ca2+ content and upregulating the expression levels of Ca2+ signaling-related genes (e.g., GmCAM7, GmCNGC2, GmCNGC19, GmMPK2, and GmMKK2). Additionally, CaCl2 priming significantly enhanced DNA damage repair capacity of soybean cultivars with differing saline-alkaline tolerance. This was manifested by reduced DNA oxidative damage and decreased random amplified polymorphic DNA (RAPD) polymorphism, thereby enhancing genomic stability and alleviating cell cycle arrest. These findings deepen our understanding of the complex regulatory role of calcium signaling in plant abiotic stress responses and provide important novel theoretical insights for improving crop resilience.

Glycine max

The genetic basis of chloride exclusion in grapevines.

Mediterranean regions are among the most important areas for global grape production, characterized by dry climates and frequent challenges associated with soil salinity. In these environments, chloride toxicity is a major factor limiting vine growth and fruit quality. Despite the critical role of chloride exclusion in salinity tolerance, the genetic mechanisms underlying this trait remain poorly understood. In this study, we analyzed natural variation in chloride exclusion using a diverse panel of 335 accessions representing 18 wild and cultivated Vitis species. This panel, comprising accessions from the southwestern United States and Mexico, captures a broad range of evolutionary adaptations to abiotic stress and provides a valuable genetic resource for breeding efforts aimed at introducing novel traits. Using genome-wide association and quantitative trait loci (QTL) mapping, we identified a major QTL on chromosome 8, now designated qClEx8.1, containing candidate genes encoding cation/H⁺ exchangers (CHXs), which are involved in ion transport and homeostasis. To validate these findings, we analyzed a mapping population derived from Vitis acerifolia longii 9018 and the commercial rootstock GRN3, confirming the chromosome 8 locus as a major determinant of chloride exclusion. Structural variant analysis revealed nonsynonymous substitutions within CHX genes that may influence protein function and salinity tolerance. Additionally, we discovered a novel QTL on chromosome 19 enriched with G-type lectin S-receptor-like serine/threonine-protein kinases, known regulators of stress signaling. By integrating phenotypic and genomic data across a diverse Vitis collection, this study advances our understanding of the genetic architecture underlying chloride exclusion and highlights candidate genes for breeding salt-tolerant rootstocks.

Vitis

Comparative analysis of genomic variations among different Cdo1 paralogs for salinity-adaptation in oysters.

Under rapid climate change and anthropogenic activities, oysters, a global aquaculture species, are subjected to exacerbated culturing environments, especially for those living in in-shore estuarine species, such as Suminoe oysters Crassostrea ariakensis. This study aims to investigate the molecular mechanisms of salinity adaptation of C. ariakensis. We performed an expression genome-wide association study (eGWAS) to compare genetic regulation among 5 paralogous copies of a key salinity-related gene, cysteine dioxygenase 1 (Cdo1). A total of 40 significant eSNPs with 82 adjacent eGenes were identified in 2 copies (Cdo1_26639 and Cdo1_1666). We identified only trans-eSNPs for Cdo1_26639 and more cis-eSNPs for Cdo1_1666, and different eGenes for these 2 Cdo1 copies, which indicated that the expressional regulation of these paralogs may undergo distinct pathways. We identified 3 eGenes that exhibited identical expression patterns with Cdo1_26639 and Cdo1_1666, including 6-Pgdh, Trapp and tandem copy of Cdo1_27337. The expression correlation between Cdo1 copies and eGenes was enhanced under salinity stresses, suggesting the crucial role of eGenes in regulating Cdo1's expression in response to salinity changes. Our results provide comprehensive identification and comparison of eSNPs across different paralogous copies of one gene, along with insights into the molecular mechanisms underlying salinity tolerance, and genetic markers for breeding salinity-resistant oysters.

Animals

Genome-wide identification of the Glutathione Peroxidase (GPX) gene family in Taxodium distichum and functional characterization of TdGPX9 in enhancing salt tolerance.

This study systematically identified 10 TdGPX genes in Taxodium distichum, demonstrating that the nucleocytoplasmic-localized TdGPX9 plays a pivotal role in salt stress response. Overexpression of TdGPX9 significantly enhances salt tolerance by strengthening the antioxidant defense system and improving root system plasticity under stress. Taxodium distichum is a premier coniferous species renowned for its exceptional waterlogging and salinity tolerance, serving as a vital forest resource for coastal afforestation and wetland ecological restoration. Within the physiological framework of plant stress resistance, the glutathione peroxidase (GPX) family represents a cornerstone of the antioxidant enzymatic system, playing a critical role in scavenging reactive oxygen species and maintaining cellular redox homeostasis. In this study, 10 TdGPX genes were identified via a comprehensive genome-wide analysis and mapped across eight chromosomes. These genes possess a highly conserved Thioredoxin_like domain, with structural and motif analyses revealing a well-maintained arrangement of conserved motifs within each subgroup. The promoter analysis identified a sophisticated regulatory network enriched with cis-acting elements responsive to light, phytohormones, and abiotic stresses, suggesting their integration into diverse signaling pathways. Expression profiling across various tissues and embryonic developmental stages further highlighted the versatile roles of TdGPX members in plant growth and organogenesis. Notably, qRT-PCR analysis identified the nucleocytoplasmic-localized TdGPX9 as a primary respondent to salinity. Functional validation demonstrated that TdGPX9 overexpression significantly enhances salt tolerance in transgenic Arabidopsis and T. distichum callus by strengthening the antioxidant defense system. Furthermore, TdGPX9 promoted root system plasticity under stress, as evidenced by increased lateral root density. These findings provide a systematic basis for understanding the redox-regulatory mechanisms in baldcypress and offer vital genetic resources for improving forest resilience in coastal wetland ecosystems.

Salt Tolerance

Tandem gene duplication facilitates intertidal adaptation in atypical mangrove plants.

Mangrove plants, originating from inland ancestors, have independently adapted to extreme intertidal zones characterized by salt and hypoxia stress. While typical mangroves exhibit specialized phenotypes, like viviparous seeds and salt secretion, atypical clades that have thrived without such traits are particularly suitable for exploring the molecular and physiological basis underlying plant adaptation to intertidal zones. We assembled a chromosome-level genome of an atypical mangrove, Scyphiphora hydrophylacea, the only mangrove species in Gentianales. Similar to other mangroves, S. hydrophylacea colonized intertidal zones during climatic optimum periods of sea-level rise. Despite lacking recent whole-genome duplications (WGDs), its genome acquired extensive tandem gene duplications (TDs), leading to the rapid expansion of key salt- and hypoxia-related genes. Transcriptome data further corroborated that TD-driven gene expansions contribute to stress tolerance. Specifically, the expansion of genes involved in cation transmembrane transport, osmotic regulation, and oxidative stress response may enhance salinity tolerance, and the expansion of signal transduction and energy metabolism genes in hypoxia-response pathways may confer waterlogging tolerance. Therefore, in the absence of large-scale gene duplication, the rapid expansion of core genes involved in salt and hypoxia tolerance through tandem duplication may represent a key force driving the adaptation of atypical mangroves. These findings also provide valuable insights for crop improvement strategies aimed at enhancing environmental resilience while maintaining phenotypic stability.

Gene Duplication

A deep metagenomic atlas of Qinghai-Xizang Plateau lakes reveals their microbial diversity and salinity adaptation mechanisms.

The Qinghai-Xizang Plateau (QXP), harboring the planet's highest density of plateau lakes, offers an exceptional biogeographic environment for studying extremophilic microbial communities and their adaptation to salinity. Through deep metagenomic sequencing, we construct the Qinghai-Xizang Lake Sediment Genome (QXLSG) catalog, a high-resolution genomic catalog comprising 5,866 metagenome-assembled genomes (MAGs), 58.16 million non-redundant protein encoding genes, and 19,008 biosynthetic gene clusters. Notably, 80.78% of the 2,742 species-level MAGs represent undescribed taxa, significantly expanding the known microbial diversity. Salinity emerges as the primary environmental factor influencing microbial community. Functional annotation highlights that the "salt-out" strategy, particularly the uptake of glycine betaine, is the main mechanism for salinity tolerance. This strategy is prevalent in both hypersaline lake communities and the dominant microbial phyla. Overall, this study provides a crucial genetic resource for future bioprospecting and deepens our understanding of the fundamental mechanisms of microbial adaptation to extreme saline environments.

Lakes

Potential survival strategies of novel comammox and nitrite-oxidizing Nitrospira synthesizing osmoprotectants in a wastewater microbiome treating high-ammonia brackish landfill leachate.

BACKGROUND: In the late stages of landfill operation, leachate becomes brackish and contains high concentrations of ammonia with limited organic carbon. At leachate treatment facilities, it is typically subjected to nitrification followed by denitrification, with methanol supplied as an external electron donor. This unique environment may harbor novel microorganisms, including nitrifiers. Although a variety of microorganisms are involved in nitrification, their substrate specificity and salinity tolerance remain insufficiently understood. In this study, a genome-centric metagenome analysis was conducted on the microbiome from a leachate treatment facility at a closed landfill. RESULTS: A total of 68 metagenome-assembled genomes (MAGs) were reconstructed, including 64 putative novel species. Among these, two Nitrospira MAGs were recovered: a novel complete ammonia-oxidizing bacterium (comammox), Nitrospira LAS72 (88.72% completeness, 2.10% contamination), and canonical nitrite-oxidizing Nitrospira LAS18 (99.98% completeness, 2.29% contamination). Comparative genomic analysis with 260 publicly available Nitrospira genomes revealed that LAS18 represents a new sub-lineage within lineage VII of the Nitrospira genus. Two ammonia-oxidizing archaea (AOA), Candidatus Nitrosocosmicus LAS21 and Nitrosarchaeum LAS73, were also identified, while canonical ammonia-oxidizing bacteria were not detected. Given the brackish conditions (1.23% salinity) and the methanol-fed operation of the treatment facility, the genomic potential for osmotic stress adaptation and methanol metabolism was investigated. Comammox Nitrospira LAS72 harbors biosynthetic pathways for several compatible solutes (osmoprotectants), including glycine betaine, proline, trehalose, and L-glutamate. Moreover, comammox Nitrospira LAS72 possesses genetic potential for oxidizing formaldehyde, suggesting that it may exploit these methanol-derived intermediates as energy sources. These features indicate that LAS72 may withstand osmotic fluctuations through the production of various osmoprotectants and thrive under the unique conditions of a methanol-fed environment. CONCLUSIONS: The discovery of novel comammox Nitrospira and canonical Nitrospira forming a new sub-lineage within lineage VII of the Nitrospira genus in an ammonia-rich brackish environment provides the first genomic evidence for evolutionary adaptation among nitrifiers to saline, methanol-fed environments. These findings enhance our understanding of the ecological and evolutionary dynamics shaping nitrifier communities in complex treatment ecosystems. Video Abstract.

Ammonia

Comparative phylogenomics and transcriptional regulatory networks of AQPs, HSPs, and LEA proteins in salt-stressed Portulaca oleracea.

Soil salinization severely threatens global food security, necessitating systematic investigations of halophytes like Portulaca oleracea to decode the molecular mechanisms of environmental resilience. Utilizing an integrated framework of deep learning-based genome annotation (58,817 predicted genes; 96.5% BUSCO completeness), multi-tissue RNA-Seq, phylogenomics, and gene regulatory network (GRN) inference, the synergistic orchestration of 78 aquaporins (AQPs), 525 heat shock proteins (HSPs), and 119 late embryogenesis abundant (LEA) proteins was elucidated. The active transcriptome, encompassing 39,065 expressed loci, revealed a systemic growth-defense trade-off. Tissues displayed distinct adaptive mechanisms: leaves modulated intracellular water balance via specialized AQPs, whereas adult roots maintained proteostasis through robust HSP20/HSP70 induction. Phylogenomic clustering across 154 species demonstrated that salinity tolerance constitutes an evolutionary mosaic, identifying 81 halophyte-exclusive orthogroups and 1129 species-specific clusters. Comparative topology across six independent GRNs (4.2M-5.3 M edges) unmasked a highly modular transcriptional reprogramming strategy governed by a core apparatus of 22 stress-exclusive regulators, with functional enrichment heavily prioritizing protein dimerization and chromatin remodeling. Theoretically, the distinct convergence of Trihelix transcription factors with guard cell differentiation pathways offers a candidate transcriptomic framework to explain the plant's characteristic C4-CAM photosynthetic plasticity under severe osmotic pressure. Practically, these evolutionary blueprints and specific master switches transcend single-gene transgenic limitations. Utilizing these root-sustained and stress-inducible targets under localized promoters provides a naturally optimized, network-level precision engineering roadmap to transfer robust, compartmentalized halotolerance to sensitive glycophytic crops.

Gene Regulatory Networks

Chromosome-level Genome Assembly of the Halophytic Turfgrass Zoysia macrostachya.

Zoysia macrostachya Franch. & Sav. is a halophytic perennial turfgrass in the Poaceae family, commonly found in the coastal regions of Korea, Japan, and East Asia. Z. macrostachya thrives in high-salinity environments, making it an excellent model for studying abiotic stress resilience. In this study, we present a chromosome-level genome assembly of Z. macrostachya, constructed using Oxford Nanopore long reads, Illumina short reads, and Omni-C sequencing data. The assembly spans 329.78 Mb across 20 chromosomes, with a scaffold N50 of 19.24 Mb, and includes complete telomeric sequences at both ends. The assembly showed 97.8% complete BUSCOs, indicating high genome completeness. Repeat element and gene annotation identified 44.03% of the genome as repetitive elements and 33,474 protein-coding genes. The gene annotation showed 97.1% complete BUSCOs and 86.92% functionally characterized genes. Macrosynteny analysis highlighted highly collinear relationships with related species, providing a foundational understanding of the Z. macrostachya genomic structure. This high-quality genome serves as a valuable resource for advancing salinity tolerance research and improving the genetic diversity of Zoysia species.

Genome, Plant

Adaptive Evolution for Freshwater Adaptation in Coilia nasus by Directional Selection on Osmoregulation Genes.

The molecular mechanisms underlying the adaptation to freshwater habitats in fish of marine origin remain unclear. Grenadier anchovies, such as Coilia nasus, originate from marine environments and include both anadromous and freshwater-resident conspecifics, making them ideal for studying adaptive evolution from marine to freshwater habitats. We conducted a comparative population genomic and transcriptome analysis of two distinct C. nasus lineages, one anadromous and the other freshwater-resident, collected from mainstream and estuarine regions of the Yangtze River, China. By genome-wide genotyping of the anadromous and the freshwater-resident populations, we observed significant divergence in osmoregulation, energy metabolism, and immune response pathways associated with ecological adaptation and energy expenditure for migration. Some ion transport genes such as CAMK1, ATP1α3, KCNJ1 and SLC30A2 were identified that may contribute to freshwater adaptation. Notably, numerous mineralocorticoid signalling genes (e.g., NR3C2, SGK1, ATP1α3, KCNJ1) exhibit dynamic change between the anadromous and freshwater populations, suggesting an important role for the hormone cortisol in regulating salinity acclimation in euryhaline fish. Among these genes, the ion channel ATP1α3 experienced adaptive amino acid substitutions (Val317Ile and Thr329Ser), which appear to be evolutionary hotspots across migratory species based on ortholog comparisons. These variants may facilitate sodium/potassium transport and highlight salinity tolerance as a key driver of divergence in anadromous fish transitioning to freshwater. These results enhance our understanding of the genetic basis underlying freshwater adaptation for an anadromous fish across osmotic boundaries.

Animals

Functional study of the AfRAP2 gene in Amorpha fruticosa L. tolerance to saline-alkali and drought stress.

BACKGROUND: Amorpha fruticosa L. is a leguminous shrub with high tolerance to drought, poor soil, and saline-alkali stress conditions. As a member of the family of transcription factors in higher plants, the ethylene response factor AP2/ERF plays a crucial role in both plant adaptation to abiotic stress and in growth and development. In this study, based on genes identified from the transcriptomic sequencing of Amorpha fruticosa L. under drought stress, the upregulated gene AfRAP2 was isolated from its seedlings, with the aim of elucidating its stress-response function using molecular biological techniques. RESULTS: In this study, the AfRAP2 gene was cloned from the leaves of Amorpha fruticosa L. using RT-PCR. Bioinformatics analysis revealed that AfRAP2 contains an AP2 domain and belongs to the DREB subfamily of the AP2/ERF transcription factor family, showing close phylogenetic relationships with LaEREBP from Lathyrus albus. Real-time quantitative PCR (RT-qPCR) results indicate that AfRAP2 is expressed in various tissues of Amorpha fruticosa L., with the highest expression in leaves and the lowest in stems, furthermore, its expression is significantly upregulated in roots and leaves upon induction by NaHCO3 and PEG6000. Subcellular localization experiments confirmed that the AfRAP2 protein is localized to the nucleus, and GUS histochemical staining assay revealed that its promoter drives GUS expression in anthers. Resistance analysis of overexpressing yeast strains showed that yeast transformed with the AfRAP2 gene exhibited significantly better growth under sorbitol, mannitol, and NaHCO3 stress conditions compared to the control, indicating that this gene enhances yeast tolerance to drought and saline-alkali stress. We screened transgenic tobacco and Populus davidiana × P. alba var. Pyramidalis. The results showed that under natural drought and saline-alkali stress treatments, the transgenic lines exhibited significantly improved growth and higher activities of the physiological indicators of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) compared with wild-type plants, indicating that the overexpression of the AfRAP2 gene plays a key role in the response to saline-alkali stress and drought stress. CONCLUSION: In summary, AfRAP2 contains an AP2 domain and belongs to the DREB subfamily of transcription factors, under abiotic stress induced by NaHCO₃ and mannitol, it can induce the expression of the AfRAP2 gene in tobacco and Populus davidiana×P. alba var. pyramidalis. AfRAP2 plays a vital role in the plant response to saline-alkali stress and drought stress and is a promising candidate gene for stress-tolerant breeding.

Plant Proteins