Global warming has resulted in frequent droughts worldwide, significantly affecting plant normal growth and development. Polyphenol oxidase (PPO), a copper-containing redox enzyme in plants, serves multiple functions. However, limited research has investigated the role of PPO in regulating plant drought adaptation. In this study, PmPPO was isolated from Prunus mira Koehne, the wild ancestor of cultivated peaches, which is a rare tree species known for its high stress tolerance under extreme conditions. Our results indicated that PmPPO was preferentially expressed in young roots, with its expression significantly induced by drought and abscisic acid (ABA). Overexpression of PmPPO in plants demonstrated enhanced tolerance to drought stress. Under drought stress, transgenic plants exhibited increased antioxidant enzyme activity, improved reactive oxygen species (ROS) scavenging capacity, and reduced cellular damage compared to wild-type (WT). Moreover, PmPPO overexpression facilitated anthocyanin accumulation by regulating the expression of genes involved in anthocyanin biosynthesis following drought treatment. Additionally, yeast two-hybrid (Y2H) and Luciferase complementation imaging (LCI) assays confirmed interactions between PmPPO and both PmRad23d and PmRGLG2. These findings introduce new molecular targets for genetic manipulation in peach germplasm improvement and present potential candidate genes for screening stress tolerance through molecular breeding.

With the intensification of global climate change, environmental issues such as soil salinization and drought have exerted an increasingly prominent impact on plants. Tibetan peach (Amygdalus mira), a rare native tree species of the genus Amygdalus in the Rosaceae family, possesses extremely strong tolerance to cold, drought, and disease stress. In the previous study, we found that the protein abundance of a calcium-binding protein, AmCML24, was significantly upregulated in Tibetan peach under drought stress, leading us to hypothesize that it plays an important role in the molecular mechanisms underlying plant responses to abiotic stresses. Therefore, this study focuses on AmCML24, aiming to preliminarily characterize the stress-tolerant function of AmCML24 and explore its biological role in plant tolerance to saline-alkali and drought stresses. Results demonstrated that AmCML24 responds to multiple abiotic stresses. Yeast and Arabidopsis thaliana lines overexpressing AmCML24 exhibited enhanced tolerance to NaCl, NaHCO3, and mannitol stresses, with a significant upregulation in the expression of stress-responsive genes. This study lays a solid foundation for deciphering the stress regulatory network of Tibetan peach and elucidating the biological function of AmCML24, while also providing a scientific basis for the genetic improvement, exploitation, and utilization of Tibetan peach germplasm resources.

Low temperature has a serious effect on Actinidia arguta growth and development. However, the mechanisms of how MYB proteins participate in freezing stress in A. arguta are still unclear. In this study, AaMYB16 was transformed into Arabidopsis thaliana and A. arguta. The relevant physiological and biochemical indexes were determined, and the regulatory model of AaMYB16 was preliminarily discussed. The results showed that there was an interaction between AaMYB16 and AabHLH137. AabHLH18 and AabHLH137 played a role in the upstream of AaMYB16. Overexpress AaMYB16 increased plant susceptibility to freezing stress, whereas silencing AaMYB16 enhanced freezing tolerance in A. arguta. Our results suggest that AaMYB16 is a negative regulator of freeze response in A. arguta. The AabHLH18/AabHLH137-AaMYB16 module plays an important role in freezing stress. These results provide insights into the molecular mechanism of low-temperature regulation of A. arguta, and a theoretical basis for fruit storage and breeding of A. arguta.

Agricultural soil cadmium (Cd) contamination severely endangers the growth and yield of oil crops. Castor bean meal (CBM) biofertilizer integrates microbial and organic fertilizer properties to regulate plant growth by improving the soil microbial environment and supplying essential nutrients to crops. However, the molecular mechanism underlying CBM-mediated alleviation of Cd toxicity in castor (Ricinus communis L.) remains unelucidated. This study aimed to elucidate the beneficial effects of 10 g & sdot;kg-1 CBM on alleviating Cd-induced toxicity (150 mg & sdot;kg-1 CdCl2 & sdot;2.5H2O) in 3-week-old castor seedlings. Through combined physiological, transcriptomic, and molecular analyses, exogenous CBM supply could enhance seedling growth by increasing chlorophyll accumulation, enhancing antioxidant system activity (encompassing enzymatic and non-enzymatic components), and reducing proline content. Additionally, transcriptomic analysis confirmed that genes involved in four key pathways-chlorophyll synthesis and degradation, proline metabolism, starch and sucrose metabolism, and the antioxidant system-play essential roles in CBM-mediated Cd resistance. Notably, the constructed castor gene regulatory network (CGRN) further identified key functional genes (e.g., SOD, POD, APX) and transcription factors (TFs; e.g., MYB, Trihelix, HD-ZIP families) that likely mediate CBM-alleviated Cd toxicity in castor. Collectively, these results shed light on the mechanisms by which CBM fertilizer ameliorates Cd phytotoxicity and provide a theoretical basis for optimizing phytoremediation strategies.

Rising atmospheric CO2 levels represent a major driver of global warming. Although CO2 is an essential substrate for plant photosynthesis, excessive levels can adversely impact photosynthesis and associated physiological and biochemical processes. Prunus mira Koehne, a resilient wild peach species variety known for its considerable adaptability, and high tolerance to abiotic stress. In this study, we investigated the physiological, biochemical, and stomatal response mechanisms of P. mira under high CO2 conditions. The results of our physiological and biochemical analyses revealed that elevated CO2 concentration inhibited the growth and development of P. mira. It also reduced chlorophyll content, impaired photosynthetic efficiency, and damaged PSII. Concurrently, high CO2 stimulated alternative respiration, disrupted membrane integrity, elevated ROS levels, and increased antioxidant enzyme activities. In guard cells, high CO2 triggered accumulations of ROS and NO, leading to stomatal closure, reduced stomatal conductance, and decreased transpiration. Moreover, Ca²⁺ and NR participated in the production of ROS and NO, respectively, while ASA promoted scavenging of excess H2O2. We also provide evidence that βcarbonic anhydrasemediated HCO3⁻ signaling, ROS buildup, and Ca2+channel activation contribute to stomatal regulation under high CO2. In summary, our study elucidates the multi-layered regulatory mechanisms underlying CO2-induced physiological and stomatal responses in plants, laying a groundwork for the selection and breeding of tree species adapted to climate change.

PEG-induced osmotic stress severely restricts strawberry growth and productivity. However, the molecular mechanisms underlying osmotic stress adaptation in wild strawberry germplasm resources remain insufficiently understood. In the present study, we comparatively investigated the physiological, transcriptomic, and metabolomic responses of cultivated octoploid strawberry (Fragaria & times; ananassa Duch.) (CS) and wild diploid strawberry (Fragaria nubicola Lindl.) (WS) collected from Medog County, Tibet, under PEG6000-induced osmotic stress. Physiological analyses demonstrated that osmotic stress markedly reduced net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), relative water content (RWC), and water use efficiency (WUE), while increasing reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) content in both strawberry species. Compared with the CS, the wild species exhibited more severe wilting, oxidative damage, and membrane lipid peroxidation, indicating greater sensitivity to osmotic stress. Integrated transcriptomic and metabolomic analyses revealed substantial differences in stress-responsive pathways between the two species. In CS, 896, 4591, and 6346 differentially expressed genes (DEGs) were identified under 5%, 10%, and 20% PEG treatments, respectively, whereas 3978, 977, and 1176 DEGs were identified in WS. DEGs were primarily enriched in peroxisome biogenesis, phytohormone signal transduction, glutathione metabolism, oxidative phosphorylation, and secondary metabolite biosynthesis pathways. Metabolomic profiling further demonstrated distinct regulation of phenylpropanoid metabolism, biosynthesis of phenylpropanoids, flavonoid biosynthesis, and the tricarboxylic acid (TCA) cycle. The CS preferentially regulated ABA- and cytokininassociated signaling pathways, whereas the WS exhibited enhanced ethylene-related responses and stronger accumulation of flavonoid metabolites. Importantly, the contrasting responses observed between the two strawberry species may also reflect differences in genome ploidy. CS likely possesses enhanced transcriptional buffering capacity, metabolic plasticity, and hormonal coordination compared with WS under osmotic stress conditions. Overall, this study provides new insights into the molecular mechanisms underlying osmotic stress adaptation in strawberry germplasm resources and offers valuable information for future drought-resistance breeding programs.

Drought significantly restricts the growth and quality of fruit trees Prunus mira, an ancient wild peach species, exhibits strong drought tolerance; however, the detailed response mechanism remains unknown. The nucleic acid excision repair factor radiation sensitivity 23d (Rad23d) plays a crucial role in plant stress, growth, and development. However, its specific mechanism of action in P. mira is unclear. Here, we report that PmRad23d positively contributes to the abscisic acid (ABA)-dependent drought response in P. mira. Overexpression of PmRad23d enhanced drought tolerance and ABA sensitivity, whereas inhibiting PmRad23d expression reduced the plant's drought tolerance and ABA sensitivity. PmRad23d was found to interact with the C2 domain at the N-terminus of PmSRC2 and PmCAR4, respectively. Together, they regulate the expression of ABA- and drought-related genes, activate ABA signaling, and induce stomatal closure, ultimately enhancing drought resistance in plants. Our findings shed light on the ABA-dependent drought response mechanism of PmRad23d, providing a basis for further exploration of drought tolerance in P. mira. Additionally, this study identifies potential candidate genes for enhancing peach germplasm resources and breeding drought-tolerant cultivars.

Drought stress limits the growth, development, and yield of castor. Brassinosteroid (BR)-signalling kinases (BSKs) play important roles in plant responses to abiotic stress. However, it is not yet clear which BSK gene is involved in the response of castor to drought stress. This study conducted an iTRAQ analysis of castor plant roots under 15 % PEG-6000-induced stress conditions and showed that RcBSK7 is a drought stress-responsive gene. Therefore, the function of the RcBSK7 gene in drought resistance was further investigated. Transgenic RcBSK7-overexpressing Arabidopsis and castor plants exhibited increased drought tolerance and antioxidant activity. Additionally, RcBSK7 overexpression under mannitol and abscisic acid (ABA) stress conditions promoted an increase in the number of Arabidopsis roots. Yeast two-hybrid assays and surface plasmon resonance (SPR) analysis revealed that RcBSK7 interacts with RcSAP3 and that RcSAP3, upon interaction with RcBSK7, positively influences drought resistance. Under drought stress, RcBSK7-overexpressing castor plants showed significantly increased expression of the key ABA biosynthetic enzymes NCED and AAO, leading to enhanced ABA accumulation. This study suggests that RcBSK7 positively regulates drought resistance by modulating the ABA signalling pathway, thereby increasing drought tolerance in plants. These findings reveal potential candidate genes for the molecular breeding of castor in response to drought stress.

In early spring, bleeding is a common occurrence in A. arguta when local temperatures reach 8 °C-10 °C. In this study, changes in the composition of bleeding sap and effect of bleeding on A. arguta were determined by analyzing the variation in the composition of bleeding sap from different periods. Accordingly, the bleeding sap was analyzed by gas chromatography-mass spectrometry (GC-MS), and the related physiological indexes in the stem were measured. The results revealed that in annual early spring, bleeding seriously affected A. arguta. In addition, annual branches had a stronger capacity for scavenging free radicals than biennial or barren branches. The metabolomics analysis identified a total of 153 differential metabolites, mainly involved in glycolysis and the tricarboxylic acid cycle. Bleeding decreased the number and length of new shoots and basal stems, as well as the size of the phloem, phloem fibers, and xylem. In contrast, the proline, soluble protein, soluble sugar, and malondialdehyde contents, as well as the activities of superoxide dismutase, catalase, and peroxidase, increased in treated stems compared with untreated controls. This study was the first to analyze the metabolomic profile of bleeding sap in A. arguta and investigate the effects of bleeding on its growth and development. The results will provide a theoretical basis for explaining the physiological changes occurring in stems after bleeding and lay a foundation for further research on understanding the underlying mechanism and repairing bleeding.

Banana (Musa spp.), a vital tropical fruit and food crop, faces significant challenges from cold and drought stress, which threaten its productivity. Uncovering the overlapping mechanisms of crop responses to abiotic stresses is essential for the development of multi-resistant crop varieties. This study investigates the overlapping response mechanisms of banana to cold and drought stress through integrated metabolomic and transcriptomic analyses. We conducted physiological assessments alongside these analyses to elucidate shared mechanisms. Our results showed that both cold and drought stress disrupted cell membrane stability and reduced relative water content and chlorophyll content in banana leaves. Metabolomic analysis identified 1800 annotated metabolites, with 636 and 405 differentially accumulated metabolites (DAMs) under cold and drought stress, respectively, and flavonoids represented the most abundant metabolite class. Transcriptomic analysis revealed that 5687 differentially expressed genes (DEGs) were induced under both stress conditions, with significant enrichment in pathways related to ascorbic acid, arginine, and proline metabolism. Integrating metabolomic and transcriptomic data highlighted carbohydrate, amino acid, and flavonoid metabolism as the central pathways shared in response to cold and drought stresses. Notably, while these pathways were common, specific structural genes and accumulated metabolites varied between stress types. Additionally, our results suggest that GDP-mannose is the primary ascorbate synthesis route under cold stress, whereas myo-inositol and galacturonic acid pathways dominate under drought stress. These findings enhance our understanding of banana's adaptive responses and provide a foundation for breeding multi-stress-resistant crop varieties in an era of climate change.

Global climate change exacerbates the effects of environmental stressors, such as drought, temperatures, salinity. Over the past two decades, there have been many studies on B-BOX PROTEINS (BBXs) in plants, with much of the research concentrated on their roles in plant growth and development. Nevertheless, recent findings have revealed that BBXs are also required for environmental stressors. In this review, we survey recent advances in the characterization BBXs of molecular mechanisms in abiotic stress tolerance and plant growth. The interaction between BBXs transcription factor and related proteins and the binding to promoter elements of stress response related genes were emphatic discussed. In addition, we discuss the future challenges and opportunities for extend the BBXs knowledge model plant to other species, and provide a better understanding of plant growth and development in natural conditions.

Seed germination is a pivotal period of plant growth and development. This process can be divided into four major stages, swelling absorption, seed coat dehiscence, radicle emergence and radicle elongation. Cupressus gigantea, a tree native to Tibet, China, is characterized by its resistance to stresses such as cold, and drought, and has a high economic and ecological value. Nevertheless, given its unique geographic location, its seeds are difficult to germinate. Therefore, it is crucial to explore the mechanisms involved in seed germination in this species to improve the germination efficiency of its seeds, thereby protecting this high-quality resource. Here, our findings indicate that seed germination was enhanced when exposed to a 6-h/8-h light/dark photoperiod, coupled with a temperature of 20 degrees C. Furthermore, the application of exogenous GA(3) (1 mg/ml, about 2.9 mM) stimulated the germination of C. gigantea seeds. Subsequently, proteomics was used to detect changes in protein expression during the four stages of seed germination. We identified 34 differentially expressed proteins (DEPs), including 13 at the radicle pre-emergence stage, and 17 at the radicle elongation stage. These DEPs were classified into eight functional groups, cytoskeletal proteins, energy metabolism, membrane transport, stress response, molecular chaperones, amino acid metabolism, antioxidant system and ABA signalling pathway. Most of them were found to be closely associated with amino acid metabolism. Combined, these findings indicate that, along with temperature and light, exogenous GA(3) can increase the germination efficiency of C. gigantea seeds. Our study also offers insights into the changes in protein expression patterns in C. gigantea seeds during germination.

Cupressus gigantea W. C. Cheng & L. K. Fu is an endemic conifer tree species that is distributed widely along the northern portion of the deep gorge of the Yarlung Tsangbo River on the Tibetan Plateau. However, as a key plant species growing on the Tibetan plateau, C. gigantea has since become an endangered species due to habitat loss and degradation, overexploitation, and other factors. It has been listed as a first-grade national protected wild plant species in China. Accordingly, to conserve this plant species, we should obtain more information on its genetic structure. In this study, the genetic diversity and structure among 67 samples were evaluated by the inter-simple sequence repeat (ISSR) technique. Overall, 78 bands were produced with a molecular length of 200 bp to 3100 bp using 10 ISSR primers. The mean values for the average number of alleles (Na), effective number of alleles (Ne), Nei's gene diversity (H), and Shannon's information index (I) were 1.529, 1.348, 0.199, and 0.293, respectively. Additionally, the number of polymorphic loci (NPLs) and percentage of polymorphic loci (PPLs) averaged 41.25 and 52.90, respectively. Further, total variation among populations was 14.2%, while that within populations was 85.8%; accordingly, the within-population genetic differentiation was found to be significant (p < 0.001). These results demonstrated that a genetic structure model with K = 3 fitted the data best, which agreed with the unweighted pair group method with arithmetic average (UPGMA) cluster and the principal coordinate analysis (PCoA). These findings are beneficial for ensuring the development and genetic protection of C. gigantea populations in the future.

The increase in atmospheric CO2 concentration is a significant factor in triggering global warming. CO2 is essential for plant photosynthesis, but excessive CO2 can negatively impact photosynthesis and its associated physiological and biochemical processes. The tetraploid Robinia pseudoacacia L., a superior and improved variety, exhibits high tolerance to abiotic stress. In this study, we investigated the physiological and proteomic response mechanisms of the tetraploid R. pseudoacacia under high CO2 treatment. The results of our physiological and biochemical analyses revealed that a 5% high concentration of CO2 hindered the growth and development of the tetraploid R. pseudoacacia and caused severe damage to the leaves. Additionally, it significantly reduced photosynthetic parameters such as Pn, Gs, Tr, and Ci, as well as respiration. The levels of chlorophyll (Chl a and b) and the fluorescent parameters of chlorophyll (Fm, Fv/Fm, qP, and ETR) also significantly decreased. Conversely, the levels of ROS (H2O2 and O2·−) were significantly increased, while the activities of antioxidant enzymes (SOD, CAT, GR, and APX) were significantly decreased. Furthermore, high CO2 induced stomatal closure by promoting the accumulation of ROS and NO in guard cells. Through a proteomic analysis, we identified a total of 1652 DAPs after high CO2 treatment. GO functional annotation revealed that these DAPs were mainly associated with redox activity, catalytic activity, and ion binding. KEGG analysis showed an enrichment of DAPs in metabolic pathways, secondary metabolite biosynthesis, amino acid biosynthesis, and photosynthetic pathways. Overall, our study provides valuable insights into the adaptation mechanisms of the tetraploid R. pseudoacacia to high CO2.

Abiotic stresses including cold, drought, salt, and iron deficiency severely impair plant development, crop productivity, and geographic distribution. Several bodies of research have shed light on the pleiotropic functions of BASIC HELIX-LOOP-HELIX (bHLH) proteins in plant responses to these abiotic stresses. In this review, we mention the regulatory roles of bHLH TFs in response to stresses such as cold, drought, salt resistance, and iron deficiency, as well as in enhancing grain yield in plants, especially crops. The bHLH proteins bind to E/G-box motifs in the target promoter and interact with various other factors to form a complex regulatory network. Through this network, they cooperatively activate or repress the transcription of downstream genes, thereby regulating various stress responses. Finally, we present some perspectives for future research focusing on the molecular mechanisms that integrate and coordinate these abiotic stresses. Understanding these molecular mechanisms is crucial for the development of stress-tolerant crops.

Actinidia arguta (A. arguta, kiwiberry) is a perennial deciduous vine with a strong overwintering ability. We hypothesized that trehalose metabolism, which plays a pivotal role in the stress tolerance of plants, may be involved in the cold acclimatization of A. arguta. Transcriptome analysis showed that the expression of AaTPPA, which encodes a trehalose-6-phosphate phosphatase (TPP), was upregulated in response to low temperatures. AaTPPA expression levels were much higher in lateral buds, roots, and stem cambia than in leaves in autumn. In AaTPPA-overexpressing (OE) Arabidopsis thaliana (A. thaliana), trehalose levels were 8–11 times higher than that of the wild type (WT) and showed different phenotypic characteristics from WT and OtsB (Escherichia coli TPP) overexpressing lines. AaTPPA-OE A. thaliana exhibited significantly higher freezing tolerance than WT and OtsB-OE lines. Transient overexpression of AaTPPA in A. arguta leaves increased the scavenging ability of reactive oxygen species (ROS) and the soluble sugar and proline contents. AaERF64, an ethylene-responsive transcription factor, was induced by ethylene treatment and bound to the GCC-box of the AaTPPA promoter to activate its expression. AaTPPA expression was also induced by abscisic acid. In summary, the temperature decrease in autumn is likely to induce AaERF64 expression through an ethylene-dependent pathway, which consequently upregulates AaTPPA expression, leading to the accumulation of osmotic protectants such as soluble sugars and proline in the overwintering tissues of A. arguta.

Background Trehalose is a nonreducing disaccharide containing two glucose molecules linked through an α,α-1,1-glycosidic bond. This unique chemical structure causes trehalose levels to fluctuate significantly in plants under stress, where it functions as an osmoprotectant, enhancing plant resistance to stress. Previous studies have confirmed that the trehalose synthesis pathway is widely conserved across most plants. However, the protective role of trehalose is limited only to organelles or tissues where the concentration is sufficiently high. Aim of review In this review, we summarize previous reports on improving plant stress tolerance (drought, cold, heat, salt, pathogen, etc.) by applying trehalose-6-phosphate (T6P) or trehalose and manipulating the expression of trehalose metabolism-related genes. The molecular mechanisms underlying T6P, trehalose, and their related genes that regulate plant stress resistance are reviewed. More progressive studies on the spatiotemporal control of trehalose metabolism will provide a novel tool that allows for the simultaneous enhancement of crop yield and stress tolerance. Key scientific concepts of review We introduce the history of trehalose and discuss the possibility of trehalose and its metabolity-related genes binding to T6P to participate in stress response through unknown signaling pathways. In addition, the effects of trehalose metabolism regulation on plant growth and stress resistance were reviewed, and the molecular mechanism was fully discussed. In particular, we came up with new insights that the molecular mechanism of trehalose metabolism to enhance plant stress resistance in the future and we propose the need to use biotechnology methods to cultivate crops with stress resistance and high yield potential.

The yield of castor is influenced by the type of inflorescence and the proportion of female flowers. However, there are few studies on the genetic mechanism involved in the development and differentiation of castor inflorescences. In this study, we performed transcriptomic analyses of three different phenotypes of inflorescences at the five-leaf stage. In comparison to the MI (complete pistil without willow leaves), 290 and 89 differentially expressed genes (DEGs) were found in the SFI (complete pistil with willow leaves) and the BI (monoecious inflorescence), respectively. Among the DEGs, 104 and 88 were upregulated in the SFI and BI, respectively, compared to the MI. In addition, 186 DEGs and 1 DEG were downregulated in the SFI and BI compared to the MI. Moreover, we conducted GO and KEGG enrichment analyses of the DEGs. In comparison to the MI, the SFI and BI exhibited the enrichment of functional branches in DEGs, specifically in pollen wall assembly, pollen development, and cellular component assembly involved in morphogenesis. In our study, RADL5 showed low expression levels between SFI-vs.-MI types. In addition, we found that the expression of NAC in the SFI differed from that in MI and BI, and some genes related to hormonal signaling changed their expression levels during inflorescence differentiation. These results reveal the genetic mechanism of sex genotypes in castor, which will not only guide researchers in the breeding of castor but also provide a reference for genetic research on other flowering plants.

Extreme environmental stress significantly impacts plant growth. Drought stress is one of the most important abiotic stresses, adversely affecting plant development and agricultural productivity. Prunus mira is an exceptionally drought-tolerant plant. However, there are a limited number studies on the drought resistance of it. Here, we isolated and identified nascent polypeptide-associated complex subunit alpha-like protein 1 of P. mira (PmNACA1). PmNACA1 comprises 201 amino acids and contains an NAC domain at its N-terminal. It was localized in the cytoplasm and nucleus. PmNACA1 was primarily expressed in leaves, and was induced by drought. PmNACA1 overexpression Arabidopsis thaliana increased germination and root elongation. Histochemical staining revealed that the overexpression lines accumulated less ROS under mannitol-induced osmotic stress. Under drought stress, overexpression lines exhibited an elevation in the activities of SOD, POD, CAT, and GR and a rise in the levels of GSH and GSSG. In addition, the overexpression lines exhibited relatively lower levels of H 2 O 2 , O 2 .− , MDA, and electrical conductivity than control plants. PmNACA1 induced the expression of drought- and ABA-related genes after drought treatment. PmNACA1 scavenged H 2 O 2 , DPPH radicals, and hydroxyl radicals in vitro. In summary, we conclude that PmNACA1 plays an active role in drought stress response by scavenging ROS.

BACKGROUND:Castor is an important industrial raw material. Drought-induced oxidative stress leads to slow growth and decreased yields in castor. However, the mechanisms of drought-induced oxidative stress in castor remain unclear. Therefore, in this study, physiological, biochemical, and RNA-seq analyses were conducted on the roots of castor plants under PEG-6000 stress for 3 d and 7 d followed by 4 d of hydration. RESULTS:The photosynthetic rate of castor leaves was inhibited under PEG-6000 stress for 3 and 7 d. Biochemical analysis of castor roots stressed for 3 d and 7 d, and rehydrated for 4 d revealed that the activities of APX and CAT were highest after only 3 d of stress, whereas the activities of POD, GR, and SOD peaked after 7 d of stress. RNA-seq analysis revealed 2926, 1507, and 111 differentially expressed genes (DEGs) in the roots of castor plants under PEG-6000 stress for 3 d and 7 d and after 4 d of rehydration, respectively. GO analysis of the DEGs indicated significant enrichment in antioxidant activity. Furthermore, KEGG enrichment analysis of the DEGs revealed significantly enriched metabolic pathways, including glutathione metabolism, fatty acid metabolism, and plant hormone signal transduction. WGCNA identified the core genes PP2C39 and GA2ox4 in the navajowhite1 module, which was upregulated under PEG-6000 stress. On the basis of these results, we propose a model for the response to drought-induced oxidative stress in castor. CONCLUSIONS:This study provides valuable antioxidant gene resources, deepening our understanding of antioxidant regulation and paving the way for further molecular breeding of castor plants.