Xishuangbanna (XIS) cucumber (Cucumis sativus) originated from low-altitude southwest China and shows extreme cold sensitivity. Nano-hydroxyapatite (nHAP), known for its high bioavailability and surface reactivity relative to bulk HAP, was applied to enhance the cold tolerance of XIS seedlings. We optimized fertilization timing and fertilizer concentration. By determining physiological parameters alongside gene expression profiling and transcriptomic analysis, we preliminarily dissected the physiological and molecular mechanisms underlying nHAP-enhanced chilling tolerance. nHAP application preserved free and bound water even at 24 h into the cold-stress treatment, as detected by nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). Exposure to cold stress caused a chilling injury index (CII) of 73.33%, while foliar spraying of nHAP at gradient concentration reduced CII values by 9.09-54.55%. At the same time, electrolyte leakage and malondialdehyde content were decreased by 6.68-61.41% and 12.92-67.16% respectively; chlorophyll content increased by 0.01-73.42%; SOD, POD, and soluble protein content increased by 10.54-161.53%, 16.50-154.33%, and 2.03-63.26%, respectively. Soil application of nHAP showed a similar but weaker effect than foliar spraying on alleviating chilling injury, and the optimal concentration was 1000 mg/L. Quantitative Real-Time PCR (qRT-PCR) revealed that foliar spraying of nHAP upregulated the gene expression of Superoxide dismutase genes (CsCu/ZnSOD and CsMnSOD) and major facility superfamily genes (CsSPX-MFS1 and CsSPX-MFS2) in the cold treatment. We then profiled the transcriptome changes in seedling leaves during the cold treatment after foliar spraying of nHAP. Without nHAP application, cold stress resulted in a total of 6795 differentially expressed genes (DEGs), which were functionally enriched in plant-pathogen interaction and plant hormone signal transduction pathways. Under nHAP application, cold stress only caused 776 DEGs, which were functionally enriched in plant hormone signal transduction and galactose metabolism. These findings suggest that nHAP could improve the cold tolerance of cucumber seedlings through boosting antioxidant activity and plant hormone signaling pathways.

Low-temperature stress is a major environmental constraint, limiting the growth, development, and yield of peppers. Cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POA) are two key enzymes in lignin synthesis, participating in monolignol biosynthesis and monolignol polymerization, respectively. Although CAD and POA are known to play central roles in lignin biosynthesis and plant responses to abiotic stress, their functions in peppers remain poorly understood. In this study, we demonstrated the interaction between CaCAD1 and CaPOA1, which collectively positively regulated lignin biosynthesis in peppers. Additionally, CaCAD1 and CaPOA1 expression was induced by low temperatures, with expression levels gradually increasing with prolonged cold treatment. Silencing of CaCAD1 or CaPOA1 increased the sensitivity of pepper plants to low temperatures. On the other hand, overexpression of CaCAD1 and CaPOA1 in Arabidopsis enhanced its reactive oxygen species scavenging ability and improved plant tolerance to freezing conditions. In summary, the CaCAD1-CaPOA1 module was shown to play a crucial role in pepper cold tolerance, providing valuable insights and targets for future molecular breeding efforts aimed at enhancing pepper cold tolerance.

BACKGROUND:The cucumber (Cucumis sativus) is a model species for genomic studies in vegetables due to its relatively small genome size. Long non-coding RNAs (lncRNAs) play crucial roles in plant growth, development, and stress responses. LncRNAs are less conserved among plant species and comparative genomic study of lncRNA in cucumbers can provide new insight about the evolution and function of cucumber lncRNAs. RESULTS:Here, full-length transcriptome sequencing was applied to identify high-confidence lncRNAs in wild (C. sativus var. hardwickii) and semi-wild (C. sativus var. xishuangbannanensis) cucumbers. A total of 1,598 lncRNAs were screened out, and these lncRNAs exhibit distinct characteristics, including fewer exons, shorter sequences, and lower GC content when compared with messenger RNAs (mRNAs). We observed a slight expansion of lncRNAs, such as lncRNA family 1, which could contain up to 21 members distributed across different chromosomes. These family members are typically derived from the same genomic region, likely as a result of alternative splicing. Differentially expressed lncRNAs (DELs) may cis-regulate the expression of nearby genes, and functional enrichment analysis indicated that the primary biological process involved was environmental adaptation. We predicted that eighteen lncRNAs could serve as microRNA (miRNA) precursors, generating 25 miRNAs, which subsequently target 1,628 protein-coding genes. Functional enrichment analysis revealed that these target genes were primarily enriched in epigenetic regulatory pathways, suggesting a complex feedback regulation involving epigenetic modifications and gene expression. The competing endogenous RNA (ceRNA) network analysis revealed that 31 lncRNAs interacted with 26 miRNAs and competed for 134 targeted protein-coding genes. MiR156 plays a crucial role in the ceRNA network, competing with CsLncRNA94 to target the 7 members of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factor gene family. We observed that CsLncRNA94 participates in the miR156-SPL module's response to light and low temperature and acts as a negative regulator of cold tolerance in cucumber, as demonstrated through transient expression in cotyledons. CONCLUSIONS:Full-length lncRNAs were identified in wild- and semi-wild cucumbers. The differential expression of lncRNAs between cucumbers with different domestication degree is likely for environmental adaptation particularly via lncRNA-miRNA pathway. CsLncRNA94 is a representative lncRNA that regulate miR156-SPL module in response to light and temperature stimuli. CLINICAL TRIAL NUMBER:Not applicable.

Low temperature restricts the growth, development, and yield of peppers, significantly limiting the development of the pepper industry. NAC (NAM, ATAF1/2, and CUC2) transcription factors (TFs) are implicated in plant responses to cold stress, but their specific mechanisms in peppers are unclear. In this study, we isolated a cold-induced NAC transcription factor, CaNAC76, from pepper (Capsicum annuum L.). CaNAC76 is localized in the nucleus and cytoplasm and exhibits transcriptional activation activity. Silencing CaNAC76 expression reduced the activities of superoxide dismutase, peroxidase, and catalase enzymes, resulting in decreased cold tolerance in peppers. Conversely, overexpressing CaNAC76 increased the activities of antioxidant enzymes and the expression of cold stress-responsive genes (ICE-CBF-COR) in Arabidopsis, enhancing the plant's freezing tolerance. Transcriptional regulation analysis showed that CaNAC76 directly binds to the promoter region of CaCAD1 and induces its expression. Similarly, low temperatures induced the expression of CaCAD1. Ectopic expression of CaCAD1 improved Arabidopsis freezing tolerance, whereas silencing CaCAD1 expression increased sensitivity to low temperatures. Furthermore, we observed that CaNAC76 overexpression enhanced CAD activity and lignin content in Arabidopsis, leading to lignin deposition in the xylem and interfascicular fibers. In summary, the results demonstrate that CaNAC76 can enhance cold tolerance in peppers by affecting both CBF-dependent (ICE-CBF-COR) and CBF-independent pathways (promoting CaCAD1 expression).

The most widely used rootstock of cucumber grafting is pumpkin (Cucurbita moschata). The main task of pumpkin rootstock breeding is to evaluate its compatibility with cucumber scions. One of the main factors affecting grafting compatibility is the rootstock bleeding sap, which affects the wound healing of graft junction. We evaluated the grafting affinity of 30 pumpkin rootstocks, which were F1 hybrids derived from 56 breeding lines, by grafting them with the cucumber scion FH8. Correlation analysis of grafting compatibility with phenotypic traits of rootstock seedlings, grafted plants, and biochemical characteristics of rootstock bleeding sap highlighted the positive role of soluble solids content and the negative role of the absorbance of bleeding sapsmeasured at multiple wavelengths (from 280 nm to 700 nm). Bleeding saps from three rootstocks (RS50, RS83, and RS55) with different grafting compatibility were assayed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The predominant content in bleeding saps was amino acids. Compared with self-rooted-grafting, intergeneric grafting caused changes in the pathways associated with “abiotic stress responses”, “ribosome” and “plant hormone signal transduction” in integrated transcriptomic and metabolic analysis. When compared with the bleeding sap of RS50 (BS-RS50) with low grafting compatibility, BS-RS55 with high grafting compatibility contained much lower content of flavonoids such as nicotiflorin, lonicerin, isoquercitrin and isovitexin. A similar difference profile of these flavonoids was not observed in cucumber scions, although flavonoid pathway was also affected by grafting in scions. Pumpkin rootstocks show a big variation in grafting compatibility with cucumbers scions, which at least partially depends on the nutrients (bleeding saps) transported from rootstocks to scions. Flavonoids play a negative role in pumpkin-cucumber grafting compatibility.

Common bean (Phaseolus vulgaris L.) is a thermophilic crop, and exposure to cold stress can significantly impact their yield and quality. To elucidate the impact of cold stress on cold-tolerant ‘Wei Yuan’ (WY) and cold-sensitive ‘Bai Bu Lao’ (BBL) of common bean, the mechanism of cold tolerance was studied by physiological and biochemical and multi-omics analysis. In this study, lower relative conductivity and higher malondialdehyde content after cold stress endowed ‘WY’ seedlings with cold tolerance. A total of 11,837 differentially expressed genes (DEGs) and 923 differential metabolites (DEMs) were identified by transcriptome and metabolomics analysis. Joint analysis showed that under cold stress, DEGs and DEMs in common beans are extensively engaged in sugar, amino acid and isoflavonoid biosynthesis, flavone and flavonol biosynthesis, and plant hormone signal translation, especially related to isoflavone biosynthesis. In addition, it was also found that bHLH and MYB family transcription factors may be involved in the cold signal transduction of common bean. The above results will provide a theoretical basis for the cold tolerance mechanism of common beans and provide help for the screening of cold-tolerant resources of common beans. Not applicable.

Xishuangbanna (XIS) cucumber (Cucumis sativus L. var. xishuangbannanesis) is a semiwild variety originating from low latitude tropic areas, and therefore shows extreme cold sensitivity and heat tolerance. Here, we mapped the quantitative trait loci (QTLs) that control the cold sensitivity and heat tolerance of XIS cucumber seedlings. Using bulked segregant analysis (BSA), we identified three QTLs (HTT1.1, HTT3.1, and HTT3.2, with a total length of 11.98 Mb) for heat tolerance and two QTLs (LTT6.1 and LTT6.2, with a total length of 8.74 Mb) for cold sensitivity. The QTL LTT6.1 was then narrowed down to a length of 641 kb by using kompetitive allele-specific PCR (KASP) markers. Based on structural variants (SVs) and single-nucleotide polymorphisms (SNPs), we found the LTT6.1 is covered by a high divergent region including a 50 kb deletion in the XIS49 genome, which affects the gene structure of lipase abhydrolase domain containing 6 (ABHD6, Csa_6G032560). Accordingly, there is a very big difference in lipid composition, but not in other osmoprotectants like free amino acids and fatty acids, between XIS49 and cultivated cucumber CL. Moreover, we calculated the composite likelihood ratio (CLR) and identified selective sweeps from 115 resequencing data, and found that lipid- and fatty-acid-related processes are major aspects in the domestication of the XIS group cucumber. LTT6.1 is a particularly special region positioned nearby lipid-related selective sweeps. These studies above suggested that the lipid-related domestication of XIS cucumbers should account for their extreme cold sensitivity.

Vegetables, as indispensable non-staple foods in people’s daily diet, provide a variety of essential vitamins, minerals, and other nutrients, as well as special phytochemicals, which are recognized as functional components for human nutritional balance or medicinal purposes [...]

Cold temperatures negatively impact crop yield and quality, posing significant limitations to the advancement of the vegetable industry. MYB transcription factors are pivotal in enhancing plant resilience against various abiotic stresses, including low-temperature stress. Pepper (Capsicum annuum L.) is a nutrient-rich vegetable crop sensitive to low temperatures. This study aimed to determine the function of CaMYB80 in the cold stress response of pepper through virus-induced silencing. The study also conducted heterologous expression of CaMYB80 in Arabidopsis and tomato plants. The results showed that CaMYB80 could respond to low-temperature stress in pepper. CaMYB80 was localized in the nucleus and cytoplasm and exhibited transcriptional activation ability. Moreover, CaMYB80 silencing decreased cold tolerance in pepper, while its heterologous overexpression increased cold tolerance in Arabidopsis and tomato. Further analysis showed that CaMYB80 interacted with CaPOA1 (peroxidase N1-like). Similarly, the expression of CaPOA1 also responded to low-temperature stress. Overexpression of CaPOA1 enhanced freezing tolerance in Arabidopsis, while its silencing reduced cold stress tolerance in pepper. Furthermore, overexpression of CaMYB80 in Arabidopsis and tomato could increase the activity of peroxidases and the expression levels of genes in the ICE-CBF-COR (inducer of CBF expression, C-repeat binding factor, cold-responsive) regulatory network. In conclusion, our research results indicate that CaMYB80 enhances pepper cold tolerance by interacting with CaPOA1 to increase peroxidase activity and influence the expression of ICE-CBF-COR related genes.

Environmental factors such as light and temperature tightly regulate plant flowering time. Under stressful conditions, plants inhibit vegetative growth and accelerate flowering as an emergency response. This adaptive mechanism benefits the survival of species and enhances their reproductive success. This phenomenon is often referred to as stress escape. However, the signaling pathways between low-temperature signals and flowering time are poorly understood. In this study, the MIKC transcription factor, CaSOC1, was isolated from pepper (Capsicum annuum), which showed suppressed expression under low-temperature conditions. Silencing the expression of CaSOC1 in pepper plants resulted in reduced photosynthetic capacity, inhibited vegetative growth, and increased sensitivity to low temperatures. In contrast, overexpression of CaSOC1 increased the biomass of tomato plants under normal growth conditions but suppressed their antioxidant enzyme activity at low temperatures, which negatively regulated their cold tolerance. Furthermore, intermittent low-temperature treatment with CaSOC1 overexpression promoted early flowering in tomato plants. Our findings demonstrate that CaSOC1 reduced the cold tolerance of pepper plants under short-term low-temperature conditions, whereas intermittent low-temperature treatment enhanced flower bud differentiation, enabling stress escape and adaptation to long low-temperature environments.

Background The mediator complex subunits (MED) constitutes a multiprotein complex, with each subunit intricately involved in crucial aspects of plant growth, development, and responses to stress. Nevertheless, scant reports pertain to the VunMED gene within the context of asparagus bean ( Vigna unguiculata ssp. sesquipedialis ). Establishing the identification and exploring the responsiveness of VunMED to cold stress forms a robust foundation for the cultivation of cold-tolerant asparagus bean cultivars. Results Within this study, a comprehensive genome-wide identification of VunMED genes was executed in the asparagus bean cultivar 'Ningjiang3', resulting in the discovery of 36 distinct VunMED genes. A phylogenetic analysis encompassing 232 MED genes from diverse species, including Arabidopsis , tomatoes, soybeans, mung beans, cowpeas, and asparagus beans, underscored the highly conserved nature of MED gene sequences. Throughout evolutionary processes, each VunMED gene underwent purification and neutral selection, with the exception of VunMED19a . Notably, VunMED9/10b/12/13/17/23 exhibited structural variations discernible across four cowpea species. Divergent patterns of temporal and spatial expression were evident among VunMED genes, with a prominent role attributed to most genes during early fruit development. Additionally, an analysis of promoter cis-acting elements was performed, followed by qRT-PCR assessments on roots, stems, and leaves to gauge relative expression after exposure to cold stress and subsequent recovery. Both treatments induced transcriptional alterations in VunMED genes, with particularly pronounced effects observed in root-based genes following cold stress. Elucidating the interrelationships between subunits involved a preliminary understanding facilitated by correlation and principal component analyses. Conclusions This study elucidates the pivotal contribution of VunMED genes to the growth, development, and response to cold stress in asparagus beans. Furthermore, it offers a valuable point of reference regarding the individual roles of MED subunits.

The Xishuangbanna (XIS) cucumber (Cucumis sativus var. xishuangbannanesis) is a semiwild variety that has many distinct agronomic traits. Here, long reads generated by Nanopore sequencing technology helped assembling a high-quality genome (contig N50 = 8.7 Mb) of landrace XIS49. A total of 10,036 structural/sequence variations (SVs) were identified when comparing with Chinese Long (CL), and known SVs controlling spines, tubercles, and carpel number were confirmed in XIS49 genome. Two QTLs of hypocotyl elongation under low light, SH3.1 and SH6.1, were fine-mapped using introgression lines (donor parent, XIS49; recurrent parent, CL). SH3.1 encodes a red-light receptor Phytochrome B (PhyB, CsaV3_3G015190). A similar to 4 kb region with large deletion and highly divergent regions (HDRs) were identified in the promoter of the PhyB gene in XIS49. Loss of function of this PhyB caused a super-long hypocotyl phenotype. SH6.1 encodes a CCCH-type zinc finger protein FRIGIDA-ESSENTIAL LIKE (FEL, CsaV3_6G050300). FEL negatively regulated hypocotyl elongation but it was transcriptionally suppressed by long terminal repeats retrotransposon insertion in CL cucumber. Mechanistically, FEL physically binds to the promoter of CONSTITUTIVE PHOTOMORPHOGENIC 1a (COP1a), regulating the expression of COP1a and the downstream hypocotyl elongation. These above results demonstrate the genetic mechanism of cucumber hypocotyl elongation under low light. Structural variation in quantitative trait loci affects hypocotyl elongation in Xishuangbanna cucumber.

Cold is an important environmental limiting factor affecting plant yield and quality. Capsicum (chili pepper), a tropical and subtropical vegetable crop, is extremely sensitive to cold. Although H2S is an important signaling regulator in the responses of plant growth and development to abiotic stress, few studies have examined its effects on cold-sensitive capsicum varieties. Through biotechnology methods to enhance the cold resistance of peppers, to provide some reference for pepper breeding, investigated molecular regulation by H2S of responses to cold stress in cold-sensitive capsicum plants, via physiological and transcriptomic analyses. In capsicum seedlings, exogenous H2S enhanced relative electrical conductivity (REC) and levels of malondialdehyde (MDA) under cold stress, maintained membrane integrity, increased the activity of enzymatic and non-enzymatic antioxidants, balanced reactive oxygen species levels (O2·− and H2O2), and improved photosynthesis, mitigating the damage caused by cold. In addition, 416 differentially expressed genes (DEGs) were involved in the response to cold stress after H2S treatment. These DEGs were mainly enriched in the ascorbate–glutathione and starch–sucrose metabolic pathways and plant hormone signal-transduction pathways. Exogenous H2S altered the expression of key enzyme-encoding genes such as GST, APX, and MDHAR in the ascorbate–glutathione metabolism pathway, as well as that of regulatory genes for stimulatory hormones (auxin, cytokinins, and gibberellins) and inhibitory hormones (including jasmonate and salicylic acid) in the plant hormone signal-transduction pathway, helping to maintain the energy supply and intracellular metabolic stability under cold stress. These findings reveal that exogenous H2S improves cold tolerance in cold-sensitive capsicum plants, elucidating the molecular mechanisms underlying its responses to cold stress. This study provides a theoretical basis for exploring and improving cold tolerance in capsicum plants.

Xishuangbanna (XIS) cucumber is a semi-wild cucumber originating from a low latitude. XIS cucumbers are strictly short-day plants, while cultivated cucumbers are day-neutral plants. The length of the light phase has a dosage effect on flowering time and the day length requirement for flowering is 8-11.5 h. Out-of-range photoperiod conditions and weak light conditions are unfavorable for blooming. Transcriptomic and gene expression analysis indicate circadian pathway genes as well as CONSTANS (CO) did not show a differential response to photoperiod treatment between XIS and cultivated cucumbers. The FLOWERING LOCUST (FT) gene is activated from 10:00 to 18:00, and long- (16 h) and medium- (12 h) day length suppressed this diurnal rhythm expression. We designed Kompetitive allele specific PCR (KASP) markers based on genomic SNPs between the mapping parents (XIS49 and CL) to genetically map the short-day flowering gene. Field investigation was performed after long-day photoperiod (16 h) treatment. Finally, we detected a strong quantitative trait locus (QTL) signal at a 540-kb segment (chr1: 29.08-29.62 Mb) that carries the FT gene. We found a 30-kb TE-rich insertion with a distance of 15 kb to the FT gene in XIS49, which may contribute to the gain of the short-day flowering trait in XIS49. The 30-kb insertion endowed the FT gene and the inserted polygalacturonase (PG) gene with a photoperioddependent expression manner. Our study indicates that the FT gene, but not its upstream circadian clock genes, regulate short-day flowering in the XIS cucumber, and the cis-regulation of the FT gene is probably due to a TE insertion.

Low-temperature stress in early spring seriously affects the growth and development of cowpea seedlings. To study the alleviative effect of the exogenous substances nitric oxide (NO) and glutathione (GSH) on cowpea (Vigna unguiculata (Linn.) Walp.) seedlings under 8 °C low-temperature stress, 200 μmol·L−1 NO and 5 mmol·L−1 GSH were sprayed on cowpea seedlings whose second true leaf was about to unfold to enhance the tolerance of cowpea seedlings to low temperature. Spraying NO and GSH can eliminate excess superoxide radicals (O2−) and hydrogen peroxide (H2O2) to varying degrees, reduce the content of malondialdehyde and relative conductivity, delay the degradation of photosynthetic pigments, increase the content of osmotic regulating substances such as soluble sugar, soluble protein, and proline, and improve the activity of antioxidant enzymes such as superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, dehydroascorbate reductase, and monodehydroascorbate reductase. This study revealed that the mixed use of NO and GSH played an important role in alleviating low temperature stress, and the effect of spraying NO alone was better than that of spraying GSH.

Triadimefon is a typical systemic fungicide that is widely used in the management of powdery mildew, rust disease, and southern blight. In this study, we measured fungicide residue to profile its absorption, translocation, and accumulation in three representative vegetable crops (Pak choi, cucumber, and pepper) after over-application. The fungicides were applied through entire-plant spraying (EPS), root-irrigation (RI), and middle-leaf-daubing (MLD). The half-life of triadimefon depends on the application method and plant species. In EPS, the half-life was 5.42 days (Pak choi), 6.86 days (cucumber), and 6.73 days (pepper), while in RI it was 4.39 days (Pak choi), 6.30 days (cucumber), and 5.98 days (pepper). In the EPS treatment, triadimefon is translocated both upward/outside and downward/inner-side from the daubed leaves in all the three vegetable crops. The transfer amount to each organ reached a peak on the 2nd day after fungicide application. The mesophyll of Pak choi exhibited a higher fungicide deposition compared to the petiole. In cucumber and pepper, the leaves demonstrated the highest accumulation of triadimefon (approximately 0.3–0.5 mg·kg−1), followed by stems. Roots and fruits displayed the lowest levels of triadimefon accumulation. Furthermore, triadimefon was found to have an impact on chlorophyll content, root activity, as well as the activity of superoxide dismutase and catalase in Pak choi, indicating its potential as a plant growth regulator. These aforementioned studies provide novel insights for the safe and efficient application of triadimefon in the production of Pak choi, cucumber, and pepper.

Blackleg disease is devastating for wasabi (Eutrema japonicum) production, occurring at any time and everywhere within the main production area of the Sichuan Province, China. There have been very few studies on the chemical control of this disease. In this study, we isolated and identified a local popular strain of the pathogen Plenodomus wasabiae. The isolated fungus strain caused typical disease spots on the leaves and rhizomes upon inoculation back to wasabi seedlings. The symptoms of blackleg disease developed very quickly, becaming visible on the second day after exposure to P. wasabiae and leading to death within one week. We then evaluated the efficacy of ten widely used fungicides to screen out effective fungicides. The efficacy of the tested fungicides was determined through mycelial growth inhibition on medium plates. As a result, tebuconazole and pyraclostrobin were able to inhibit the mycelial growth of P. wasabiae, and the most widely used dimethomorph in local production areas produced the lowest inhibition activity (13.8%). Nevertheless, the highest control efficacy of tebuconazole and pyraclostrobin on wasabi seedlings was only 47.48% and 39.03%, respectively. Generally, the control efficacy of spraying the fungicide before inoculation was better than that after inoculation. An increase in the application concentration of the two fungicides did not proportionately result in improved performance. We cloned the full-length sequence of sterol 14-demethylase (CYP51) and cytochrome B (CYTB) of which the mutations may contribute to the possible antifungalresistance. These two genes of the isolated fungus do not possess any reported mutations that lead to fungicide resistance. Previous studies indicate that there is a significant difference between fungicides in terms of the effectiveness of controlling blackleg disease; however, the control efficacy of fungicides is limited in blackleg control. Therefore, field management to prevent wound infection and unfavorable environmental conditions are more important than pesticide management.

Spermidine synthase (SPDS) is a key enzyme in the polyamine anabolic pathway. SPDS genes help regulate plant response to environmental stresses, but their roles in pepper remain unclear. In this study, we identified and cloned a SPDS gene from pepper (Capsicum annuum L.), named CaSPDS (LOC107847831). Bioinformatics analysis indicated that CaSPDS contains two highly conserved domains: an SPDS tetramerisation domain and a spermine/SPDS domain. Quantitative reverse-transcription polymerase chain reaction results showed that CaSPDS was highly expressed in the stems, flowers, and mature fruits of pepper and was rapidly induced by cold stress. The function of CaSPDS in cold stress response was studied by silencing and overexpressing it in pepper and Arabidopsis, respectively. Cold injury was more serious and reactive oxygen species levels were greater in the CaSPDS-silenced seedlings than in the wild-type (WT) seedlings after cold treatment. Compared with the WT plants, the CaSPDS-overexpression Arabidopsis plants were more tolerant to cold stress and showed higher antioxidant enzyme activities, spermidine content, and cold-responsive gene (AtCOR15A, AtRD29A, AtCOR47, and AtKIN1) expression. These results indicate that CaSPDS plays important roles in cold stress response and is valuable in molecular breeding to enhance the cold tolerance of pepper.

Low-temperature stress is a key factor limiting the yield and quality of the common bean. 5-aminolevulinic acid (5-ALA), an antioxidant in plants, has been shown to modulate plant cold stress responses. However, the molecular mechanisms of 5-ALA-induced physiological and chemical changes in common bean seedlings under cold stress remains unknown. This study explored the physiological and transcriptome changes of common bean seedlings in response to cold stress after 5-ALA pretreatment. Physiological results showed that exogenous 5-ALA promotes the growth of common bean plants under cold stress, increases the activity of antioxidant enzymes (superoxide dismutase: 23.8%; peroxidase: 10.71%; catalase: 9.09%) and proline content (24.24%), decreases the relative conductivity (23.83%), malondialdehyde (33.65%), and active oxygen content, and alleviates the damage caused by cold to common bean seedlings. Transcriptome analysis revealed that 214 differentially expressed genes (DEGs) participate in response to cold stress. The DEGs are mainly concentrated in indole alkaloid biosynthesis, carotenoid biosynthesis, porphyrin, and chlorophyll metabolism. It is evident that exogenous 5-ALA alters the expression of genes associated with porphyrin and chlorophyll metabolism, as well as the plant hormone signal transduction pathway, which helps to maintain the energy supply and metabolic homeostasis under low-temperature stress. The results reveal the effect that applying exogenous 5-ALA has on the cold tolerance of the common bean and the molecular mechanism of its response to cold tolerance, which provides a theoretical basis for exploring and improving plant tolerance to low temperatures.