Low Temperature Stress Research Articles

Transcriptomic and Physiological Studies Unveil that Brassinolide Maintains the Balance of Maize's Multiple Metabolisms under Low-Temperature Stress.

Low-temperature (LT) is one of the major abiotic stresses that restrict the growth and development of maize seedlings. Brassinolides (BRs) have been shown to enhance LT tolerance in several plant species; the physiological and molecular mechanisms by which BRs enhance maize tolerance are still unclear. Here, we characterized changes in the physiology and transcriptome of N192 and Ji853 seedlings at the three-leaf stage with or without 2 μM 2,4-epibrassinolide (EBR) application at 25 and 15 °C environments via high-performance liquid chromatography and RNA-Sequencing. Physiological analyses revealed that EBR increased the antioxidant enzyme activities, enhanced the cell membrane stability, decreased the malondialdehyde formation, and inhibited the reactive oxygen species (ROS) accumulation in maize seedlings under 15 °C stress; meanwhile, EBR also maintained hormone balance by increasing indole-3-acetic acid and gibberellin 3 contents and decreasing the abscisic acid level under stress. Transcriptome analysis revealed 332 differentially expressed genes (DEGs) enriched in ROS homeostasis, plant hormone signal transduction, and the mitogen-activated protein kinase (MAPK) cascade. These DEGs exhibited synergistic and antagonistic interactions, forming a complex LT tolerance network in maize. Additionally, weighted gene co-expression network analysis (WGCNA) revealed that 109 hub genes involved in LT stress regulation pathways were discovered from the four modules with the highest correlation with target traits. In conclusion, our findings provide new insights into the molecular mechanisms of exogenous BRs in enhancing LT tolerance of maize at the seedling stage, thus opening up possibilities for a breeding program of maize tolerance to LT stress.

Development of eco-friendly and high-content rubberized asphalt modified by waste cooking oil desulfurized crumb rubber and waste crumb rubber

To conserve non-renewable petroleum-based asphalt resources and address the limitations of incorporating high-content waste crumb rubber (CR) in conventional crumb rubber modified asphalt (CRMA), this study examines the feasibility of utilizing waste cooking oil desulfurized crumb rubber (ODR) in conjunction with CR to prepare high-content rubberized asphalt (HCRA). The basic, chemical, rheological, and asphalt-aggregate adhesion properties of HCRA, both with and without a small quantity of styrene-butadiene-styrene (SBS) copolymer modifier, were evaluated using infrared spectroscopy (FTIR), dynamic shear rheometer (DSR), bending beam rheometer (BBR), asphalt-aggregate pull-off test, contact angle test, and atomic force microscopy (AFM). The results showed that the modification involving ODR and CR primarily constitutes a physical process, rather than a chemical reaction, as evidenced by the lack of new functional groups. Similarly, the addition of an SBS modifier predominantly results in physical modifications accompanied by minor chemical interactions. The improved desulfurization degree of ODR diminishes the elastic stiffening effect of CR on the matrix asphalt at the high-temperature (low-frequency) domain and reduces adhesion properties between HCRA and aggregates, while enhancing the flexibility of HCRA at the low-temperature (high-frequency) domain. The inclusion of a small quantity of SBS modifier allows HCRA to demonstrate high-temperature performance and adhesion properties on par with CRMA, alongside superior low-temperature stress relaxation, phase stability, storage stability, and water damage resistance. These attributes indicate that the HCRA with a small quantity of SBS modifier has a broader service temperature range compared to CRMA. This study achieves approximately 33.3 % replacement of asphalt materials while preserving the performance of rubberized asphalt.

AmDEF2.7, a tandem duplicated defensin gene from Ammopiptanthus mongolicus, activated by AmWRKY14, enhances the tolerance of Arabidopsis to low temperature and osmotic stress

Ammopiptanthus mongolicus is an evergreen broad-leaved shrub growing in temperate regions. Plant defensins, a type of cysteine-rich small peptides, contribute to plant defense as antimicrobial peptides. In this study, we analyzed the evolution and expression patterns of the defensin gene family in A. mongolicus, and explored the function and regulatory mechanisms of the AmDEF2.7 gene in response to abiotic stress. Seven out of ten defensin genes had undergone segmental duplication and tandem duplication, especially, AmDEF2.6, AmDEF2.7, and AmDEF2.8, which were clustered on chromosome 9. The expression of multiple defensin genes was responsive to abiotic stress, with three defensin genes, including AmDEF2.7, showing significant induction during winter. Yeast expressing AmDEF2.7 gene exhibited increased resistance to freeze-thaw cycles and osmotic stress, while transgenic Arabidopsis overexpressing the AmDEF2.7 showed improved tolerance to both freezing and drought conditions. Furthermore, AmWRKY14 bound to the AmDEF2.7 gene promoter, and activated the expression of AmDEF2.7. These results highlighted the role of defensin AmDEF2.7 in the adaptation of A. mongolicus to temperate winter climate. This study expands our knowledge of plant defensin and provides support for clarifying the molecular mechanism of the adaptation of A. mongolicus to winter climate.

Integrated transcriptomic and epigenomic analyses to disclose the transcriptional regulatory mechanisms of lipid and energy metabolism under cold stress in grass carp

Cold-induced injuries significantly restrict the potential and efficacy of suivival and growth, necessitating a deeper understanding of cold response in ectothermic fish. Understanding the mechanisms by which fish respond to low-temperature stress has thus become a critical research focus in aquaculture. This study aims to investigate the effects of different temperature gradients (28 °C, 10 °C, and 2 °C) on global gene transcription in grass carp Ctenopharyngodon idellus. Additionally, the study examines cold-induced chromatin accessibility and transcriptional regulation through an integration of RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin using sequencing (ATAC-seq) analyses. Transcriptome analysis revealed that mitochondrial damage and endoplasmic reticulum stress are major factors contributing to grass carp mortality under cold stress. The dataset also disclosed hepatocyte nuclear factor 1 beta (Hnf1b) and peroxisome proliferator-activated receptor alpha (PPARa) as key transcription factors for lipid and energy metabolism in grass carp under cold stress. Notably, Hnf1b and PPARa form a complex transcriptional regulatory network with other transcription factors, decreasd binding activity inactivates the expression of genes related to lipid and energy metabolism under cold stress. These results highlight the transcriptional regulation of lipid and energy metabolism in response to cold stress in grass carp. Overall, this study enhances our understanding of low-temperature response mechanisms in grass carp, providing valuable insights for further investigations.

Systematic Analysis of the BrHAT Gene Family and Physiological Characteristics of Brassica rapa L. Treated with Histone Acetylase and Deacetylase Inhibitors under Low Temperature.

Brassica rapa L. is an important overwintering oilseed crop in Northwest China. Histone acetyltransferases (HATs) play an important role in epigenetic regulation, as well as the regulation of plant growth, development, and responses to abiotic stresses. To clarify the role of histone acetylation in the low-temperature response of B. rapa L., we identified 29 HAT genes in B. rapa L. using bioinformatics tools. We also conducted a comprehensive analysis of the physicochemical properties, gene structure, chromosomal localization, conserved structural domains and motifs, cis-acting regulatory elements, and evolutionary relationships of these genes. Using transcriptome data, we analyzed the expression patterns of BrHAT family members and predicted interactions between proteins; the results indicated that BrHATs play an important role in the low-temperature response of B. rapa L. HAT inhibitor (curcumin; CUR) and histone deacetylase inhibitor (Trichostatin A; TSA) were applied to four B. rapa L. varieties varying in cold resistance under the same low-temperature conditions, and changes in the physiological indexes of these four varieties were analyzed. The inhibitor treatment attenuated the effect of low temperature on seed germination, and curcumin treatment was most effective, indicating that the germination period was primarily regulated by histone acetylase. Both inhibitor treatments increased the activity of protective enzymes and the content of osmoregulatory substances in plants, suggesting that histone acetylation and deacetylation play a significant role in the response of B. rapa L. to low-temperature stress. The qRT-PCR analyses showed that the expression patterns of BrHATs were altered under different inhibitor treatments and low-temperature stress; meanwhile, we found three significantly differentially expressed genes. In sum, the process of histone acetylation is involved in the cold response and the BrHATs gene plays a role in the cold stress response.

Establishment and characterization of a gill cell line from Takifugu obscurus and transcriptome analysis of its gene expression profiles upon low temperature

Takifugu obscurus is a farmed fish of great economic importance in China. The rapid development of T. obscurus aquaculture industry has been accompanied by disease and low-temperature stress, resulting in huge economic losses. Cell lines are used extensively in teleost physiology and pathology as the most cost-effective platform for in vitro research. A novel gill cell line of T. obscurus (named TOG) was first successfully established, and passed through 52 generations. The optimal conditions for TOG growth were 20 % FBS concentration and 24 °C, TOG could be grown in both hypotonic (150 mOsmol-kg-1) and hypertonic (600 mOsmol-kg-1) environments. TOG was determined to be derived from T. obscurus by sequencing the mitochondrial COI gene. Karyotype analysis revealed that the chromosome number of TOG was 44 (2n = 44). Transfection experiment showed that TOG was able to express foreign genes. Furthermore, several immune-related genes were significantly up-regulated in TOG after LPS and poly (I:C) stimulation, including tlr3, isg15, il1β and il10. Additionally, transcriptome analysis of TOG under low-temperature stress (24 °C, 18 °C, 12 °C, 10 °C and 8 °C) found that differentially expressed genes (DEGs) were significantly clustered in several immunological and energy metabolic pathways, and cold stress could disrupt the immune barrier and reduce immunity by downregulating the immune-related pathways. Additionally, weighted gene co-expression network analysis (WGCNA) revealed that bule module and turquoise module, which were closely correlated with low temperature and the degree of fish damage, were both predominantly found in PPAR, NOD-like receptor and Toll-like receptor signaling pathway. Hub genes were identified in these two modules, including mre11, clpb, dhx15, ddx18 and utp15. TOG cell line will become an effective experimental platform for genetic and immunological research, and our results would help us gain a deeper insight into the molecular mechanism of cold tolerance in teleost.

Transcriptome, histology, and enzyme activities analysis of liver in Phoxinus lagowskii to the low temperature stress and recovery

Assessing the response and resilience of fish to low temperatures over different time scales can provide valuable insights into their mechanisms of adaptation to cold conditions. Farmed Amur minnows (Phoxinus lagowskii) frequently encounter low temperatures, especially during winter. However, the specific responses of P. lagowskii to low-temperature stress remain largely unexplored. In this study, we examined serum glucose and cortisol levels, histological changes, enzymes associated with phosphate and carbohydrate metabolism, triglyceride levels, and liver transcriptomics under various conditions: control (CK), short-term cold exposure (6 days, SC), prolonged cold exposure (14 days, PC), and recovery (RY) from cold exposure at 2 °C. Liver vacuolation was observed during short-term cold exposure. Additionally, we analyzed the enzymatic activity related to carbohydrate and lipid metabolism in serum and liver. Liver transcriptomic data revealed that the PPAR signaling pathway and autophagy-related genes were enriched during short-term cold exposure. Carbohydrate metabolism-related pathways, including the AMPK and MAPK signaling pathways, were significantly enriched after prolonged cold exposure. Metabolic pathways such as fat digestion and absorption, glycine, serine, and threonine metabolism, and arginine and proline metabolism were significantly enriched in the recovery group. Rapid warming after prolonged cold stress allowed P. lagowskii to recover quickly. These findings suggest that P. lagowskii has a strong adaptive capacity for energy metabolism during prolonged cold exposure and the ability to recover rapidly from cold stress. A comprehensive examination of the histological, physiological, biochemical, and molecular responses of P. lagowskii to low temperatures is crucial for developing effective strategies for cultivating this species in challenging environments.

Genome-Wide Identification of the DOF Gene Family in Kiwifruit (Actinidia chinensis) and Functional Validation of AcDOF22 in Response to Drought Stress.

DNA-binding one zinc finger (DOF) transcription factors are crucial plant-specific regulators involved in growth, development, signal transduction, and abiotic stress response generation. However, the genome-wide identification and characterization of AcDOF genes and their regulatory elements in kiwifruit (Actinidia chinensis) has not been thoroughly investigated. In this study, we screened the kiwifruit genome database and identified 42 AcDOF genes (AcDOF1 to AcDOF42). Phylogenetic analysis facilitated the categorization of these genes into five subfamilies (DOF-a, DOF-b, DOF-c, DOF-d, and DOF-e). We further analyzed the motifs, conserved domains, gene structures, and collinearity of the AcDOFgene family. Gene ontology (GO) enrichment analysis indicated significant enrichment in the "flower development" term and the "response to abiotic stress" category. Promoter prediction analysis revealed numerous cis-regulatory elements related to responses to light, hormones, and low-temperature and drought stress in AcDOF promoters. RNA-seq expression profiles demonstrated the tissue-specific expression of AcDOF genes. Quantitative real-time PCR results showed that six selected genes (AcDOF04, AcDOF09, AcDOF11, AcDOF13, AcDOF21, and AcDOF22) were differentially induced by abscisic acid (ABA), methyl jasmonate (MeJA), and cold, salt, and drought stresses, with AcDOF22 specifically expressed at high levels in drought-tolerant cultivars. Further experiments indicated that transient AcDOF22 overexpression in kiwifruit leaf disks reduced water loss and chlorophyll degradation. Additionally, AcDOF22 was localized to the nucleus and exhibited transcriptional activation, enhancing drought resistance by activating the downstream drought marker gene AcDREB2A. These findings lay the foundation for elucidating the molecular mechanisms of drought resistance in kiwifruit and offer new insights into drought-resistant breeding.

EjCBF3 conferred cold-resistance through the enhancement of antioxidase activity in loquat (Eriobotrya japonica Lindl.)

Low-temperature is a serious threat to production of plants, and cold damage of loquat (Eriobotrya japonica Lindl.) reduces fruit yield tremendously. C-Repeat Binding Factors (CBFs) are known to work as core regulators for cold adaption in plants. However, loquat EjCBFs and their mechanism for cold tolerance have not been identified. In this study, 3 EjCBFs were discovered from loquat using genome-wide searching strategy, which were candidates responding to low-temperature stress supported by analysis of conserved domains and cis-elements in promoters. The greatest up-regulation was shown on EjCBF3 both in loquat leaves and young fruits subjected to low-temperature treatment. EjCBF3 was located in the cell nucleus of Nicotiana benthamiana (N. benthamiana), and its transcriptional activation activity was verified in yeast. Transient over-expression of EjCBF3 alleviated chilling injury through the increase of antioxidase peroxidase (POD) and superoxide dismutase (SOD) activity in N. benthamiana, and the removal of H2O2 with the application of scavenger attenuated cold damage in loquat leaves. Higher survival rate and lower electrolyte leakage were found in Arabidopsis thaliana (A. thaliana) treated with low-temperature stress with the over-expression (OE) of EjCBF3. Furthermore, the induction of cold-regulated genes (CORs) including COR15A, COR47, COR78, and KIN1 were greater in OE plants than that of wild type (WT) suffering cold stress. Results provide new insights into the cold tolerance of loquat and a novel cold-resistant gene, EjCBF3, for loquat breeding.

Transcriptome analysis of Sesuvium portulacastrum L. uncovers key genes and pathways involved in root formation in response to low-temperature stress.

Sesuvium portulacastrum L., a perennial facultative halophyte, is extensively distributed across tropical and subtropical coastal regions. Its limited cold tolerance significantly impacts both the productivity and the geographical distribution of this species in higher-latitude areas. In this study, we employed RNA-Seq technology to delineate the transcriptomic alterations in Sesuvium plants exposed to low temperatures, thus advancing our comprehension of the molecular underpinnings of this physiological adaptation and root formation. Our findings demonstrated differential expression of 10,805, 16,389, and 10,503 genes in the low versus moderate temperature (LT vs. MT), moderate versus high temperature (MT vs. HT), and low versus high temperature (LT vs. HT) comparative analyses, respectively. Notably, the gene categories "structural molecule activity", "ribosome biogenesis", and "ribosome" were particularly enriched among the LT vs. HT-specific differentially expressed genes (DEGs). When synthesizing the insights from these three comparative studies, the principal pathways associated with the cold response mechanism were identified as "carbon fixation in photosynthetic organisms", "starch and sucrose metabolism", "plant hormone signal transduction", "glycolysis/gluconeogenesis", and "photosynthesis". In addition, we elucidated the involvement of auxin signaling pathways, adventitious root formation (ARF), lateral root formation (LRF), and novel genes associated with shoot system development in root formation. Subsequently, we constructed a network diagram to investigate the interplay between hormone levels and pivotal genes, thereby clarifying the regulatory pathways of plant root formation under low-temperature stress and isolating key genes instrumental in root development. This study has provided critical insights into the molecular mechanisms that facilitate the adaptation to cold stress and root formation in S. portulacastrum.

Effect of Cold Plasma Treatment on Seed Quality Parameters under Cold Stress in Rice (Oryza sativa L.)

Abiotic stresses impinge rice production all over the world. Low temperature stress is one among the major abiotic stresses in crop plants significantly affecting plant growth, survival, reproduction, and dispersal. Therefore an experiment was carried out on rice variety BPT 5204 to study the effects of cold plasma treatment under cold stress. Attempt was made to standardize appropriate stage of exposure (dry seeds, sprouted seeds), voltage (30kv, 20kv) and duration of exposure (10min, 20min) based on the performance in vigour tests i.e., germination, seedling dry weight, seedling vigour index-II, field emergence test, abnormality and imbibition tests at a temperature of 18°C. Results indicated that exposure of sprouts of BPT 5204 at 20kv for 20min has given highest germination (88%), seedling dry weight (68.10 mg), seedling vigour index II (597), field emergence (77%), imbibition rate (0.495) and lowest abnormality (12%) in comparison to control and other treatments. This indicates that cold plasma treated at 20kv for 20min on paddy sprouts had a greater stimulatory effect on plant growth and development under cold temperature conditions.

Hepatic Metabolomic Responses to Low-Temperature Stress in the Invasive Turtle, Trachemys scripta elegans.

Investigating the physiological and biochemical changes of ectothermic species before entering hibernation would contribute to the understanding of how they adapt to low-temperature environments. Here, red-eared slider turtle (Trachemys scripta elegans) hatchlings were maintained under different thermal treatments (24 °C, slowly decreasing temperatures from 24 °C to 14 °C, and to 4 °C). Hepatic metabolite alterations were measured to assess the metabolic impacts of low-temperature stress in this species. Of these differentially changed metabolites, some (e.g., raffinose, spermidine, allocholic acid, taurohyocholate, 2-ketobutyric acid, acetylcysteine) were shown to decrease, while others (e.g., stearolic acid, D-mannose) increased in low-temperature treatments. Our results indicated that short-term low-temperature stress might have limited impacts on lipid and energy metabolism in this species. The changes in other metabolites (e.g., allocholic acid, taurohyocholate, spermine, acetylcysteine) might be associated with a low food intake (and thus reduced digestive performance) and weakened immune ability of low-temperature-exposed animals.

Target of rapamycin coordinates auxin are involved in exogenous melatonin regulated low temperature tolerance in cucumber seedlings

Low temperature (LT) is an important environmental factor affecting the growth and yield of plants. Melatonin (MT) can effectively enhance the LT tolerance of cucumber. This study found that LT stress induced the expression of Comt1 (caffeic acid O-methyltransferase 1), with the highest expression being about 2-times that of the control. Meanwhile, the content of MT was found to be roughly 63.16% of that in the control samples. Compared with LT treatment alone, exogenous MT pretreatment upregulated the expression levels of TOR (Target of rapamycin), PIN1 (Pin-formed 1), and YUC4 (YUCCA 4), with maximum upregulations reaching approximately 66.67%, 79.32%, and 42.86%, respectively. These results suggest that MT may modulate the tolerance of cucumber seedlings to LT stress by regulating the expression of TOR, PIN1, and YUC4. In addition, co-treatment with AZD-8055 (a TOR inhibitor) or NPA (N-1-naphthylphthalamic acid, an auxin polar transport inhibitor) and MT attenuated MT-induced resistance to LT stress, leading to higher levels of reactive oxygen species (ROS), reduced antioxidant defense capacity, and increased damage to the membrane system in cucumber seedlings. Concurrently, the content of osmoregulatory substances and the photosynthesis decreased. These results demonstrate that both TOR and auxin were required for MT to alleviate LT-induced damage in cucumber. In summary, the present study demonstrates that TOR and auxin signaling synergistically contribute to alleviating LT damage in cucumber seedlings by exogenous MT. These findings help us understand the function of MT and provide insights into the regulatory network of MT that regulates the LT tolerance of plants.

Low temperature exposure influences nitrogen metabolism resulting in decreased Cry1Ac insecticidal endotoxin content in cotton seeds

BackgroundSudden temperature drops, resulting from extreme weather events, often occur during the boll-setting period of cotton in Xinjiang, China, causing decreased expression of Bacillus thuringiensis (Bt) insecticidal proteins in cotton bolls. The precise threshold temperatures and durations that lead to significant changes in Cry1Ac endotoxin levels under low temperatures remain unclear. To address this, we investigated the effects of different temperatures and stress durations on Cry1Ac endotoxin levels in cotton bolls. In 2020–2021, two Bt transgenic cotton varieties, conventional Sikang1 and hybrid Sikang3, were selected as experimental materials. Various low temperatures (ranging from 16 to 20 °C) with different durations (12 h, 24 h and 48 h) were applied during the peak boll-setting period.ResultsAs the temperature decreased, the Cry1Ac endotoxin content in the boll shell, fiber, and seed exhibited a declining trend. Moreover, the threshold temperature which caused a significant reduction in Cry1Ac endotoxin content increased with the prolonged duration of low-temperature stress. Among the components of cotton bolls, seeds were most affected by low-temperature stress, with the threshold temperature for a significant reduction in Cry1Ac endotoxin content ranging from 17 °C to 19 °C. Correlation analysis indicated that low temperatures led to a decrease in protein synthesis capacity and an increase in degradation ability, resulting in reduced Cry1Ac endotoxin content. Pathway analysis revealed that both free amino acid and peptidase had significant negative effects on Cry1Ac endotoxin content.ConclusionIn summary, when the daily average temperature was ≤ 19 °C, implementing cultural practices to reduce free amino acid content and peptidase activity could serve as effective cold defense strategies for Bt cotton production.

Vitamin C as a functional enhancer in the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab, Scylla paramamosain

This experiment was conducted to explore the effects of dietary vitamin C supplementation on non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab (Scylla paramamosain). Mud crabs with an initial weight of 14.67 ± 0.13 g were randomly divided into 6 treatments and fed diets with 0.86 (control), 44.79, 98.45, 133.94, 186.36 and 364.28 mg/kg vitamin C, respectively. The experiment consisted of 6 treatments, each treatment was designed with 4 replicates and each replicate was stocked with 8 crabs. After 42 days of feeding experiment, 2 crabs were randomly selected from each replicate, and a total of 8 crabs in each treatment were carried out 72 h low-temperature challenge experiment. The results showed that crabs fed diets with 186.36 and 364.28 mg/kg vitamin C significantly improved the activities of alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemolymph and hepatopancreas (P < 0.05). Crabs fed diet with 133.94 mg/kg vitamin C significantly decreased the concentration of nitric oxide (NO) and the activity of nitric oxide synthase (NOS) in hemolymph (P < 0.05). Diet with 133.94 mg/kg vitamin C was improved the activity of polyphenol oxidase (PPO) and the concentration of albumin (ALB) in hemolymph. Crabs fed diet with 133.94 mg/kg vitamin C showed lower concentration of malondialdehyde (MDA) in hemolymph and hepatopancreas than those fed the other diets. Meanwhile, crabs fed diet with 98.45 mg/kg vitamin C showed higher activity of total superoxide dismutase (T-SOD) in hemolymph, and crabs fed diet with 133.94 mg/kg vitamin C showed higher activity of T-SOD in hepatopancreas. Crabs fed diet with 186.36 mg/kg vitamin C significantly decreased the concentration of reduced glutathione (GSH) and the activity of glutathione peroxidase (GSH-PX) in hepatopancreas (P < 0.05). In normal temperature, crabs fed diets with 133.94 mg/kg vitamin C significantly up-regulated the expression levels of gpx (glutathione peroxidase) and trx (thioredoxin) in hepatopancreas compared with the control treatment (P < 0.05). The highest expression levels of relish, il16 (interleukin 16), caspase 2 (caspase 2), p38 mapk (p38 mitogen-activated protein kinases) and bax (bcl-2 associated x protein) in hepatopancreas were found at crabs fed control diet (P < 0.05). Moreover, crabs fed diet with 133.94 mg/kg vitamin C showed higher expression levels of alf-3 (anti-lipopolysaccharide factor 3) and bcl-2 (B-cell lymphoma 2) in hepatopancreas than those fed the other diets (P < 0.05). Under low-temperature stress, crabs fed diet with 133.94 mg/kg vitamin C significantly improved the expression levels of hsp90 (heat shock protein 90), cat (catalase), gpx, prx (thioredoxin peroxidase) and trx in hepatopancreas (P < 0.05). In addition, dietary with 133.94 vitamin C significantly up-regulated the expression levels of alf-3 and bcl-2 (P < 0.05). Based on two slope broken-line regression analysis of activity of PPO against the dietary vitamin C level, the optimal dietary vitamin C requirement was estimated to be 144.81 mg/kg for juvenile mud crab. In conclusion, dietary 133.94–144.81 mg/kg vitamin C significantly improved the non-specific immune defense, antioxidant capacity and resistance to low-temperature stress of juvenile mud crab.

Adaptation of Rhizobium leguminosarum sv. trifolii strains to low temperature stress in both free-living stage and during symbiosis with clover

Legume-rhizobial symbiosis plays an important role in agriculture and ecological restoration. This process occurs within special new structures, called nodules, formed mainly on legume roots. Soil bacteria, commonly known as rhizobia, fix atmospheric dinitrogen, converting it into a form that can be assimilated by plants. Various environmental factors, including a low temperature, have an impact on the symbiotic efficiency. Nevertheless, the effect of temperature on the phenotypic and symbiotic traits of rhizobia has not been determined in detail to date. Therefore, in this study, the influence of temperature on different cell surface and symbiotic properties of rhizobia was estimated. In total, 31 Rhizobium leguminosarum sv. trifolii strains isolated from root nodules of red clover plants growing in the subpolar and temperate climate regions, which essentially differ in year and day temperature profiles, were chosen for this analysis. Our results showed that temperature has a significant effect on several surface properties of rhizobial cells, such as hydrophobicity, aggregation, and motility. Low temperature also stimulated EPS synthesis and biofilm formation in R. leguminosarum sv. trifolii. This extracellular polysaccharide is known to play an important protective role against different environmental stresses. The strains produced large amounts of EPS under tested temperature conditions that facilitated adherence of rhizobial cells to different surfaces. The high adaptability of these strains to cold stress was also confirmed during symbiosis. Irrespective of their climatic origin, the strains proved to be highly effective in attachment to legume roots and were efficient microsymbionts of clover plants. However, some diversity in the response to low temperature stress was found among the strains. Among them, M16 and R137 proved to be highly competitive and efficient in nodule occupancy and biomass production; thus, they can be potential yield-enhancing inoculants of legumes.

Effects of Low-Temperature Stress on Physiological Characteristics and Microstructure of Stems and Leaves of Pinus massoniana L.

Pinus massoniana L. is one of the most important conifer species in southern China and is the mainstay of the forest ecosystem and timber production, yet low temperatures limit its growth and geographical distribution. This study used 30-day-old seedlings from families of varying cold-tolerance to examine the morphological traits of needles and stems, chlorophyll fluorescence characteristics, protective enzymes, and changes in starch and lignin under different low-temperature stresses in an artificial climate chamber. The results showed that the seedlings of Pinus massoniana exhibited changes in phenotypic morphology and tissue structure under low-temperature stress. Physiological and biochemical indexes such as protective enzymes, osmoregulatory substances, starch, and lignin responded to low-temperature stress. The cold-tolerant family increased soluble sugars, starch grain, and lignin content as well as peroxidase activity, and decreased malondialdehyde content by increasing the levels of actual photochemical efficiency (ΦPSII), electron transport rate (ETR), and photochemical quenching (qP) to improve the cold tolerance ability. This study provides a reference for the selection and breeding of cold-tolerant genetic resources of Pinus massoniana and the mechanism of cold-tolerance, as well as the analysis of the mechanism of adaptation of Pinus massoniana in different climatic regions of China.

Identification and expression analysis of CCCH gene family and screening of key low temperature stress response gene CbuC3H24 and CbuC3H58 in Catalpa bungei

Catalpa bungei, a tree indigenous to China, is renowned for its superior timber quality and as an ornamental in horticulture. To promote the cultivation of C. bungei in cold regions and expand its distribution, enhancing its cold tolerance is essential. The CCCH gene family is widely involved in plant growth, development, and expression under stress conditions, including low-temperature stress. However, a comprehensive identification and analysis of these genes have not yet been conducted. This study aims to identify key cold-tolerance-related genes within the CCCH gene family of C. bungei, providing the necessary theoretical support for its expansion in cold regions. In this study, 61 CCCH genes within C. bungei were identified and characterized. Phylogenetic assessment divided these genes into 9 subfamilies, with 55 members mapped across 16 chromosomes. The analysis of gene structures and protein motifs indicated that members within the same subfamily shared similar exon/intron distribution and motif patterns, supporting the phylogenetic classification. Collinearity analysis suggested that segmental duplications have played a significant role in the expansion of the C. bungei CCCH gene family. Notably, RNA sequencing analysis under 4 °C cold stress conditions identified CbuC3H24 and CbuC3H58 as exhibiting the most significant responses, highlighting their importance within the CCCH zinc finger family in response to cold stress. The findings of this study lay a theoretical foundation for further exploring the mechanisms of cold tolerance in C. bungei, providing crucial insights for its cultivation in cold regions.

Transcriptome analysis of the common moss Bryum pseudotriquetrum grown under Antarctic field condition.

Mosses are distributed all over the world including Antarctica. Although Antarctic mosses show active growth in a short summer season under harsh environments such as low temperature, drought and high levels of UV radiation, survival mechanisms for such multiple environmental stresses of Antarctic mosses have not yet been clarified. In the present study, transcriptome analyses were performed using one of the common mosses Bryum pseudotriquetrum grown under an Antarctic field and artificial cultivation conditions. Totally 88205 contigs were generated by de novo assembly, among which 1377 and 435 genes were significantly up and downregulated, respectively, under Antarctic field conditions compared with artificial cultivation conditions at 15°C. Among the upregulated genes, a number of lipid metabolism-related and oil body formation-related genes were identified. Expression levels of these genes were increased by artificial environmental stress treatments such as low temperature, salt and osmic stress treatments. Consistent with these results, B. pseudotriquetrum grown under Antarctic field conditions contained large amounts of fatty acids, especially α-linolenic acid, linolenic acid and arachidonic acid. In addition, proportion of unsaturated fatty acids, which enhance membrane fluidity, to the total fatty acids was also higher in B. pseudotriquetrum grown under Antarctic field conditions. Since lipid accumulation and unsaturation of fatty acids are generally important factors for the acquisition of various environmental stress tolerance in plants, these intracellular physiological and metabolic changes may be responsible for the survival of B. pseudotriquetrum under Antarctic harsh environments.

Comprehensive Evaluation of 65 Leafy Mustard Cultivars for Chilling Tolerance to Low Temperature Stress at the Seedling Stage

Comprehensive Evaluation of 65 Leafy Mustard Cultivars for Chilling Tolerance to Low Temperature Stress at the Seedling Stage