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Background Rice plants show yellowing, stunting, withering, reduced tillering and utimately low productivity in susceptible varieties under low temperature stress. Comparative transcriptome analysis was performed to identify novel transcripts, gain new insights into different gene expression and pathways involved in cold tolerance in rice. Results Comparative transcriptome analyses of 5 treatments based on chilling stress exposure revealed more down regulated genes in susceptible and higher up regulated genes in tolerant genotypes. A total of 13930 and 10599 differentially expressed genes (DEGs) were detected in cold susceptible variety (CSV) and cold tolerant variety (CTV), respectively. A continuous increase in DEGs at 6, 12, 24 and 48 h exposure of cold stress was detected in both the genotypes. Gene ontology (GO) analysis revealed 18 CSV and 28 CTV term significantly involved in molecular function, cellular component and biological process. GO classification showed a significant role of transcription regulation, oxygen, lipid binding, catalytic and hydrolase activity for tolerance response. Absence of photosynthesis related genes, storage products like starch and synthesis of other classes of molecules like fatty acids and terpenes during the stress were noticed in susceptible genotype. However, biological regulations, generation of precursor metabolites, signal transduction, photosynthesis, regulation of cellular process, energy and carbohydrate metabolism were seen in tolerant genotype during the stress. KEGG pathway annotation revealed more number of genes regulating different pathways resulting in more tolerant. During early response phase, 24 and 11 DEGs were enriched in CTV and CSV, respectively in energy metabolism pathways. Among the 1583 DEG transcription factors (TF) genes, 69 WRKY, 46 bZIP, 41 NAC, 40 ERF, 31/14 MYB/MYB-related, 22 bHLH, 17 Nin-like 7 HSF and 4C3H were involved during early response phase. Late response phase showed 30 bHLH, 65 NAC, 30 ERF, 26/20 MYB/MYB-related, 11 C3H, 12 HSF, 86 Nin-like, 41 AP2/ERF, 55 bZIP and 98 WRKY members TF genes. The recovery phase included 18 bHLH, 50 NAC, 31 ERF, 24/13 MYB/MYB-related, 4 C3H, 4 HSF, 14 Nin-like, 31 bZIP and 114 WRKY TF genes. Conclusions Transcriptome analysis of contrasting genotypes for cold tolerance detected the genes, pathways and transcription factors involved in the stress tolerance.

Background The basic helix-loop-helix (bHLH) transcription factors play important roles in many processes in plant growth, metabolism and responses to abiotic stresses. Although, the sequence of Chinese white pear genome (cv. ‘Dangshansuli’) has already been reported, there is still a lack of clarity regarding the bHLH family genes and their evolutionary history. Results In this work, a genome-wide identification of the bHLH genes in Chinese white pear was performed, and we characterized the functional roles of these PbrbHLH genes in response to abiotic stresses. Based on the phylogenetic analysis and structural characteristics, 197 identified bHLH genes could be well classified into 21 groups. Expansion of PbrbHLH gene family was mainly driven by WGD and dispersed duplication with the purifying selection from the recent WGD. The functional annotation enrichment showed that the majority of PbrbHLHs were enriched in the GO terms and KEGG pathways involved in responds to stress conditions as TFs. Transcriptomic profiles and qRT-PCR revealed that PbrbHLH7 , PbrbHLH8 , PbrbHLH128 , PbrbHLH160 , PbrbHLH161 and PbrbHLH195 were significantly up-regulated under cold and drought treatments. In addition, PbrbHLH195 -silenced pear seedlings display significant reduced cold tolerance, exhibiting reduced chlorophyll content, as well as increased electrolyte leakage and concentrations of malondialdehyde and H 2 O 2 . Conclusion For the first time, a comprehensive analysis identified the bHLH genes in Chinese white pear and demonstrated that PbrbHLH195 is involved in the production of ROS in response to cold stress, suggesting that members of the PbrbHLH family play an essential role in the stress tolerance of pear.

CsbHLH18, a bHLH transcription factor of Citrus sinensis, functions as a positive regulator of cold tolerance due to promoted ROS scavenging, and directly targets a POD gene. Abstract The basic helix–loop–helix (bHLH) transcription factors (TFs) comprise one of the largest gene families in plants, and participate in various physiological processes, but the physiological role and regulatory function of the majority of bHLHs remain poorly understood. Here, a total of 56 putative CsbHLH genes were identified in sweet orange (Citrus sinensis) based on a genome-wide analysis. The CsbHLH genes, except four members, were distributed throughout nine chromosomes and divided into 19 subgroups. Most of the CsbHLH genes were responsive to cold stress, with the greatest up-regulation being observed in CsbHLH18. CsbHLH18 is localized in the nuclei and has transcriptional activation activity. Overexpression of CsbHLH18 conferred enhanced cold tolerance in transgenic tobacco. The transgenic plants accumulated significantly less reactive oxygen species (ROS), concurrent with increased activities and transcript levels of antioxidant enzymes. In contrast, knockdown of bHLH18 by RNAi in trifoliate orange promoted cold susceptibility, accompanied by down-regulation of antioxidant genes and accumulation of more ROS. Protein–DNA interaction assays demonstrate that CsbHLH18 directly and specifically binds to and activates the promoter of CsPOD. Taken together, these findings indicate that CsbHLH18 plays a positive role in cold tolerance through, at least partly, modulation of ROS homeostasis by directly regulating the antioxidant gene.

Background Grape production in continental climatic regions suffers from the combination of drought and cold stresses during winter. Developing a reliable system to simulate combined drought–cold stress and to determine physiological responses and regulatory mechanisms is important. Evaluating tolerance to combined stress at germplasm level is crucial to select parents for breeding grapevines. Results In the present study, two species, namely, Vitis amurensis and V. vinifera cv. ‘Muscat Hamburg’, were used to develop a reliable system for evaluating their tolerance to drought–cold stress. This system used tissue −cultured grapevine plants, 6% PEG solution, and gradient cooling mode to simulate drought–cold stress. V. amurensis had a significantly lower LT50 value (the temperature of 50% electrolyte leakage) than ‘Muscat Hamburg’ during simulated drought–cold stress. Thus, the former had higher tolerance than the latter to drought–cold stress based on electrolyte leakage (EL) measurements. Moreover, the chlorophyll fluorescence responses of V. amurensis and ‘Muscat Hamburg’ were also analyzed under drought–cold stress. The maximum photochemical quantum yield of PS II ( Fv/Fm ) exhibited a significant linear correlationship with EL. The relationship of EL with Fv/Fm in the other four genotypes of grapevines under drought–cold stress was also detected. Conclusions A novel LT50 estimation model was established, and the LT50 values can be well calculated based on Fv/Fm in replacement of EL measurement. The Fv/Fm –based model exhibits good reliability for evaluating the tolerance of different grapevine genotypes to drought–cold stress.

Fenugreek (Trigonella foenum-graecum L.) is one of the oldest cultivated plants grown for its leaves and seeds that are used for both culinary and medicinal purpose. This study aims to evaluate the effect of ethanol concentration (30, 50, 70 and 96% (v/v) of ethanol in water) as a solvent for the extraction of total phenolic content (TPC) and antioxidant properties (antiradical activity (ARA), transition metal reducing power (TMRP), iron chelating ability (ICA)) of seed extracts of spring variety Ovari 4 (FSV) and winter variety PSZ.G.SZ (FWV) fenugreek, and separate and identify the major phenolics of the extracts by HPLC-ESI-MS. The results indicated that 70% ethanol solution resulted in the maximum amount of TPC for both FSV and FWV seeds. The TPC decreased in the treatments in the following order: 70% ethanol > 96% ethanol > 50% ethanol > 30% ethanol, whereas extraction yield changed in a different manner: 30% ethanol > 50% ethanol > 70% ethanol > 96% ethanol. The extracts from seeds of both fenugreek varieties obtained with 70% and 96% ethanol showed equal high RSA while superior TMRP and ICA were observed in 70% ethanol extracts. The TMRP and ICA were strongly correlated with TPC for both varieties. The correlation between RSA and TPC was high, but not significant. Thus, the obtained data indicate the 70% ethanol solvent suitability for efficient extraction of phenolic compounds from seeds of the FWV and FSV. According to an HPLC-ESI-MS analysis, the polyphenolic profiles of fenugreek are presumably formed by flavone C-glycosides with apigenin or luteolin as aglycone linked with different glycones. High antioxidant activity of FWV seeds can be an adaptation to cold stress of the winter variety aimed at strengthening the antioxidant defense of the germinating seeds.

The popular leafy vegetable lettuce ( Lactuca sativa L.) is susceptible to cold stress during the growing season, which slows growth rate, causes leaf yellowing and necrosis, and reduced yield and quality. In this study, transcriptomic and metabolomic analyses of two cold-resistant lettuce cultivars (GWAS-W42 and F11) and two cold-sensitive lettuce cultivars (S13K079 and S15K058) were performed to identify the mechanisms involved in the cold response of lettuce. Overall, transcriptome analysis identified 605 differentially expressed genes (DEGs), including significant enrichment of genes involved in the flavonoid and flavonol ( CHS , CHI , F3H , FLS , CYP75B1 , HCT , etc.) biosynthetic pathways related to oxidation–reduction and catalytic activity. Untargeted metabolomic analysis identified fifteen flavonoid metabolites and 28 other metabolites potentially involved in the response to cold stress; genistein, quercitrin, quercetin derivatives, kaempferol derivatives, luteolin derivatives, apigenin and their derivatives accumulate at higher levels in cold-resistant cultivars. Moreover, MYBs, bHLHs, WRKYs and Dofs also play positive role in the low temperature response, which affected the expression of structural genes contributing to the variation of metabolites between the resistant and sensitive. These results provide valuable evidence that the metabolites and genes involved in the flavonoid biosynthetic pathway play important roles in the response of lettuce to cold stress.

Temperature is an important limiting factor in the counter-seasonal cultivation of pepper. Currently, there are no studies on transcriptomic analysis of ‘cold stress memory’ in pepper. In this study, in order to understand the mechanism of ‘cold stress memory’ in pepper ( Capsicum annuum L.), seedlings were subjected to the following treatments: normal temperature treatment (P0), the first cold treatment for 3 days (P3), the recovery temperature treatment for 3 days (R3), and another cold treatment for 3 days (RP3). The results showed that P3 plants wilted the most, RP3 the second and R3 the least. Leaf reactive oxygen species (ROS) and electrolyte leakage were the most in P3, the second in RP3 and the least in R3. In addition, RP3 had the highest accumulation of zeaxanthin, violaxanthin and β-cryptoxanthin, followed by P3, and R3 had the least. These results suggest that pepper seedlings are characterized by ‘cold stress memory’. Transcriptomics was used to analyze the key genes and transcription factors involved in the biosynthesis of zeaxanthin, violaxanthin and β-cryptoxanthin during the formation of ‘cold stress memory’. This study provides candidate genes and transcription factors for an in-depth study of the cold tolerance mechanism in pepper.

Winter cold wave adaptation strategies in hot climates due to climate change didn’t receive the deserved attention from previous studies. Therefore, this study comprehensively investigates the impact of various windbreak parameters on mitigating winter cold stress in hot steppe-arid climate. A microclimate model for a residential campus was built and validated through on-site measurement on a typical winter day to assess thirty-two scenarios for tree characteristics and spatial configuration windbreak parameters based on PET, wind speed, and Air Temperature (AT). Moreover, four configurations, that had best results on mitigating cold stress in winter, were tested during typical summer conditions to couple the assessment of cold and hot seasons. Additionally, environmental analysis for all scenarios was conducted. The results revealed that the most effective parameters for mitigating cold stress are tree distribution, Leaf Area Density (LAD), row number, spacing, and shape. Double rows of high LAD and medium height trees with small spacing yielded the best cold stress mitigation effect. Furthermore, the windbreak reduced the cold stress in the morning and night by 19.31% and 18.06%, respectively. It reduced AT and wind speed at night by 0.79 °C and 2.56 m/s, respectively. During summer, very hot PET area was reduced by 21.79% and 19.5% at 12:00 and 15:00, respectively.

Cotton is a vital resource for the textile industry, but cold stress causes serious problems for it during germination and the early phases of seedling development. Both physiological and molecular strategies cotton employ to withstand cold stress are examined in this article. The antioxidant-mediated defense system, which uses both antioxidants that are enzymatic and those that are not to preserve cellular homeostasis, is one of the important areas. The study delves into the interplay between antioxidant defense systems and membrane integrity, as well as the function of cold-responsive molecules in stressful adaption. The review emphasizes the role that suitable solute, including sugars, and osmoprotectants play in improving cold tolerance. We discuss cold-induced hormonal regulation, focusing on ethylene, and the signaling functions of reactive oxygen species (ROS) in triggering protective responses. Additionally, the synthesis of secondary metabolites like terpenoids and flavonoids as defense mechanisms under cold stress is highlighted. At the molecular level, we explore changes in gene expression and the role of microRNAs in growth regulation, alongside abscisic acid (ABA) in cold stress responses. Adaptation strategies, such as priming and acclimation, are reviewed, emphasizing gene expression changes and metabolic pathways during acclimation. In conclusion, we address methods to improve cotton's resistance to cold, such as biotechnological treatments, selection using markers for tolerance to cold genes, and breeding techniques. Additionally taken into consideration is the use of transcriptomic and proteomics analysis to pinpoint targets for enhancing cold tolerance. Through improved breeding and biotechnology techniques, cotton’s resistance to cold stress may be increased, as this thorough investigation reveals.

This study aimed to evaluate the effects of a long-term cold environment on growth performance, physiological behavior, biochemical blood indexes, and hormone levels in Simmental cattle. Thirty Simmental crossbred bulls (weight = 350 ± 17 kg, 13–14 months old) were selected for two trials at autumn suitable temperatures (A-ST) and winter cold temperatures (W-CT) (15 cattle per season). The results showed that compared with the A-ST group, dry matter intake (p < 0.05) and feed:gain (p < 0.01) of the W-CT group increased, while body weight (p < 0.01) and average daily gain (p < 0.01) significantly decreased. Long-term cold stress also increased lying time (p < 0.01), feeding time (p < 0.05), and pulse rate (p < 0.01) in the W-CT group, while the rumen volatile fatty acids content (p < 0.01) and apparent digestibility of nutrients (p < 0.05) were significantly decreased. In terms of blood indicators, long-term cold stress increased the concentrations of glucose, glucose metabolic enzymes, glucocorticoids, triiodothyronine, and tetraiodothyronine in the plasma of the W-CT group (p < 0.05), but the levels of triglycerides, β-hydroxybutyrate, propionate, insulin, and growth hormone were decreased (p < 0.01). In summary, long-term cold stress may inhibit the digestive function of Simmental cattle and enhance the body’s energy metabolism and stress hormone imbalance, ultimately damaging the normal growth and development of the body.