Cold Response Mechanisms Research Articles

Integrative analysis of transcriptome and metabolome provides insights into the underlying mechanism of cold stress response and recovery in two tobacco cultivars

Low temperature is one of major environmental factors limiting the growth, quality and yield of tobacco. However, the molecular mechanism of tobacco cold response remains largely unknown. Here, integrated biochemical, transcriptomic and metabolomic analyses were carried out on tobacco leaves of cold-tolerant cultivar Xiangyan7 and cold-sensitive cultivar Taiyan8 under short- /long-term cold stress and recovery. Physiological and biochemical results showed that Taiyan8 was sensitive while Xiangyan7 was insensitive to cold stress. Integrated transcriptomics and metabolomics analysis revealed several key pathways in tobacco response to cold, including flavonoid biosynthesis, glutathione metabolism, zeatin biosynthesis, phenylpropanoid biosynthesis, starch and sucrose metabolism; two important pathways in the recovery, namely glyoxylate and dicarboxylate metabolism, flavonoid biosynthesis. The two cultivars had similar mechanisms in response to long-term cold stress. Whereas, more enriched pathways were identified in Taiyan8 under short-term stress, and the specifically enriched pathways were mainly involved in amino acid metabolism. By analyzing the metabolites involved in these pathways, a total of 26 key metabolites were screened out. These metabolites contents and biochemical indicator values were used as trait data for correlation analysis with gene expression modules, and 5 highly correlated modules were found. Within these modules, we identified 12 key candidate genes weighted as module hub genes, which involved ATPases, chlorophyll A-B binding protein, S-adenosine methionine decarboxylase, chalcone and stilbene synthases, UDP-glucosyltransferases, alcohol dehydrogenase, abhydrolase, proteins with ankyrin-repeat domains. The expression profiles of these genes further verified their involvement in tobacco cold response and recovery. These findings provide new insights into the regulatory networks of tobacco response to cold stress. • Compared with Taiyan8, Xiangyan7 is relatively insensitive to low temperature stress. • There are some similar mechanisms in the two cultivars response to long-term cold stress. • Amino acid metabolism is specifically enriched in Taiyan8 under short-term cold stress. • Five correlated modules are identified through module-trait relationship analysis. • Twelve key candidate genes are expression validated and discussed.

Comparative Transcriptome Analysis Revealing the Potential Mechanism of Low-Temperature Stress in Machilus microcarpa.

Machilus microcarpa is a rare national tree species in China and possesses important ornamental and ecological value. M. microcarpa can be planted in low-temperature areas, depending on whether its seedlings can withstand the harm. To face this problem, the annual seedlings of M. microcarpa were subjected to five temperature treatments, and eight physiological indicators were measured. Furthermore, comparative transcriptome analysis was performed between M. microcarpa leaves treated at 25°C and −2.8°C. A total of 9,385 differentially expressed genes (DEGs) were involved in low-temperature stress in M. microcarpa. An upregulated (cobA) and five downregulated (HEM, CHLM, CRD, CLH, and PORA) genes associated with the porphyrin and chlorophyll metabolism pathway may reduce chlorophyll synthesis under low-temperature stress. Upregulation of six DEGs (two GAPDHs, PFK, PGAM, PDC, and PK) involved in the glycolysis/gluconeogenesis pathway provided energy for M. microcarpa under adverse cold conditions. Thirteen upregulated and seven downregulated genes related to antioxidant enzymes were also observed under low-temperature stress. Candidate transcription factors (TFs) played key roles in signal transduction under low-temperature stress in M. microcarpa, and quantitative real-time PCR (qRT-PCR) analysis validated the RNA-seq data. The results provide valuable information for further studies on the cold response mechanisms for low-temperature stress in M. microcarpa.

Impact of Cold Stress on Leaf Structure, Photosynthesis, and Metabolites in Camellia weiningensis and C. oleifera Seedlings

Camellia weiningensis Y. K. Li. sp. nov. (CW) is an endemic oil-tea species in Guizhou province, distributed in the alpine karst area, which exhibits cold resistance and better economic characters than C. oleifera (CO). The mechanism of cold response in CW seedlings has not been studied in depth. Herein, we performed anatomical, physiological, and metabolic analyses to assess the impact of cold stress on leaf structure, photosynthesis, and metabolites in CW and CO seedlings. Anatomical analysis of leaves showed CW seedlings had greater leaf and palisade thicknesses, tissue structure tightness, and palisade-spongy tissue ratio to enhance chilling stress (4 °C) tolerance, but freezing stress (−4 °C) caused loosening of the leaf tissue structure in both CW and CO seedlings. Photosynthetic analysis showed a reduction in the chlorophyll (Chl) fluorescence (Fv/Fm) and photosynthetic parameters under freezing stress in both CW and CO seedlings. Cold stress increased the abscisic acid (ABA) contents in both the Camellia species, and CW exhibited the highest ABA content under −4 °C treatment. Additionally, the indole-3-acetic acid (IAA) content was also increased in CW in response to cold stress. An obviously distinct metabolite composition was observed for CW and CO under different temperatures, and significantly changed metabolites (SCMs) were enriched under freezing stress. Prenol lipids, organooxygen compounds, and fatty acyls were the main metabolites in the two Camellia species in response to cold stress. The top key SCMs, such as medicoside G, cynarasaponin F, yuccoside C, and methionyl-proline were downregulated under freezing stress in both CW and CO. The contents of some key metabolites associated with sugar metabolism, such as UDP-glucose, UDP-D-apiose, and fructose 6-phosphate, were higher in CW than in CO, which may contribute to enhancing the cold resistance in CW. Our findings are helpful in explaining how CW adapt to alpine karst cold environments, and will provide a reference for cold tolerance improvement and application of stress-resistant breeding of Camellia in alpine and cold areas.

Genome-wide identification of LEA gene family and cold response mechanism of BcLEA4-7 and BcLEA4-18 in non-heading Chinese cabbage [Brassica campestris (syn. Brassica rapa) ssp. chinensis

Cold stress is a key factor limiting the yield and quality of non-heading Chinese cabbage. The hydrophilic protective protein LEA plays an important role in plant abiotic stress. In this study, 72 BcLEAs were identified from non-heading Chinese cabbage and divided into 9 subfamilies by phylogenetic analysis. Gene structure analysis showed that BcLEAs were unevenly distributed on 10 chromosomes, with few introns. Through analyzing the expression of these genes under cold stress by RNA-seq and qRT-PCR, two genes (BcLEA4–7 and BcLEA4–18) highly sensitive to cold stress were identified, whose roles in cold tolerance of non-heading Chinese cabbage were demonstrated by virus-induced gene silencing. The BcLEA promoters were analyzed to study the cold response mechanism of BcLEA4–7 and BcLEA4–18, revealing that both BcLEA4–7 and BcLEA4–18 promoters contained two CRT/DRE elements. Subsequently, it was found that the promoters isolated from non-heading Chinese cabbage could be activated at low temperatures. Further analysis showed BcCBF2 in non-heading Chinese cabbage interacted with two CRT/DRE elements in BcLEA4–7 and BcLEA4–18 promoters to stimulate their activity, indicating that BcCBF2 is an upstream regulator. Meanwhile, the CRT/DRE element located in BcLEA4–7 promoter (−219 bp to −171 bp) and BcLEA4–18 promoter (−234 bp to −186 bp) was more likely to be activated by BcCBF2, which may be attributed to its flanking sequence. These data laid a foundation for further understanding the functional role and regulatory mechanism of BcLEAs in cold stress tolerance.

Physiological attributes and transcriptomics analyses reveal the mechanism response of Helictotrichon virescens to low temperature stress

BackgroundHelictotrichon virescens is a perennial grass that is primarily distributed in high altitude areas of 2000 ~ 4500 m. It is widely cultivated in the Qinghai-Tibet Plateau of China, strongly resistant to cold, and an essential part of the wild herbs in this region. However, the molecular mechanism of the response of H. virescens to low temperature stress and the key regulatory genes for specific biological processes are poorly understood.ResultsPhysiological and transcriptome analyses were used to study the cold stress response mechanism in H virescens. During the low temperature stress period, the content of chlorophyll a and b decreased more and more with the delay of the treatment time. Among them, the difference between the controls was not significant, and the difference between the control and the treatment was significant. At the same time, the expression of related differential genes was up-regulated during low temperature treatment. In addition, the plant circadian pathway is crucial for their response to cold stress. The expression of differentially expressed genes that encode LHY and HY5 were strongly up-regulated during cold stress.ConclusionsThis study should help to fully understand how H. virescens responds to low temperatures. It answers pertinent questions in the response of perennial herbs to cold stress, i.e., how light and low temperature signals integrate to regulate plant circadian rhythms and Decrease of content of chlorophylls (which can be also accompanied with decrease of total quantity of reaction centers) leads to an increase in photosynthetic damage.

Phosphoproteomics of cold stress-responsive mechanisms in Rhododendron chrysanthum.

As an alpine plant, Rhododendron chrysanthum (R. chrysanthum) has evolved cold resistance mechanisms and become a valuable plant resource with the responsive mechanism of cold stress. We adopt the phosphoproteomic and proteomic analysis combining with physiological measurement to illustrate the responsive mechanism of R. chrysanthum seedling under cold (4°C) stress. After chilling for 12h, 350 significantly changed proteins and 274 significantly changed phosphoproteins were detected. Clusters of Orthologous Groups (COG) analysis showed that significantly changed phosphoproteins and proteins indicated cold changed energy production and conversion and signal transduction. The results indicated photosynthesis was inhibited under cold stress, but cold induced calcium-mediated signaling,reactive oxygen species (ROS) homeostasis and other transcription regulation factors could protect plants from the destruction caused by cold stress. These data provide the insight to the cold stress response and defense mechanisms of R. chrysanthum leaves at the phosphoproteome level.

Low Temperature Antioxidant Activity QTL Associate with Genomic Regions Involved in Physiological Cold Stress Tolerance Responses in Rice (Oryza sativa L.).

Boosting cold stress tolerance in crop plants can minimize stress-mediated yield losses. Asian rice (Oryza sativa L.), one of the most consumed cereal crops, originated from subtropical regions and is generally sensitive to low temperature environments. Within the two subspecies of rice, JAPONICA, and INDICA, the cold tolerance potential of its accessions is highly variable and depends on their genetic background. Yet, cold stress tolerance response mechanisms are complex and not well understood. This study utilized 370 accessions from the Rice Diversity Panel 1 (RDP1) to investigate and correlate four cold stress tolerance response phenotypes: membrane damage, seedling survivability, and catalase and anthocyanin antioxidative activity. Most JAPONICA accessions, and admixed accessions within JAPONICA, had lower membrane damage, higher antioxidative activity, and overall, higher seedling survivability compared to INDICA accessions. Genome-wide association study (GWAS) mapping was done using the four traits to find novel quantitative trait loci (QTL), and to validate and fine-map previously identified QTL. A total of 20 QTL associated to two or more traits were uncovered by our study. Gene Ontology (GO) term enrichment analyses satisfying four layers of filtering retrieved three potential pathways: signal transduction, maintenance of plasma membrane and cell wall integrity, and nucleic acids metabolism as general mechanisms of cold stress tolerance responses involving antioxidant activity.

Convergence and Divergence: Signal Perception and Transduction Mechanisms of Cold Stress in Arabidopsis and Rice.

Cold stress, including freezing stress and chilling stress, is one of the major environmental factors that limit the growth and productivity of plants. As a temperate dicot model plant species, Arabidopsis develops a capability to freezing tolerance through cold acclimation. The past decades have witnessed a deep understanding of mechanisms underlying cold stress signal perception, transduction, and freezing tolerance in Arabidopsis. In contrast, a monocot cereal model plant species derived from tropical and subtropical origins, rice, is very sensitive to chilling stress and has evolved a different mechanism for chilling stress signaling and response. In this review, the authors summarized the recent progress in our understanding of cold stress response mechanisms, highlighted the convergent and divergent mechanisms between Arabidopsis and rice plasma membrane cold stress perceptions, calcium signaling, phospholipid signaling, MAPK cascade signaling, ROS signaling, and ICE-CBF regulatory network, as well as light-regulated signal transduction system. Genetic engineering approaches of developing freezing tolerant Arabidopsis and chilling tolerant rice were also reviewed. Finally, the future perspective of cold stress signaling and tolerance in rice was proposed.

CspB and CspC are induced upon cold shock in Bacillus cereus strain D2.

Bacillus cereus D2, a psychrotrophic strain, plays an essential role in the restoration of heavy metal-contaminated soils, especially at low temperatures. However, the cold shock response mechanisms of this strain are unclear. In this study, the cold shock response of B.cereus D2 was characterized; as per the Arrhenius curve, 10°C was chosen as the cold shock temperature. Six cold shock-like proteins were found and temporarily named cold shock protein (Csp)1-6; the respective genes were cloned and identified. Quantitative real-time PCR results showed that csp1, csp2, csp3, and csp6 were overexpressed under cold shock conditions. Interestingly, after cloning the respective encoding genes into the pET-28a (+) vector and their subsequent transformation into E.coli BL21 (DE3), the strains expressing Csp2 and Csp6 grew faster at 10°C, showing a large number of bacteria. These results suggest that Csp2 and Csp6 are the major cold shock proteins in B.cereus D2. Of note, the comparison of amino acid sequences and structures showed that Csp2 and Csp6 belong to the CspB and CspC families, respectively. Additionally, we show that the number of hydrophobic residues is not a determining feature of major Csps, while, on the other hand, the formation of an α-helix in the context of a leucine residue is the most dominant difference between major and other Bacillus and E.coli Csps.

Comparative physiology and transcriptome response patterns in cold-tolerant and cold-sensitive varieties of Zanthoxylum bungeanum Maxim

Zanthoxylum bungeanum is an economically important tree species of edible, medicinal, and ornamental value. The trees grow in varied climates from tropical to subtropical regions owing to their high resistance to adverse environment. The unstable environmental temperature is one of the important factors affecting the yield and quality of Z. bungeanum. To investigate complex responses to cold stress in Z. bungeanum, we compared cold-tolerant “Fuguhuajiao” (FG) and cold-sensitive “Fengxiandahongpao” (FX) varieties. Physiological measurements and transcriptome sequencing were performed using plant leaves collected at six different timepoints (0, 1, 3, 6, 12, and 24 h) of 4 °C treatment. Chemometrics analysis showed that the physiological cold response in FX at late stage was similar to that in FG at early stage. Based on orthogonal partial least squares discriminant analysis (OPLS-DA), the variable important in projection (VIP) values of peroxidase (POD) and soluble protein were 1.11 and 1.41, which were identified as important physiological indices in the two varieties. Under low temperature stress, there were 3513 differentially expressed genes in FG and 25,157 in FX. Weighted gene co-expression network analysis (WGCNA) revealed that many cold-response genes and pathways were enriched in the MEfirebrick4 module which had a high correlation with POD. Hub genes identified in this module indicated that Z. bungeanum can respond and adapt to cold stress by altering signal transduction, plant hormones, transcription factors, protein modification, functional proteins, metabolism, cell structure, light response, and the circadian clock. Endocytosis-related gene ERD7, abscisic acid pathway-related gene PP2C, late embryogenesis abundant gene LEA D-29, and two plasma membrane/lipid raft-associated remorin genes ZB01477 and pp34 are located at the core of the network, and all play pivotal roles in cold responses. These results of this study highlight cold response mechanisms at the physiological and molecular levels in Z. bungeanum and will contribute to a better understanding of low temperature resistance in related plants.

Transcriptome profiling reveals candidate genes associated with cold stress in mulberry

Low temperatures limit crop growth, yield, and quality in cold areas, and cold tolerance is the only strategy for plants to survive in those areas. However, mulberry’s (Morus alba L.) molecular regulatory mechanisms in response to cold remain poorly understood. In this report, four cDNA libraries were built from two groups, the cold-treated group and the control group, and evaluated by RNA-Seq analysis. A total of 3593 differential expression genes (DEGs) were identified from 20,279 unigenes. Among these, 2337 up-regulated and 1256 down-regulated DEGs were identified under this standard (corrected p value 0.0). Most of these DEGs are involved in plant hormone signal transduction, MAPK signaling pathway, ubiquinone, and other terpenoid-quinone biosynthesis, nitrogen metabolism, and biosynthesis of secondary metabolites. A series of candidate genes related to cold stress were screened out and discussed based on these results. Furthermore, the expression changes of 8 genes under cold stress from RNA-Seq analysis were further validated by real-time quantitative polymerase chain reaction. This research reflects Morus alba L. transcriptome data and may help elucidate the cold response mechanisms of mulberry trees and would be useful in breeding cold-tolerant mulberry plants.

Transcriptome Profiling of Gold Queen Hami Melons under Cold Stress

Hami melon (Cucumis melo L. var. inodorus Jacq) is an important horticultural crop but susceptible to chilling injury during low temperature storage. To characterize the gene expression profiles of Gold Queen Hami melon under the cold stress and discover the key cold stress-induced genes, five cDNA libraries, C0 (control), C12 (control for 12 d), C24 (control for 24 d), L12 (cold treatment at 0.5°C for 12 d) and L24 (cold treatment at 0.5°C for 24 d), were constructed for RNA sequencing (RNA-Seq) and gene expression profiling. A total of 6479 and 7914 differentially expressed genes (DEGs) in L12 and L24 compared with C0 were respectively detected. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses identified the relevant biological functions and metabolic pathways of these differentially expressed genes. In addition, a diverse range of cold response candidate genes were mainly obtained from starch and sucrose metabolism, pentose phosphate pathway and glycolysis/gluconeogenesis, such as genes encoding sucrose-phosphate synthase, α-amylase, β-amylase, sucrose synthase and glucose-6-phosphate dehydrogenase. Various transcription factors with divergent expression patterns were identified. Finally, quantitative real time polymerase chain reaction (qRT-PCR) was conducted to validate the RNA-Seq and gene differentially expression results. This study provides valuable information for further studies on cold response mechanisms and genetic improvement of cold tolerance in Gold Queen Hami melons.

Integrated RNA-Seq Analysis and Meta-QTLs Mapping Provide Insights into Cold Stress Response in Rice Seedling Roots.

Rice (Oryza sativa L.) is a widely cultivated food crop around the world, especially in Asia. However, rice seedlings often suffer from cold stress, which affects their growth and yield. Here, RNA-seq analysis and Meta-QTLs mapping were performed to understand the molecular mechanisms underlying cold tolerance in the roots of 14-day-old seedlings of rice (RPY geng, cold-tolerant genotype). A total of 4779 of the differentially expressed genes (DEGs) were identified, including 2457 up-regulated and 2322 down-regulated DEGs. The GO, COG, KEEG, and Mapman enrichment results of DEGs revealed that DEGs are mainly involved in carbohydrate transport and metabolism, signal transduction mechanisms (plant hormone signal transduction), biosynthesis, transport and catabolism of secondary metabolites (phenylpropanoid biosynthesis), defense mechanisms, and large enzyme families mechanisms. Notably, the AP2/ERF-ERF, NAC, WRKY, MYB, C2H2, and bHLH transcription factors participated in rice’s cold–stress response and tolerance. On the other hand, we mapped the identified DEGs to 44 published cold–stress-related genes and 41 cold-tolerant Meta-QTLs regions. Of them, 12 DEGs were the published cold–stress-related genes and 418 DEGs fell into the cold-tolerant Meta-QTLs regions. In this study, the identified DEGs and the putative molecular regulatory network can provide insights for understanding the mechanism of cold stress tolerance in rice. In addition, DEGs in KEGG term-enriched terms or cold-tolerant Meta-QTLs will help to secure key candidate genes for further functional studies on the molecular mechanism of cold stress response in rice.

Understanding the early cold response mechanism in IR64 indica rice variety through comparative transcriptome analysis

BackgroundCellular reprogramming in response to environmental stress involves alteration of gene expression, changes in the protein and metabolite profile for ensuring better stress management in plants. Similar to other plant species originating in tropical and sub-tropical areas, indica rice is highly sensitive to low temperature that adversely affects its growth and grain productivity. Substantial work has been done to understand cold induced changes in gene expression in rice plants. However, adequate information is not available for early gene expression, especially in indica variety. Therefore, a transcriptome profile was generated for cold shock treated seedlings of IR64 variety to identify early responsive genes.ResultsThe functional annotation of early DEGs shows enrichment of genes involved in altered membrane rigidity and electrolytic leakage, the onset of calcium signaling, ROS generation and activation of stress responsive transcription factors in IR64. Gene regulatory network suggests that cold shock induced Ca2+ signaling activates DREB/CBF pathway and other groups of transcription factors such as MYB, NAC and ZFP; for activating various cold-responsive genes. The analysis also indicates that cold induced signaling proteins like RLKs, RLCKs, CDPKs and MAPKK and ROS signaling proteins. Further, several late-embryogenesis-abundant (LEA), dehydrins and low temperature-induced-genes were upregulated under early cold shock condition, indicating the onset of water-deficit conditions. Expression profiling in different high yielding cultivars shows high expression of cold-responsive genes in Heera and CB1 indica varieties. These varieties show low levels of cold induced ROS production, electrolytic leakage and high germination rate post-cold stress, compared to IR36 and IR64. Collectively, these results suggest that these varieties may have improved adaptability to cold stress.ConclusionsThe results of this study provide insights about early responsive events in Oryza sativa l.ssp. indica cv IR64 in response to cold stress. Our data shows the onset of cold response is associated with upregulation of stress responsive TFs, hydrophilic proteins and signaling molecules, whereas, the genes coding for cellular biosynthetic enzymes, cell cycle control and growth-related TFs are downregulated. This study reports that the generation of ROS is integral to the early response to trigger the ROS mediated signaling events during later stages.

Transcriptome profiling of Plumbago auriculata Lam. in response to cold stress

With its rare and naturally blue corolla, Plumbago auriculata Lam. has received attention and been introduced and planted worldwide. However, it is sensitive to low temperatures. Continuous low temperatures cause the stagnation of plant growth and the disappearance of ornamental traits. Currently, there is no report on the response of P. auriculata to low temperature. In this study, the chlorophyll fluorescence parameters of P. auriculata leaves were analysed after 10 days of low-temperature stress, and 943 differentially expressed genes were identified via high-throughput RNA sequencing. P. auriculata copes with low-temperature stress by changing the pathways of sugar metabolism, glutathione metabolism and lipid metabolism; however, the decrease in the assimilation level caused by damage to the photoreaction system is an important reason for plant growth stagnation. In addition, we identified 47 differentially expressed transcription factors, including the upregulated MYBS3 transcription factor, which is involved in the MYBS3-dependent pathway that is distinct from the DREB/CBF pathway. Our data reveal the cause of P. auriculata stagnation at low temperatures and provide valuable information for further studies on cold-response mechanisms and the genetic improvement of cold tolerance in P. auriculata.

An eggplant SmICE1a gene encoding MYC-type ICE1-like transcription factor enhances freezing tolerance in transgenic Arabidopsis thaliana.

Low temperature is a crucial environmental factor affecting the quality and production of eggplant. Therefore, it is necessary to explore the molecular mechanisms of low temperature response. We isolated an ICE (inducer of CBF expression) gene from Solanum melongena, named SmICE1a. We then analysed structure, transcriptional activity and expression patterns of SmICE1a. Moreover, we also expressed SmICE1a in Arabidopsis thaliana. Bioinformatics and expression analysis showed that SmICE1a has a typical S-rich motif, ZIP region, bHLH and ACT-like domain. The gene SmICE1a had transcriptional activity in yeast and was localized to the nucleus following transient expression in tobacco leaves, which suggests that SmICE1a is a transcription factor. A dual-LUC assay revealed that SmICE1a can enhance expression of SmCBF. Overexpression of SmICE1a in Arabidopsis increased freezing tolerance and caused multiple biochemical changes: transgenic lines have higher proline content and lower electrolyte leakage and malondialdehyde than the wild type in cold conditions. The expression of AtCBF and their target genes, AtCOR15A, AtCOR47, AtKIN1 and AtRD29A, were up-regulated in SmICE1a-overexpressing plants under low temperatures. Based on these results, we suggest that SmICE1a plays an important role in cold response, which may help to understand the cold response mechanism in eggplant and could be used to enhance cold tolerance of eggplant in future.

The ethylene responsive factor CdERF1 from bermudagrass (Cynodon dactylon) positively regulates cold tolerance

Cold stress is one of the major environmental factors that limit growth and utilization of bermudagrass [Cynodon dactylon (L.) Pers], a prominent warm-season turfgrass. However, the molecular mechanism of cold response in bermudagrass remains largely unknown. In this study, we characterized a cold-responsive ERF (ethylene responsive factor) transcription factor, CdERF1, from bermudagrass. CdERF1 expression was induced by cold, drought and salinity stresses. The CdERF1 protein was nucleus-localized and encompassed transcriptional activation activity. Transgenic Arabidopsis plants overexpressing CdERF1 showed enhanced cold tolerance, whereas CdERF1-underexpressing bermudagrass plants via virus induced gene silencing (VIGS) method exhibited reduced cold resistance compared with control, respectively. Under cold stress, electrolyte leakage (EL), malondialdehyde (MDA), H2O2 and O2− contents were reduced, while the activities of SOD and POD were elevated in transgenic Arabidopsis. By contrast, these above physiological indicators in CdERF1-underexpressing bermudagrass exhibited the opposite trend. To further explore the possible molecular mechanism of bermudagrass cold stress response, the RNA-Seq analyses were performed. The result indicated that overexpression of CdERF1 activated a subset of stress-related genes in transgenic Arabidopsis, such as CBF2, pEARLI1 (lipid transfer protein), PER71 (peroxidase) and LTP (lipid transfer protein). Interestingly, under-expression of CdERF1 suppressed the transcription of many genes in CdERF1-underexpressing bermudagrass, also including pEARLI1 (lipid transfer protein) and PER70 (peroxidase). All these results revealed that CdERF1 positively regulates plant cold response probably by activating stress-related genes, PODs, CBF2 and LTPs. This study also suggests that CdERF1 may be an ideal candidate in the effort to improve cold tolerance of bermudagrass in the further molecular breeding.

Regulation mechanisms of positive cold tolerance in Mongolian sheep

Abstract Mongolian sheep survive well on the Mongolian plateau during tremendously cold winters, but their cold response mechanisms are not well understood. By comparing with Dorper sheep originating from South Africa, we expected to reveal the cold tolerance mechanisms of Mongolian sheep on the basis of transcriptome data, further providing molecular evidence for the targeted breeding of sheep. Based on the mRNA data of RNA-seq, we selected candidate genes among the differentially expressed genes; 7 from adipose tissue, 33 from skeletal muscle, and 10 from the liver. According to enriched KEGG pathways and previous research results, the effects of the above candidate genes mainly involved weakening the synthesis of long-chain fatty acids, raising the adaptive thermogenesis and browning adipogenesis in fat, reducing glucose 6-phosphate, stimulating citrulline generation and enhancing lipid metabolism in skeletal muscle, and postponing cell senescence in the liver. The findings also demonstrate the regulation mechanisms of cold tolerance in different tissues of Mongolian sheep.

Transcriptome profiling of Prunus persica branches reveals candidate genes potentially involved in freezing tolerance

Peach (Prunus persica var.) is an important fruit tree species. Dingjiaba Liguangtao is an excellent cold-tolerant variety of peach. To understand the cold-adaptive mechanism of this peach variety, we analyzed the physiochemical and transcriptomic changes of this cultivar under different low temperature conditions. The results showed that cold stress induced the accumulation of soluble sugar, soluble protein and proline. The increased contents of these compounds enhanced the cold tolerance of Dingjiaba Liguangtao, as indicated by the relatively lower and stable levels of electrolyte leakage index (ELI) and malondialdehyde (MDA) (regardless of the higher value of MDA at −20 °C) before the temperature was decreased to below −25 °C. Meanwhile, the antioxidant enzymes peroxidase (POD) and superoxide dismutase (SOD) also play a role in mitigating the damage caused by cold stress in Dingjiaba Liguangtao. Transcriptomes of samples treated at −5 °C, −15 °C, −25 °C and −35 °C, respectively, were generated and characterized. In total, 890 differentially expressed genes (DEGs) were identified, including 693 upregulated genes and 197 downregulated genes. These genes were enriched in 38 Gene Ontology (GO) terms and 24 clusters of orthologous groups (COG) involved in 64 Kyoto Encyclopedia of Genes and Genomes (KEGG)-defined pathways. DEGs related to signal transduction, carbohydrates and lipid metabolism were significantly enriched. In total, 124 transcription factors belonging to 24 families were found to be cold-responsive. Notably, the largest gene family was the AP2/ERF gene family followed by MYB and NAC. Taken together, these results provide a better understanding of the cold-adaptive mechanism functioning in this excellent cold-tolerant peach species. The unique DEGs identified in this study provide useful information for further study on cold response mechanisms and genetic enhancement of cold resistance in Prunus persica.

Zoysia japonica MYC type transcription factor ZjICE1 regulates cold tolerance in transgenic Arabidopsis

ICE1 (Inducer of CBF Expression 1) is a regulator of cold-induced transcriptome, which plays an important role in plant cold response pathway. To enhance the cold tolerance of Zoysia japonica, one of the warm-season turfgrasses, it is helpful to understand the cold response mechanism in Zoysia japonica. We identified stress-responsive ZjICE1 from Zoysia japonica and characterized its function in cold stress. Our results showed that ZjICE1 shared the typical feature of ICE homolog proteins belonging to a nucleic protein. Transactivation activity assay revealed that ZjICE1 bound to the MYC cis-element in the ZjDREB1’s promotor. The ZjICE1 overexpressed transgenic Arabidopsis showed enhanced tolerance to cold stress with an increases in SOD, POD, and free proline content and reduction in MDA content. They also induced the transcripts abundance of cold-responsive genes (CBF1, CBF2, CBF3, COR47A, KIN1, and RD29A) after cold treatment. These results suggest that ZjICE1 is a positive regulator in Zoysia japonica plant during cold stress and can be a useful gene for the molecular breeding program to develop the cold tolerant zoysiagrass. Furthermore, the ZjICE1 also conferred resistance to salt and drought stresses, providing the better understanding of the basic helix-loop-helix (bHLH) gene family in abiotic stress responses.