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Summary: B‐box (BBX) proteins are an important class of zinc finger transcription factors that play a critical role in plant growth and stress response. However, the mechanisms of how BBX proteins participate in the cold response in tomato remain unclear.Here, using approaches of reverse genetics, biochemical and molecular biology we characterized a BBX transcription factor, SlBBX17, which positively regulates cold tolerance in tomato (Solanum lycopersicum).Overexpressing SlBBX17 enhanced C‐repeat binding factor (CBF)‐dependent cold tolerance in tomato plants, whereas silencing SlBBX17 increased plant susceptibility to cold stress. Crucially, the positive role of SlBBX17 in CBF‐dependent cold tolerance was dependent on ELONGATED HYPOCOTYL5 (HY5). SlBBX17 physically interacted with SlHY5 to directly promote the protein stability of SlHY5 and subsequently increased the transcriptional activity of SlHY5 on SlCBF genes under cold stress. Further experiments showed that cold‐activated mitogen‐activated protein kinases, SlMPK1 and SlMPK2, also physically interact with and phosphorylate SlBBX17 to enhance the interaction between SlBBX17 and SlHY5, leading to enhanced CBF‐dependent cold tolerance.Collectively, the study unveiled a mechanistic framework by which SlMPK1/2‐SlBBX17‐SlHY5 regulated transcription of SlCBFs to enhance cold tolerance, thereby shedding light on the molecular mechanisms of how plants respond to cold stress via multiple transcription factors. [ABSTRACT FROM AUTHOR]

Most cultivars of Vitis vinifera L. are very sensitive to cold. As an exogenous protectant, Biodegradable Liquid Film (BLF) is considered to protect winegrapes from low temperatures and dry winds for safe overwintering. This study aimed to reveal the physiological and biochemical mechanisms of BLF regulating the freezing tolerance of wine grapes. Groups of ten-year-old vines (Cabernet Sauvignon) were sprayed with BLF in November 2020 and 2021, or left untreated as a control treatment, and field plant mortality after overwintering were investigated. Branch samples were collected monthly for determination of biochemical indicators. Dormant two-year-old cuttings (Cabernet Sauvignon) were also used for the determination of relative expression levels of key genes. The results showed that the application of BLF reduced the branch semi-lethal temperature in January and February samples compared with control, and reduced the mortality of above-ground parts, branches and buds. The physiological status of shoots was greatly affected by the climatic conditions of the year, but BLF treatment increased the levels of soluble protein and soluble sugar, and also decreased the content of superoxide anion and malondialdehyde at most sampling times. Correlation analysis showed that the differences in freezing tolerance between BLF and no treated overwintering(CK) vines were mainly related to peroxidase activity, soluble sugar, reducing sugar and starch content. Low temperature stress activated the over expression of ICE1, CBF1, and CBF3, especially for 12h. BLF treatment significantly increased the expression levels of CBF1 and CBF3 under low temperature stress. Overall, these results demonstrate that BLF treatment protects vines from freezing damage by upregulating osmo-regulatory substances and alleviating oxidative damage. [ABSTRACT FROM AUTHOR]

Natural Rubber (NR)-producing guayule (Parthenium argentatum Gray) has been developed as a new crop to diversify NR production. Guayule NR is mainly synthesized in its stem and is upregulated by cold temperatures. A guayule C-repeat binding factor 4 (PaCBF4) was highly expressed in cold-treated stem tissue, coinciding with active rubber biosynthesis and accumulation. Sequence alignments of PaCBF4 with other CBFs indicated that PaCBF4 contains DNA-binding domains responsible for regulating cold-regulated (COR) gene expression. Spatial gene expression profiling of PaCBF4 revealed that stems had the highest expression level among different organs examined. We further confirmed the function of PaCBF4 as regulator of cold-signaling processes by expressing it in the model plant Arabidopsis under a constitutive ubiquitin promoter from potato. The resulting transgenic Arabidopsis lines expressing PaCBF4 turned on expression of a set of Arabidopsis COR genes under both room (24ºC) and cold (4ºC) temperatures, in contrast to the wild-type Arabidopsis that expressed these COR genes solely upon cold treatment. Furthermore, the transgenic plants displayed enhanced freezing tolerance at −5ºC, exhibiting a survival rate of 88–98% compared with 0% survival rate of wild-type plants. Our results suggest that PaCBF4 is a functional member of the guayule CBF gene family and plays a significant role in cold and freeze tolerance. Interestingly, overexpressing PaCBF4 in Arabidopsis did not affect the normal phenotype of the plant during vegetative and inflorescence growth, but the gene led to more undeveloped siliques after flowering. • A guayule C-repeat binding factor 4 (PaCBF4) has CBF signature DNA binding domains. • PaCBF4 was highly expressed in stem and induced by cold and freezing temperatures. • Arabidopsis expressing PaCBF4 had constitutive expression of cold-regulated genes. • Transgenic Arabidopsis expressing PaCBF4 demonstrated increased freezing tolerance. • Transgenic Arabidopsis expressing PaCBF4 had an undeveloped silique phenotype. [ABSTRACT FROM AUTHOR]

Cold stress limits plant geographical distribution and influences plant growth, development, and yields. Plants as sessile organisms have evolved complex biochemical and physiological mechanisms to adapt to cold stress. These mechanisms are regulated by a series of transcription factors and proteins for efficient cold stress acclimation. It has been established that the ICE-CBF-COR signaling pathway in plants regulates how plants acclimatize to cold stress. Cold stress is perceived by receptor proteins, triggering signal transduction, and Inducer of CBF Expression (ICE) genes are activated and regulated, consequently upregulating the transcription and expression of the C-repeat Binding Factor (CBF) genes. The CBF protein binds to the C-repeat/Dehydration Responsive Element (CRT/DRE), a homeopathic element of the Cold Regulated genes (COR gene) promoter, activating their transcription. Transcriptional regulations and post-translational modifications regulate and modify these entities at different response levels by altering their expression or activities in the signaling cascade. These activities then lead to efficient cold stress tolerance. This paper contains a concise summary of the ICE-CBF-COR pathway elucidating on the cross interconnections with other repressors, inhibitors, and activators to induce cold stress acclimation in plants.

Abstract Although rye is one of the most cold-tolerant species among temperate cereals, its huge and complex genome has prevented us from identifying agronomically useful genes. However, advances in high-throughput sequencing technology are making it increasingly possible to investigate its genome. The C - repeat binding factor (CBF) gene family controls cold tolerance in plants and its members are well conserved among eudicots and monocots, among which there are diverse homologs. Despite its large genome, only a small number of CBF genes have been identified in rye. In this study, we explored high-throughput sequencing data of the rye genome and identified 12 novel CBF genes. Sequence analyses revealed that these genes contain signature sequences of the CBF family. Chromosomal localization of the genes by PCR using wheat–rye addition lines showed that most of these are located on the long arm of chromosome 5, but also on the long arm of chromosomes 2 and 6. On the basis of comparative analyses of CBF family members in the Triticeae, CBF proteins were divided into several groups according to phylogenetic relationship and conserved motifs. Light is essential to fully induce CBF gene expression and there is specificity in the response to different types of abiotic stresses in ScCBF genes. The results of our study will assist investigations of CBF genes in the Triticeae and the mechanism of cold tolerance through the CBF-dependent pathway in plants. Highlights • 12 new CBF genes and five new CBF gene alleles in rye were identified. • Cis -elements, conserved motifs and phylogenetic tree were analyzed. • The expressions of the CBF genes under abiotic stresses depending on diurnal cycle were examined. • CBF genes in the Triticeae were genetically and physically mapped. [ABSTRACT FROM AUTHOR]

Changes in the stomatal aperture in response to CO2 levels allow plants to manage water usage, optimize CO2 uptake and adjust to environmental stimuli. The current study reports that sub-ambient CO2 up-regulated the low temperature induction of the C-repeat Binding Factor (CBF)-dependent cold signaling pathway in Arabidopsis (Arabidopsis thaliana) and the opposite occurred in response to supra-ambient CO2. Accordingly, cold induction of various downstream cold-responsive genes was modified by CO2 treatments and expression changes were either partially or fully CBF-dependent. Changes in electrolyte leakage during freezing tests were correlated with CO2′s effects on CBF expression. Cold treatments were also performed on Arabidopsis mutants with altered stomatal responses to CO2, i.e., high leaf temperature 1-2 (ht1-2, CO2 hypersensitive) and β-carbonic anhydrase 1 and 4 (ca1ca4, CO2 insensitive). The cold-induced expression of CBF and downstream CBF target genes plus freezing tolerance of ht1-2 was consistently less than that for Col-0, suggesting that HT1 is a positive modulator of cold signaling. The ca1ca4 mutant had diminished CBF expression during cold treatment but the downstream expression of cold-responsive genes was either similar to or greater than that of Col-0. This finding suggested that βCA1/4 modulates the expression of certain cold-responsive genes in a CBF-independent manner. Stomatal conductance measurements demonstrated that low temperatures overrode low CO2-induced stomatal opening and this process was delayed in the cold tolerant mutant, ca1ca4, compared to the cold sensitive mutant, ht1-2. The similar stomatal responses were evident from freezing tolerant line, Ox-CBF, overexpression of CBF3, compared to wild-type ecotype Ws-2. Together, these results indicate that CO2 signaling in stomata and CBF-mediated cold signaling work coordinately in Arabidopsis to manage abiotic stress.

Main conclusion Evergreen plants are more vulnerable than grasses and birch to snow and temperature variability in the sub-Arctic. Most Arctic climate impact studies focus on single factors, such as summer warming, while ecosystems are exposed to changes in all seasons. Through a combination of field and laboratory manipulations, we compared physiological and growth responses of dominant sub-Arctic plant types to midwinter warming events (6 °C for 7 days) in combination with freezing, simulated snow thaw and nitrogen additions. We aimed to identify if different plant types showed consistent physiological, cellular, growth and mortality responses to these abiotic stressors. Evergreen dwarf shrubs and tree seedlings showed higher mortality (40-100%) following extreme winter warming events than Betula pubescens tree seedlings and grasses (0-27%). All species had growth reductions following exposure to - 20 °C, but not all species suffered from - 10 °C irrespective of other treatments. Winter warming followed by - 20 °C resulted in the greatest mortality and was strongest among evergreen plants. Snow removal reduced the biomass for most species and this was exacerbated by subsequent freezing. Nitrogen increased the growth of B. pubescens and grasses, but not the evergreens, and interaction effects with the warming, freezing and snow treatments were minor and few. Physiological activity during the winter warming and freezing treatments was inconsistent with growth and mortality rates across the plants types. However, changes in the membrane fatty acids were associated with reduced mortality of grasses. Sub-Arctic plant communities may become dominated by grasses and deciduous plants if winter snowpack diminishes and plants are exposed to greater temperature variability in the near future. [ABSTRACT FROM AUTHOR]

Key message: This work contributes to the identification and understanding of CBF genes and their putative role in the mechanisms of cold tolerance in eucalypt species. Abstract: Three new CBF genes were isolated from E. globulus-denominated Egl CBF1a, c, and d, coding for proteins of 220, 229, and 196 amino acids, respectively. The sequence analysis showed that the three predicted proteins contain an AP2 DNA-binding domain and two CBF signature sequences. Phylogenetic analysis demonstrated that these proteins were highly similar to those described in E. grandis and E. gunnii. Transcript abundance analysis in three different E. globulus genotypes exposed to a cold acclimation treatment showed that these CBF genes were highly related to the acclimation process and presented the highest relative expression at freezing temperatures. Egl CBF1a showed the highest expression level (1311-fold change) in the cold-tolerant genotype (R1). Egl CBF1a and d genes were induced by chilling and freezing temperatures, while Egl CBF1c was constitutively expressed, increasing its transcript level when plants were exposed to freezing temperatures. The constitutive overexpression of each E. globulus CBF gene in Arabidopsis plants induces the endogenous CBF regulon gene expression of Arabidopsis and enhanced its tolerance to freezing, with additional phenotypic effects including growth inhibition and delayed flowering. These results indicate that the three Egl CBF genes analyzed play important roles under cold acclimation processes in E. globulus and are involved in the signaling pathway of cold stress and the freezing tolerance phenotype observed on specific genotypes of this species and in transgenic Arabidopsis lines. [ABSTRACT FROM AUTHOR]

C-repeat binding factors (CBFs) play a key role in abiotic stresses. However, little is known about CBFs in Populus euphratica. Here, we isolated PeCBF4a, a member of CBF gene family from P. euphratica. Its expression was induced by dehydration, salinity and low temperature. We generated transgenic poplars ( Populus tomentosa 'YiXianCiZhu B385') overexpressing PeCBF4a (OE-PeCBF4a) under the control of the CaMV 35S promoter or transformed with empty vector. The wild-type (WT) and empty vector lines were used as controls. Under abiotic stresses, the photosynthetic rate (Pn) of 60-day-old OE-PeCBF4a lines increased 34.7-165.7 % and the instantaneous water use efficiency (iWUE) increased 48.9-103.7 % over controls. The maximum quantum efficiency of PSII photochemistry (Fv/Fm) values in PeCBF4a-overexpressing lines did not change significantly and were 2.14-5.89 % higher. The non-photochemical quenching coefficient (NPQ) mean of OE-PeCBF4a lines decreased by 12.02-23.64 % while the photochemical quenching (qP) value was 8.75-22.31 % higher than controls. OE-PeCBF4a lines also displayed higher superoxide dismutase (SOD) activities and markedly lower malondialdehyde (MDA) levels compared to controls. Higher levels of proline and sugars accumulated in transgenic plants. Overexpression of PeCBF4a not only induced strong expression of the stress-responsive downstream target genes of PeCBF4a, PtRCI2A (rare-cold-inducible 2A) and PtDI21 (drought-induced 21), but also caused dwarfed phenotypes. Based on results from P-V curve measurements, the osmotic adjustment capability of OE-PeCBF4a plants was enhanced. These results confirmed that OE-PeCBF4a poplars exhibit greater tolerance to stress, indicating that PeCBF4a plays a positive role in stress tolerance. [ABSTRACT FROM AUTHOR]

Plants growth and development are adversely affected by various abiotic stresses. Water and temperature plays important role on plant growth and crop yield. C-repeat binding factor (CBF) acts as transcription factor in plant that involve in cold-response pathway. It has major role in cold acclimation and cold response gene expression. An Agrobacterium -mediated transformation system has been established for introducing foreign gene into bottle gourd. We have introduced Arabidopsis CBF3/DREB1A gene into bottle gourd ( Lageneraria siceraria Standl.) using Agrobacterium -mediated transformation. Experimental results confirmed that transgenic plants were better cold resistant than non-transgenic plants and CBF3/DREB1A gene was not transferred to stem, leaf and fruit of the grafted watermelon ( Citrullus lanatus var. lanatus ) from transgenic bottle gourd rootstock. Horticultural traits were similar for transgenic and non-transgenic plants. We concluded that the rootstock of transgenic bottle gourd might be used for growing watermelon at low soil temperature. [ABSTRACT FROM AUTHOR]

The interaction of heat stress with internal signaling networks was investigated through Arabidopsis thaliana mutants that were deficient in either tocopherols (vte1 mutant) or non-photochemical fluorescence quenching (NPQ; npq1, npq4, and npq1 npq4 mutants). Leaves of both vte1 and npq1 npq4 mutants that developed at a high temperature exhibited a significantly different leaf vascular organization compared to wild-type Col-0. Both mutants had significantly smaller water conduits (tracheary elements) of the xylem, but the total apparent foliar water-transport capacity and intrinsic photosynthetic capacity were similarly high in mutants and wild-type Col-0. This was accomplished through a combination of more numerous (albeit narrower) water conduits per vein, and a significantly greater vein density in both mutants relative to wild-type Col-0. The similarity of the phenotypes of tocopherol-deficient and NPQ-deficient mutants suggests that leaf vasculature organization is modulated by the foliar redox state. These results are evaluated in the context of interactions between redox-signaling pathways and other key regulators of plant acclimation to growth temperature, such as the C-repeat binding factor (CBF) transcription factors, several of which were upregulated in the antioxidant-deficient mutants. Possibilities for the future manipulation of the interaction between CBF and redox-signaling networks for the purpose of cooptimizing plant productivity and plant tolerance to extreme temperatures are discussed.

The evolutionary processes and genetics underlying local adaptation at a specieswide level are largely unknown. Recent work has indicated that a frameshift mutation in a member of a family of transcription factors, C-repeat binding factors or CBFs, underlies local adaptation and freezing tolerance divergence between two European populations of Arabidopsis thaliana. To ask whether the specieswide evolution of CBF genes in Arabidopsis is consistent with local adaptation, we surveyed CBF variation from 477 wild accessions collected across the species' range. We found that CBF sequence variation is strongly associated with winter temperature variables. Looking specifically at the minimum temperature experienced during the coldest month, we found that Arabidopsis from warmer climates exhibit a significant excess of nonsynonymous polymorphisms in CBF genes and revealed a CBF haplotype network whose structure points to multiple independent transitions to warmer climates. We also identified a number of newly described mutations of significant functional effect in CBF genes, similar to the frameshift mutation previously indicated to be locally adaptive in Italy, and find that they are significantly associated with warm winters. Lastly, we uncover relationships between climate and the position of significant functional effect mutations between and within CBF paralogs, suggesting variation in adaptive function of different mutations. Cumulatively, these findings support the hypothesis that disruption of CBF gene function is adaptive in warmer climates, and illustrate how parallel evolution in a transcription factor can underlie adaptation to climate. [ABSTRACT FROM AUTHOR]

Low temperature as one of the most important environmental factors limits the productivity of plants across the world. Aegilops, as a wild species of Poaceae, contains low temperature-responsive genes. In this study, we analyzed morphological (wilting, chlorosis, and recovery) and physiological (ion leakage) characteristics to identification of a cold-tolerant genotype. In this experiment, we introduced two transcription factors (TFs) in Aegilops species for the first time. Bioinformatics analysis demonstrated that our nucleotide sequences have high similarity with CBF14 (C-repeat-binding factor) and NAC2 (NAM, ATAF, and CUC) in Triticum aestivum. Based on the physiological and morphological data, one genotype (Aladizgeh) was identified as the most resistant genotype which was selected for further gene expression analysis. The real-time PCR results indicated that the CBF14 gene was not expressed 3 h following cold treatment, but the highest expression was observed after 6, 12, and 24 h of cold treatment; however, a sudden decrease was observed in its expression after 30 h. The NAC2 gene also was not expressed 3 h after cold stress, but the highest expression was at 24 h and similar to the CBF14 gene; its expression suddenly decreased after 30 h. Our results indicated that this genotype can tolerate −4 °C for 3 h, but the CBF14 and NAC2 genes were activated when treated for longer durations. Expression of TFs studied in this experiment had decreased after 30 h, in which cell death seems to be the important reason. [ABSTRACT FROM AUTHOR]

C-repeat binding factor (CBF) signaling pathway is involved in cold acclimation responsive to low temperature and some other stresses. CBF transcription factor family is the key component of this pathway. In this study, eight CBF-like genes, BrCBF1, BrCBF2, BrCBF3, BrCBF4, BrCBF5, and BrCBF6A/B/C were isolated from non-heading Chinese cabbage ( Brassica campestris ssp. chinensis L. Makino, NHCC). The deduced CBF proteins shared high similarity with their Arabidopsis orthologs and localized to the nucleus. Furthermore, quantitative real-time PCR (qPCR) analysis showed that BrCBF1~ 3 were induced by cold (4 °C) but not drought or abscisic acid (ABA), indicating that they are involved in an ABA-independent pathway; however, BrCBF4~ 6 were regulated by both drought and ABA, suggesting that they were involved in an ABA-dependent pathway. Nevertheless, unlike Arabidopsis, BrCBF4~ 6 showed response to both cold and ABA, indicates ABA-independent and ABA-dependent parts of CBF pathway in NHCC might not be completely separate, and these genes may act as the connection points in the network. BrCBFs were also accumulated in response to salicylic acid (SA), methyljasmonate (MeJA), and ethylene (ET), indicating that BrCBF genes might participate in the response to biotic stresses. Taken together, eight CBF genes were isolated from NHCC which compose a functional CBF signaling pathway by participating in response to multiple stresses and performing roles from Arabidopsis to some extent. [ABSTRACT FROM AUTHOR]

Cassava ( Manihot esculenta Crantz) is a tropical and subtropical plant and susceptible to chilling injury. In this research, a C-repeat binding factor ( CBF)-like gene (GenBank accession number JQ339740) has been isolated from cassava, and named as MeCBF1. The full-length DNA of MeCBF1 is 1,037 base pair (bp), without intron. The 5′ untranslated region is 102 bp, the 3′ untranslated region is 239 bp, and the open reading frame is 696 bp encoding 231 amino acids. The deduced amino acid sequence of MeCBF1 contains two CBF conserved motifs of PKK(P/R)AGRxKFxETRHP and DSxWR. The MeCBF1 shows 83 % homology to the CRT/DRE binding factor 1 from Hevea brasiliensis (Accession no. AAY43213.1). However, in cassava, the MeCBF1 target genes showed low similarity to the CBF/DREB regulated genes in Arabidopsis thaliana. Quantitative real-time PCR showed that the MeCBF1 was highly expressed in stems and leaves, and lowly expressed in roots. In addition, the expression of the MeCBF1 quickly responded to low temperature stress (4 °C). These results suggest that, the MeCBF1 is functional in cassava. Further studies on the MeCBF1 might be helpful to reveal molecular mechanism of cassava's high sensitivity to low temperature. [ABSTRACT FROM AUTHOR]

Most cultivars of Vitis vinifera L. are very sensitive to cold. As an exogenous protectant, Biodegradable Liquid Film (BLF) is considered to protect winegrapes from low temperatures and dry winds for safe overwintering. This study aimed to reveal the physiological and biochemical mechanisms of BLF regulating the freezing tolerance of wine grapes. Groups of ten-year-old vines (Cabernet Sauvignon) were sprayed with BLF in November 2020 and 2021, or left untreated as a control treatment, and field plant mortality after overwintering were investigated. Branch samples were collected monthly for determination of biochemical indicators. Dormant two-year-old cuttings (Cabernet Sauvignon) were also used for the determination of relative expression levels of key genes. The results showed that the application of BLF reduced the branch semi-lethal temperature in January and February samples compared with control, and reduced the mortality of above-ground parts, branches and buds. The physiological status of shoots was greatly affected by the climatic conditions of the year, but BLF treatment increased the levels of soluble protein and soluble sugar, and also decreased the content of superoxide anion and malondialdehyde at most sampling times. Correlation analysis showed that the differences in freezing tolerance between BLF and no treated overwintering(CK) vines were mainly related to peroxidase activity, soluble sugar, reducing sugar and starch content. Low temperature stress activated the over expression of ICE1 , CBF1 , and CBF3 , especially for 12h. BLF treatment significantly increased the expression levels of CBF1 and CBF3 under low temperature stress. Overall, these results demonstrate that BLF treatment protects vines from freezing damage by upregulating osmo-regulatory substances and alleviating oxidative damage., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Han, Yao, Xue, Wang, Wang, Cao, Hui, Wu, Li, Wang and Li.)

Freezing temperatures can be devastating for annual bedding plants, including Petunia × hybrida (petunia). The C-repeat binding factor (CBF) transcriptional activator proteins induce expression of a cascade of genes during the process of cold acclimation that results in a transient improvement in freezing tolerance for many plant species. Petunia 'Mitchell' plants were transformed with either AtCBF3 from Arabidopsis thaliana or SlCBF1 from Solanum lycopersicum, both under the strong constitutive CaMV 35S promoter. AtCBF3, but not SlCBF1, expression improved basal (non-cold-acclimated) freezing tolerance compared to wild-type plants, and induced expression of putative members of a petunia CBF-regulon. The basal freezing tolerance of AtCBF3 lines was similar to cold-acclimated freezing tolerance for wild-type plants. Additionally, freezing tolerance of AtCBF3 lines improved further following cold acclimation. Constitutive AtCBF3 expression also resulted in a dwarf phenotype, with reductions in plant height, internode length and leaf area, but did not impact leaf mass, resulting in a decreased specific leaf area (mm mg). Flowering of AtCBF3 lines was also delayed compared to wild-type. [ABSTRACT FROM AUTHOR]

Cold stress limits plant geographical distribution and influences plant growth, development, and yields. Plants as sessile organisms have evolved complex biochemical and physiological mechanisms to adapt to cold stress. These mechanisms are regulated by a series of transcription factors and proteins for efficient cold stress acclimation. It has been established that the ICE-CBF-COR signaling pathway in plants regulates how plants acclimatize to cold stress. Cold stress is perceived by receptor proteins, triggering signal transduction, and Inducer of CBF Expression (ICE) genes are activated and regulated, consequently upregulating the transcription and expression of the C-repeat Binding Factor (CBF) genes. The CBF protein binds to the C-repeat/Dehydration Responsive Element (CRT/DRE), a homeopathic element of the Cold Regulated genes (COR gene) promoter, activating their transcription. Transcriptional regulations and post-translational modifications regulate and modify these entities at different response levels by altering their expression or activities in the signaling cascade. These activities then lead to efficient cold stress tolerance. This paper contains a concise summary of the ICE-CBF-COR pathway elucidating on the cross interconnections with other repressors, inhibitors, and activators to induce cold stress acclimation in plants. [ABSTRACT FROM AUTHOR]

Abstract: Soybean (Glycine max) is a relatively cold intolerant plant. In most stress tolerant plants the responsive expression of dehydrin proteins in vegetative tissues can be a significant contributor to protection against environmental stresses. The purpose of this study was to examine the expression of dehydrins in various organs and the cold-responses of dehydrin genes in vegetative tissues of soybean. Examination of the soybean genome indicated the presence of genes encoding ten distinct dehydrins. Levels of dehydrin proteins were probed with several antibodies specific to dehydrins or to the signature K-sequence. A single vegetatively expressed dehydrin protein was detected and the levels were insignificantly altered in response to cold, drought, or salt stress, nor was the transcript responsive to ABA. This SK2-type, acidic dehydrin family member (GmERD14) was purified, identified by mass spectroscopy, and shown to be in vivo phosphorylated; indicating characteristics similar to other known acidic dehydrins. The lack of cold stress-regulated acidic dehydrin expression may contribute to the inability of soybean to cold acclimate. While transcripts for all ten dehydrins could be detected in various tissues, only three accumulated to significant levels in vegetative tissues (two of the KS type and one of SK2 type). One of these transcripts, a KS dehydrin, was accumulated following cold treatments. The accumulation of the KS dehydrin was also responsive to exogenous ABA. [Copyright &y& Elsevier]

Apart from water availability, low temperature is the most important environmental factor limiting the productivity and geographical distribution of plants across the world. To cope with cold stress, plant species have evolved several physiological and molecular adaptations to maximize cold tolerance by adjusting their metabolism. The regulation of some gene products represents an additional mechanism of cold tolerance. A consequence of these mechanisms is that plants are able to survive exposure to low temperature via a process known as cold acclimation. In this review, we briefly summarize recent progress in research and hypotheses on how sensitive plants perceive cold. We also explore how this perception is translated into changes within plants following exposure to low temperatures. Particular emphasis is placed on physiological parameters as well as transcriptional, post-transcriptional and post-translational regulation of cold-induced gene products that occur after exposure to low temperatures, leading to cold acclimation. [ABSTRACT FROM AUTHOR]

Background: Little is known about the potential of Brachypodium distachyon as a model for low temperature stress responses in Pooideae. The ice recrystallization inhibition protein (IRIP) genes, fructosyltransferase (FST) genes, and many C-repeat binding factor (CBF) genes are Pooideae specific and important in low temperature responses. Here we used comparative analyses to study conservation and evolution of these gene families in B. distachyon to better understand its potential as a model species for agriculturally important temperate grasses. Results: Brachypodium distachyon contains cold responsive IRIP genes which have evolved through Brachypodium specific gene family expansions. A large cold responsive CBF3 subfamily was identified in B. distachyon, while CBF4 homologs are absent from the genome. No B. distachyon FST gene homologs encode typical core Pooideae FST-motifs and low temperature induced fructan accumulation was dramatically different in B. distachyon compared to core Pooideae species. Conclusions: We conclude that B. distachyon can serve as an interesting model for specific molecular mechanisms involved in low temperature responses in core Pooideae species. However, the evolutionary history of key genes involved in low temperature responses has been different in Brachypodium and core Pooideae species. These differences limit the use of B. distachyon as a model for holistic studies relevant for agricultural core Pooideae species. [ABSTRACT FROM AUTHOR]

Abstract: C-repeat binding factor (CBF) is a kind of transcription factor that regulates expression of a number of genes related to abiotic stresses. Three CBF genes were isolated from the genomic DNA of Gossypium hirsutum L. cultivars Gh12 and Gh36 and G. barbadense L. cultivar Gb7124. Cotton CBF gene encodes 184 amino acids, containing the CBF-family signature PKRRAGRKKFQETRHP and FADSAW. Southern blotting result showed that CBF genes were present as the form of gene family in the genome of cotton. Northern blotting result indicated that GbCBF1 was induced by low temperature, drought, salt, and abscisic acid. This gene was constructed into plant expression vector pCambia2301, in which the gene was driven by 35S and NOS promoters separately. Plant expression vectors were then transferred into Nicotiana tabacum L. cultivar NC89 using Agrobacterium-mediated transformation method. Twenty-six transgenic tobacco lines were obtained after kanamycin screening and PCR detection. After PCR and reverse tanscription PCR analyses in partial T1 transgenic plants, the GbCBF1 gene was confirmed to be transcripted and inherit in offspring normally. Under low temperature stress, the electrolytic leakage rate of transgenic tobacco was lower than that of the wild type tobacco; however, free proline and soluble sugar contents of transgenic tobacco were higher than those of the wild type tobacco. This result indicated that GbCBF1 enhances cold tolerance in transgenic tobacco. [Copyright &y& Elsevier]

When leaves are exposed to low temperature, sugars accumulate and transcription factors in the C-repeat binding factor (CBF) family are expressed, which, together with CBF-independent pathways, are known to contribute to the cold acclimation process and an increase in freezing tolerance. What is not known, however, is whether expression of these cold-regulated genes can be induced systemically in response to a localized cold treatment. To address this, pre-existing, mature leaves of warm-grown Arabidopsis thaliana were exposed to a localized cold treatment (near 10°C) whilst conjoined newly developing leaves continued only to experience warmer temperatures. In initial experiments on wild-type A. thaliana (Col-0) using real-time reverse transcription–PCR (RT–PCR) we observed that some genes—including CBF genes, certain downstream cold-responsive (COR) targets and CBF-independent transcription factors—respond to a direct 9°C treatment of whole plants. In subsequent experiments, we found that the treatment of expanded leaves with temperatures near 10°C can induce cold-associated genes in conjoined warm-maintained tissues. CBF1 showed a particularly strong systemic response, although CBF-independent transcription factors also responded. Moreover, the localized cold treatment of A. thaliana (C24) plants with a luciferase reporter fused to the promoter region of KIN2 indicated that in warm-maintained leaves, KIN2 might respond to a systemic signal from remote, directly cold-treated leaves. Collectively, our study provides strong evidence that the processes involved in cold acclimation are partially mediated by a signal that acts systemically. This has the potential to act as an early-warning system to enable developing leaves to cope better with the cold environment in which they are growing. [ABSTRACT FROM PUBLISHER]

• The transcription of PpVIN2 is activated by cold stress. • PpCBF6 can directly bind to the promoter of PpVIN2. • PpCBF6 negatively regulates PpVIN2 gene expression. • Overexpression of PpCBF6 delays the reduction of sucrose content. • Higher PpCBF6 expression in MeJA treatment reduced PpVIN2 increase. PpVIN2 is the only vacuolar invertase (VIN) gene in peaches that is sensitive to cold. PpVIN2 functions in sucrose decomposition and chilling injury (CI), but it is unknown how low temperatures induce PpVIN2. Here, we confirmed low-temperature activation of PpVIN2 transcription from a PpVIN2 promoter using a transgenic tobacco model. C-repeat binding factor (CBF) is a conserved cold-responsive gene in plants, and PpCBF6 expression increases rapidly when peaches suffer from cold stress. We studied the interaction between PpCBF6 and PpVIN2 both in vivo and in vitro. Using yeast one-hybrid assay and electrophoretic mobility shift assay, we confirmed that PpCBF6 binds to the promoter of PpVIN2 , and results from a dual luciferase assay indicate that PpCBF6 inhibits the promoter activity of PpVIN2. In vivo , transient overexpression of PpCBF6 decreases PpVIN2 expression and VIN activity, and increases sucrose levels. In addition, when PpCBF6 is targeted using virus-induced gene silencing (VIGS), PpVIN2 expression and activity increase, accompanied by a decrease in sucrose content. Compared to the control group, exogenous methyl jasmonate (MeJA) treatment caused a higher expression of PpCBF6 , and reduced the rapid rise of PpVIN2 expression level. This resulted in the lower VIN activity and higher sucrose content in MeJA-treated peach fruit, thereby reducing the CI. In general, we proved that PpCBF6 retarded the degradation of sucrose by inhibiting the increased expression of PpVIN2 , which improves the chilling resistance of peach fruit. [ABSTRACT FROM AUTHOR]

Summary: Cold acclimation of plants affects many aspects of metabolism. Changes in plasma membrane lipids have always been considered to be important for development of frost resistance and survival at subzero temperatures. We studied different cultivars of winter wheat (Triticum aestivum L.) that differed in frost resistance induced either by cold acclimation or treatment with the plant hormone abscisic acid (ABA). Plasma membranes were isolated from non-acclimated and cold- as well as from ABA-acclimated plants, and were subjected to detailed lipid analysis. Cold acclimation affected virtually all plasma membrane lipid components and their constituents, resulting in both increases and decreases, which varied between the three groups of plants investigated. Including the cold-induced variations observed in the few plant species studied in detail previously, cerebrosides were the only components reduced by cold acclimation in all plants. In wheat, more uniform and consistent patterns were obtained when considering colligative parameters such as total free sterols, phospholipids or glycolipids, either as the proportion of total lipids or based on plasma membrane protein. The parameter which changed most significantly in parallel to the increase of inducible frost resistance in the three groups of plants was the ratio of free sterols/glycolipids, which increased. ABA treatment resulted in qualitatively similar effects in only one cultivar, but in general these changes were less pronounced. Compared to changes in transcription rates of several cold-induced genes and in the concentration of various compatible solutes reported for other plants, the observed changes in plasma membrane lipids are minor ones. This may indicate that acclimation-induced changes can be accomplished by posttranscriptional regulation of enzymatic activities, which is in agreement with the failure to detect significant changes in transcription of the corresponding genes during cold induction. [Copyright &y& Elsevier]

Abstract Background Little is known about the potential of Brachypodium distachyon as a model for low temperature stress responses in Pooideae. The ice recrystallization inhibition protein (IRIP) genes, fructosyltransferase (FST) genes, and many C-repeat binding factor (CBF) genes are Pooideae specific and important in low temperature responses. Here we used comparative analyses to study conservation and evolution of these gene families in B. distachyon to better understand its potential as a model species for agriculturally important temperate grasses. Results Brachypodium distachyon contains cold responsive IRIP genes which have evolved through Brachypodium specific gene family expansions. A large cold responsive CBF3 subfamily was identified in B. distachyon, while CBF4 homologs are absent from the genome. No B. distachyon FST gene homologs encode typical core Pooideae FST-motifs and low temperature induced fructan accumulation was dramatically different in B. distachyon compared to core Pooideae species. Conclusions We conclude that B. distachyon can serve as an interesting model for specific molecular mechanisms involved in low temperature responses in core Pooideae species. However, the evolutionary history of key genes involved in low temperature responses has been different in Brachypodium and core Pooideae species. These differences limit the use of B. distachyon as a model for holistic studies relevant for agricultural core Pooideae species.

Changes in the stomatal aperture in response to CO2 levels allow plants to manage water usage, optimize CO2 uptake and adjust to environmental stimuli. The current study reports that sub-ambient CO2 up-regulated the low temperature induction of the C-repeat Binding Factor (CBF)-dependent cold signaling pathway in Arabidopsis (Arabidopsis thaliana) and the opposite occurred in response to supra-ambient CO2. Accordingly, cold induction of various downstream cold-responsive genes was modified by CO2 treatments and expression changes were either partially or fully CBF-dependent. Changes in electrolyte leakage during freezing tests were correlated with CO2′s effects on CBF expression. Cold treatments were also performed on Arabidopsis mutants with altered stomatal responses to CO2, i.e., high leaf temperature 1-2 (ht1-2, CO2 hypersensitive) and β-carbonic anhydrase 1 and 4 (ca1ca4, CO2 insensitive). The cold-induced expression of CBF and downstream CBF target genes plus freezing tolerance of ht1-2 was consistently less than that for Col-0, suggesting that HT1 is a positive modulator of cold signaling. The ca1ca4 mutant had diminished CBF expression during cold treatment but the downstream expression of cold-responsive genes was either similar to or greater than that of Col-0. This finding suggested that βCA1/4 modulates the expression of certain cold-responsive genes in a CBF-independent manner. Stomatal conductance measurements demonstrated that low temperatures overrode low CO2-induced stomatal opening and this process was delayed in the cold tolerant mutant, ca1ca4, compared to the cold sensitive mutant, ht1-2. The similar stomatal responses were evident from freezing tolerant line, Ox-CBF, overexpression of CBF3, compared to wild-type ecotype Ws-2. Together, these results indicate that CO2 signaling in stomata and CBF-mediated cold signaling work coordinately in Arabidopsis to manage abiotic stress. [ABSTRACT FROM AUTHOR]

The interaction of heat stress with internal signaling networks was investigated through Arabidopsisthaliana mutants that were deficient in either tocopherols (vte1 mutant) or non-photochemical fluorescence quenching (NPQ; npq1, npq4, and npq1 npq4 mutants). Leaves of both vte1 and npq1 npq4 mutants that developed at a high temperature exhibited a significantly different leaf vascular organization compared to wild-type Col-0. Both mutants had significantly smaller water conduits (tracheary elements) of the xylem, but the total apparent foliar water-transport capacity and intrinsic photosynthetic capacity were similarly high in mutants and wild-type Col-0. This was accomplished through a combination of more numerous (albeit narrower) water conduits per vein, and a significantly greater vein density in both mutants relative to wild-type Col-0. The similarity of the phenotypes of tocopherol-deficient and NPQ-deficient mutants suggests that leaf vasculature organization is modulated by the foliar redox state. These results are evaluated in the context of interactions between redox-signaling pathways and other key regulators of plant acclimation to growth temperature, such as the C-repeat binding factor (CBF) transcription factors, several of which were upregulated in the antioxidant-deficient mutants. Possibilities for the future manipulation of the interaction between CBF and redox-signaling networks for the purpose of cooptimizing plant productivity and plant tolerance to extreme temperatures are discussed. [ABSTRACT FROM AUTHOR]

Temperature is one of the main environmental factors that affect plant metabolism. Considering that plants are sessile, their survival depends on the efficient activation of resistance responses to thermal stress. In this comprehensive review, we discuss recent work on rapid biochemical and physiological adjustments, herein referred to as those occurring during the first few hours or a few days after the beginning of the change in the ambient temperature. The short-term metabolic modulation after plant exposure to heat and cold, including chilling and freezing, is discussed. Effects on photosynthesis, cell membranes, antioxidant system, production of heat shock proteins and nitric oxide, as well as an overview of signaling events to heat or cold stress are presented. In addition, we also discuss the acclimation process that occurs when the plant acquires resistance to an increase or decrease in temperature, adjusting its homeostasis and steady-state physiology to the new temperatures. Finally, we present studies with tropical plants that aim at elucidating the effects of temperature and the identification of the resilience levels of these plants to the expected climate changes, and which seek the development of techniques for germplasm conservation of endangered species.

Proline plays a significant role in plant resistance to abiotic stresses, and its level is determined by a combination of synthesis, catabolism and transport. The primary proteins involved are Δ(1)-pyrroline-5-carboxylate synthetase (P5CS), proline dehydrogenase (PDH) and proline transporter (ProT). To utilise proline metabolism to improve the stress resistance of Chrysanthemum×morifolium, we isolated two P5CS-homologous genes (ClP5CS1 and ClP5CS2), one PDH gene (ClPDH) and four ProT-homologous genes (ClProT1-4) (GenBANK accession numbers: KF743136-KF743142) from Chrysanthemum lavandulifolium, which is closely related to chrysanthemums and exhibits strong resistance to stresses. Expression analysis of these genes in different organs and under various stresses indicated that ClP5CSs showed substantial constitutive expression, while ClPDH was only strongly expressed in the capitulum and was inhibited under most stresses. The expression patterns of four ClProT genes presented characteristics of organ specificity and disparity under stresses. Above all, the expression of ClProT2 was restricted to above-ground organs, especially strong in the capitulum and could be obviously induced by various stress conditions. Promoters of ClPDH and ClProTs contained many cis-acting regulatory elements involved in stress responses and plant growth and development. High levels of free proline were found in flower buds, the capitulum under the non-stress condition and later periods of stress conditions except cold treatment. Interestingly, organ specificity and disparity also exist in the level of free proline under different stress conditions. Our study indicates that ClProTs play significant roles in proline accumulation and stress responses, and that ClProT2 could be used to genetically modify the stress resistance of chrysanthemums. In addition, proline metabolism might be closely related to plant flowering and floral development., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The dehydration-responsive element binding proteins (DREBs) are important transcription factors in the regulation of plant responses to abiotic stresses. In this study, BpDREB2, an AP2/DREB-type transcription factor gene, was cloned from a woody plant, Broussonetia papyrifera by RACE-PCR. Sequence analyses revealed that BpDREB2 protein has three characteristic domains, including an AP2/EREBP, a nuclear localization signal and an acidic activation domain. Yeast one-hybrid assays showed that BpDREB2 protein specifically binds to the DRE sequence and activates the expression of reporter genes in yeast. These results suggested that BpDREB2 protein could function as a transcription factor of DREB family. The expression of BpDREB2 gene was remarkably induced by dehydration and high-salt treatments, but no significant change was observed under ABA or low-temperature conditions. Importantly, transgenic expression of BpDREB2 gene in Arabidopsis significantly enhanced its tolerance to salt and freezing without causing growth retardation. Taken together, these results suggested that BpDREB2 is a novel member of the AP2/EREBP trans-acting factor family which could enhance salt stress tolerance of plants and has the potential application in the improvement of crops and economical tree species., (Copyright © 2013 Elsevier B.V. All rights reserved.)

ICE1 (inducer of CBF expression 1), a MYC-type bHLH transcription factor, is an important activator of CBF3/DREB1A for regulating cold signaling and stress tolerance. In this study, we isolated the novel ICE1-like gene SlICE1a from tomato which contains the conserved bHLH domain, an S-rich motif, and ACT-domain. It is localized in the nucleus and harbors transcription-activating activity in the N-terminal. In addition, the SlICE1a transcript is slightly upregulated by cold stress, salt stress, and osmotic stress. SlICE1a overexpression in tobacco enhances the induction of CBF/DREB and their target genes, consequently increasing the levels of proline, soluble sugars, and late embryogenesis abundant (LEA) proteins, and enhancing tolerance to cold stress, osmotic stress, and salt stress. SlICE1a functions in abiotic stress responses by regulating the expression of stress-tolerant genes, and is thus beneficial for crop improvement., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)