Cold Signaling Research Articles

Ion channels of cold transduction and transmission.

Thermosensation requires the activation of a unique collection of ion channels and receptors that work in concert to transmit thermal information. It is widely accepted that transient receptor potential melastatin 8 (TRPM8) activation is required for normal cold sensing; however, recent studies have illuminated major roles for other ion channels in this important somatic sensation. In addition to TRPM8, other TRP channels have been reported to contribute to cold transduction mechanisms in diverse sensory neuron populations, with both leak- and voltage-gated channels being identified for their role in the transmission of cold signals. Whether the same channels that contribute to physiological cold sensing also mediate noxious cold signaling remains unclear; however, recent work has found a conserved role for the kainite receptor, GluK2, in noxious cold sensing across species. Additionally, cold-sensing neurons likely engage in functional crosstalk with nociceptors to give rise to cold pain. This Review will provide an update on our understanding of the relationship between various ion channels in the transduction and transmission of cold and highlight areas where further investigation is required.

Environmental salinity differentiates responses to acute hypothermal stress in milkfish

Global warming has led to an increase in the frequency of cold extremes, causing significant economic losses in aquaculture, particularly in subtropical regions. Milkfish (Chanos chanos) holds significant importance in aquaculture within subtropical Asian regions. Despite milkfish's ability to tolerate varying salinity levels, frequent cold snaps associated with extreme weather events have caused substantial mortality. Understanding the molecular and cellular mechanisms underlying cold stress-induced cell death is crucial for developing effective strategies to mitigate such losses. Given the pivotal role of the liver in fish physiology, we established a primary milkfish hepatocyte culture demonstrating robust proliferation and expressing a unique marker leptin A. The molecular characterization of cold-treated hepatocytes at 18 °C showed that the mRNA levels of superoxide dismutase (sod1) and catalase (cat), responsible for neutralizing reactive oxygen species (ROS), were downregulated in freshwater (FW) conditions, while cat expression was upregulated in seawater (SW) conditions. This differential modulation of ROS signaling implies distinct responses in FW and SW, leading to higher ROS levels and increased cell death in FW condition compared to those in SW. Transcriptomic analysis of liver tissues from milkfish reared in FW or SW, with or without cold stress, revealed distinct gene expression patterns. Although cold stress affected a common set of genes in both FW and SW conditions, SW-specific cold responsive genes are associated with metabolic pathways while FW-specific genes were linked to cell proliferation pathways. Notably, gene set enrichment analysis highlighted the downregulation of cytochrome-related genes, a major source of ROS production, in response to cold stress in SW. In summary, our study unveils an insightful mechanism whereby the salinity of SW counteracts cold stress-induced ROS signaling, emphasizing the feasibility and practicality of preconditioning fish in SW as a preventive measure against cold stress-induced mortality.

Brassica rapa BrICE1 and BrICE2 Positively Regulate the Cold Tolerance via CBF and ROS Pathways, Balancing Growth and Defense in Transgenic Arabidopsis.

Winter rapeseed (Brassica rapa) has a good chilling and freezing tolerance. inducer of CBF expression 1 (ICE1) plays a crucial role in cold signaling in plants; however, its role in Brassica rapa remains unclear. In this study, we identified 41 ICE1 homologous genes from six widely cultivated Brassica species. These genes exhibited high conservation, with evolutionary complexity between diploid and allotetraploid species. Cold stress induced ICE1 homolog expression, with differences between strongly and weakly cold-tolerant varieties. Two novel ICE1 paralogs, BrICE1 and BrICE2, were cloned from Brassica rapa Longyou 6. Subcellular localization assays showed that they localized to the nucleus, and low temperature did not affect their nuclear localization. The overexpression of BrICE1 and BrICE2 increased cold tolerance in transgenic Arabidopsis and enhanced reactive oxygen species' (ROS) scavenging ability. Furthermore, our data demonstrate that overexpression of BrICE1 and BrICE2 inhibited root growth in Arabidopsis, and low temperatures could induce the degradation of BrICE1 and BrICE2 via the 26S-proteasome pathway. In summary, ICE1 homologous genes exhibit complex evolutionary relationships in Brassica species and are involved in the C-repeat/DREB binding factor (CBF) pathway and ROS scavenging mechanism in response to cold stress; these regulating mechanisms might also be responsible for balancing the development and cold defense of Brassica rapa.

A cold-inducible MYB like transcription factor, CsHHO2, positively regulates chilling tolerance of cucumber fruit by enhancing CsGR-RBP3 expression

Plant HRS1 (hypersensitive to low phosphate (Pi)-elicited primary root shortening 1) and its homologs have been primarily characterized in Pi and nitrogen responses. However, their regulatory roles in cold responses remain largely unexplored. Here, we characterized the functional roles of HRS1 homolog 2 (CsHHO2) in regulating cold resistance in harvested cucumber fruit and examined the dependency of the role on glycine-rich RNA-binding protein 3 (CsGR-RBP3) gene expression. Cold treatments strongly induced CsHHO2 expression in cucumber fruit. GUS staining and expression analysis revealed that cold treatment stimulated CsHHO2 expression, at least partially, by enhancing the promoter activity. Subcellular localization results indicated that the green fluorescent protein (GFP)-tagged CsHHO2 proteins were localized to both the nucleus and the cytoplasm (potentially the plasma membrane), with confirmed nuclear localization when co-overexpressed with mCherry. Reducing CsHHO2 expression in cucumber fruit through VIGS significantly compromised the chilling tolerance, while its overexpression in cucumber fruit and Arabidopsis plants enhanced cold tolerance. The results of electrophoretic mobility shift assay (EMSA), yeast one-hybrid (Y1H) assay and dual-luciferase reporter (DLR) assay indicated that CsHHO2 specifically bound to the promoter of CsGR-RBP3, and enhanced its transcription. Transcriptomic analysis indicated that most differentially expressed genes (DEGs) modulated by CsHHO2 and CsGR-RBP3 proteins were identical, and the common DEGs were mainly enriched in several stress defense pathways, such as plant-pathogen interaction, phenylpropanoid biosynthesis, and plant hormone signal transduction. Functional complementation analysis of CsHHO2 and CsGR-RBP3 in cucumber fruit revealed that CsGR-RBP3 expression were indispensable for CsHHO2-modulated cold resistance. These results collectively suggest that CsHHO2, activated by cold signals, positively regulates the chilling tolerance of cucumber fruit by enhancing CsGR-RBP3 expression. Overall, this work suggests CsHHO2 as a key regulator of cold tolerance in cucumber fruit, provides key genetic resources for breeding cold-resistant cucumbers, and sheds novel insight into the roles of HRS1 family members in regulating plant development under environmental stresses.

Transcriptomic analyses provide molecular insight into the cold stress response of cold-tolerant alfalfa

BackgroundDaye No.3 is a novel cultivar of alfalfa (Medicago sativa L.) that is well suited for cultivation in high-altitude regions such as the Qinghai‒Tibet Plateau owing to its high yield and notable cold resistance. However, the limited availability of transcriptomic information has hindered our investigation into the potential mechanisms of cold tolerance in this cultivar. Consequently, we conducted de novo transcriptome assembly to overcome this limitation. Subsequently, we compared the patterns of gene expression in Daye No. 3 during cold acclimatization and exposure to cold stress at various time points.ResultsA total of 15 alfalfa samples were included in the transcriptome assembly, resulting in 141.97 Gb of clean bases. A total of 441 DEGs were induced by cold acclimation, while 4525, 5016, and 8056 DEGs were identified at 12 h, 24 h, and 36 h after prolonged cold stress at 4 °C, respectively. The consistency between the RT‒qPCR and transcriptome data confirmed the accuracy and reliability of the transcriptomic data. KEGG enrichment analysis revealed that many genes related to photosynthesis were enriched under cold stress. STEM analysis demonstrated that genes involved in nitrogen metabolism and the TCA cycle were consistently upregulated under cold stress, while genes associated with photosynthesis, particularly antenna protein genes, were downregulated. PPI network analysis revealed that ubiquitination-related ribosomal proteins act as hub genes in response to cold stress. Additionally, the plant hormone signaling pathway was activated under cold stress, suggesting its vital role in the cold stress response of alfalfa.ConclusionsUbiquitination-related ribosomal proteins induced by cold acclimation play a crucial role in early cold signal transduction. As hub genes, these ubiquitination-related ribosomal proteins regulate a multitude of downstream genes in response to cold stress. The upregulation of genes related to nitrogen metabolism and the TCA cycle and the activation of the plant hormone signaling pathway contribute to the enhanced cold tolerance of alfalfa.

PHD17 acts as a target of miR1320 to negatively control cold tolerance via JA-activated signaling in rice

Plant Homeo Domain (PHD) proteins are involved in diverse biological processes during plant growth. However, the regulation of PHD genes on rice cold stress response remains largely unknown. Here, we reported that PHD17 negatively regulated cold tolerance in rice seedlings as a cleavage target of miR1320. PHD17 expression was greatly induced by cold stress, and was down-regulated by miR1320 overexpression and up-regulated by miR1320 knockdown. Through 5′RACE and dual luciferase assays, we found that miR1320 targeted and cleaved the 3′UTR region of PHD17. PHD17 was a nuclear-localized protein and acted as a transcriptional activator in yeast. PHD17 overexpression reduced cold tolerance of rice seedlings, while knockout of PHD17 increased cold tolerance, partially via the CBF cold signaling. By combining transcriptomic and physiological analyses, we demonstrated that PHD17 modulated ROS homeostasis and flavonoid accumulation under cold stress. K-means clustering analysis revealed that differentially expressed genes in PHD17 transgenic lines were significantly enriched in the jasmonic acid (JA) biosynthesis pathway, and expression of JA biosynthesis and signaling genes was verified to be affected by PHD17. Cold stress tests applied with MeJA or IBU (JA synthesis inhibitor) further suggested the involvement of PHD17 in JA-mediated cold signaling. Taken together, our results suggest that PHD17 acts downstream of miR1320 and negatively regulates cold tolerance of rice seedlings through JA-mediated signaling pathway.

CIPK11 phosphorylates GSTU23 to promote cold tolerance in Camellia sinensis.

Cold stress negatively impacts the growth, development, and quality of Camellia sinensis (Cs, tea) plants. CBL-interacting protein kinases (CIPK) comprise a pivotal protein family involved in plant development and response to multiple environmental stimuli. However, their roles and regulatory mechanisms in tea plants (Camellia sinensis (L.) O. Kuntze) remain unknown. Here we show that CsCBL-interacting protein kinase 11 (CsCIPK11), whose transcript abundance was significantly induced at low temperatures, interacts and phosphorylates tau class glutathione S-transferase 23 (CsGSTU23). CsGSTU23 was also a cold-inducible gene and has significantly higher transcript abundance in cold-resistant accessions than in cold-susceptible accessions. CsCIPK11 phosphorylated CsGSTU23 at Ser37, enhancing its stability and enzymatic activity. Overexpression of CsCIPK11 in Arabidopsis thaliana resulted in enhanced cold tolerance under freezing conditions, while transient knockdown of CsCIPK11 expression in tea plants had the opposite effect, resulting in decreased cold tolerance and suppression of the C-repeat-binding transcription factor (CBF) transcriptional pathway under freezing stress. Furthermore, the transient overexpression of CsGSTU23 in tea plants increased cold tolerance. These findings demonstrate that CsCIPK11 plays a central role in the signaling pathway to cold signals and modulates antioxidant capacity by phosphorylating CsGSTU23, leading to improved cold tolerance in tea plants.

Regulatory Networks Underlying Plant Responses and Adaptation to Cold Stress.

Cold is a key determinant for plant growth and flowering time as well as an important environmental factor limiting plant growth and development. Recent studies have revealed the complex regulatory networks associated with plant responses to cold and identified their interconnections with signaling pathways related to light, the circadian clock, plant hormones, and pathogen defense. In this article, we review recent advances in understanding the molecular basis of cold perception and signal transduction pathways. We also summarize recent developments in the study of cold-responsive growth and flowering. Finally, we propose future directions for the study of long-term cold sensing, RNA secondary structures in response to cold, and the development of cold-tolerant and high-yield crops.

The transcription factor ERF110 promotes cold tolerance by directly regulating sugar and sterol biosynthesis in citrus.

ERFs (ethylene-responsive factors) are known to play a key role in orchestrating cold stress signal transduction. However, the regulatory mechanisms and target genes of most ERFs are far from being well deciphered. In this study, we identified a cold-induced ERF, designated as PtrERF110, from trifoliate orange (Poncirus trifoliata L. Raf., also known as Citrus trifoliata L.), an elite cold-hardy plant. PtrERF110 is a nuclear protein with transcriptional activation activity. Overexpression of PtrERF110 remarkably enhanced cold tolerance in lemon (Citrus limon) and tobacco (Nicotiana tabacum), whereas VIGS (virus-induced gene silencing)-mediated knockdown of PtrERF110 drastically impaired the cold tolerance. RNA sequence analysis revealed that PtrERF110 overexpression resulted in global transcriptional reprogramming of a range of stress-responsive genes. Three of the genes, including PtrERD6L16 (early responsive dehydration 6-like transporters), PtrSPS4 (sucrose phosphate synthase 4), and PtrUGT80B1 (UDP-glucose: sterol glycosyltransferases 80B1), were confirmed as direct targets of PtrERF110. Consistently, PtrERF110-overexpressing plants exhibited higher levels of sugars and sterols compared to their wild type counterparts, whereas the VIGS plants had an opposite trend. Exogenous supply of sucrose restored the cold tolerance of PtrERF110-silencing plants. In addition, knockdown of PtrSPS4, PtrERD6L16, and PtrUGT80B1 substantially impaired the cold tolerance of P. trifoliata. Taken together, our findings indicate that PtrERF110 positively modulates cold tolerance by directly regulating sugar and sterol synthesis through transcriptionally activating PtrERD6L16, PtrSPS4, and PtrUGT80B1. The regulatory modules (ERF110-ERD6L16/SPS4/UGT80B1) unraveled in this study advance our understanding of the molecular mechanisms underlying sugar and sterol accumulation in plants subjected to cold stress.

Multimodal Imaging, Including Laser Speckle Flowgraphy: A Case of Retinal Metastasis.

Intraocular metastases of systemic cancer are most frequently located in the choroid, followed by the iris and ciliary body, while retinal metastases are extremely rare. Here we present a case of retinal metastasis and analyze multimodal imaging. A 66-year-old woman with a medical history of breast cancer 5 years earlier was referred to our Department struggling with blurry vision in her right eye. At initial examination, her best-corrected visual acuity (BCVA) was 1.0 oculus dexter (OD). Fundus examination revealed a yellowish elevated lesion with irregular surface, measuring 2 papillary diameters, along with serous retinal detachment (SRD) on the temporal side of the optic disc. Optical coherence tomography showed SRD with an isointense nodule extending across all retinal layers. Fluorescein angiography showed hyperfluorescence and vigorous fluorescence leakage inside the tumor in the early and late phases, respectively. Indocyanine green angiography depicted feeder and drainage vessels within the mass. Laser speckle flowgraphy (LSFG) showed a cold signal inside the tumor. Based on these clinical findings, the mass was diagnosed as a retinal metastasis. Eight days after the initial visit, the patient underwent external beam radiation to the right eye. One month after the initial diagnosis, her BCVA was 0.7 OD, the tumor was localized, and SRD had decreased. LSFG indicated vascular remodeling with marginally warmer signals in the tumor. LSFG of the retinal metastasis showed a cold signal, suggesting low tumor blood flow velocity and that the tumor may have grown slowly. LSFG findings are likely to play a supportive role in clinical diagnosis and contribute to better understanding of pathogenesis in juxtapapillary tumors.

Multiomics comprehensive analysis of pre-storage low-temperature on cowpea metabolism

The purpose of this study is to investigate the effect of low temperature on the storage quality of cowpea and explore its regulatory mechanism. In this study, we performed transcriptome, metabolome, and chromatin accessibility analyses of pericarp tissues of cowpeas stored at 20 °C with and without exposure to 4 °C for 2 d. The results showed that low temperature induced the expression of genes related to membrane lipid metabolism (PLC, PLA1, LOXs), cell wall metabolism (PG, β-glu), and antioxidant pathways (POD, PPO, SOD). Lipid metabolites such as 9-oxo-10E,12Z-octadecadienoic acid, 9-hydroperoxy-10E,12,15Z-octadecatrienoic acid, 13S-hydroperoxy-9Z,11E-octadecadienoic acid, and flavonoid metabolites such as liquiritigenin, daidzein, glyceollin III accumulated under low-temperature treatment. Low-temperature treatment also affected cold perception mechanisms and cell signal transduction, altering the expression of genes related to calcium signaling (CPK, CML), the MAPK cascade pathway (MPKKK17/18, MKS1, AMPK), and the ICE-CBF-COR pathway (CBF1, ICE1). Low-temperature treatment impacted transcription factors of the AP2/ERF, MYB, NAC, WRKY, and LOB families. These findings suggest that pre-storage at low temperatures induced the expression of genes involved in membrane lipid metabolism, cell wall metabolism, antioxidant pathways, cold signal transduction pathways, and corresponding transcription factors and their target genes. Treatment effects on genes and metabolites may be associated with chilling injury of cowpeas.

Differential phosphorylation of Ca2+-permeable channel CYCLIC NUCLEOTIDE-GATED CHANNEL20 modulates calcium-mediated freezing tolerance in Arabidopsis.

Plants respond to cold stress at multiple levels, including increasing cytosolic calcium (Ca2+) influx and triggering the expression of cold-responsive genes. In this study, we show that the Ca2+-permeable channel CYCLIC NUCLEOTIDE-GATED CHANNEL20 (CNGC20) positively regulates freezing tolerance in Arabidopsis (Arabidopsis thaliana) by mediating cold-induced Ca2+ influx. Moreover, we demonstrate that the leucine-rich repeat receptor-like kinase PLANT PEPTIDE CONTAINING SULFATED TYROSINE1 RECEPTOR (PSY1R) is activated by cold, phosphorylating and enhancing the activity of CNGC20. The psy1r mutant exhibits decreased cold-evoked Ca2+ influx and freezing tolerance. Conversely, COLD-RESPONSIVE PROTEIN KINASE1 (CRPK1), a protein kinase that negatively regulates cold signaling, phosphorylates and facilitates the degradation of CNGC20 under prolonged periods of cold treatment, thereby attenuating freezing tolerance. This study thus identifies PSY1R and CRPK1 kinases that regulate CNGC20 activity and stability, respectively, thereby antagonistically modulating freezing tolerance in plants.

INDUCER OF CBF EXPRESSION 1 promotes cold-enhanced immunity by directly activating salicylic acid signaling.

Cold stress affects plant immune responses, and this process may involve the salicylic acid (SA) signaling pathway. However, the underlying mechanism by which low-temperature signals coordinate with SA signaling to regulate plant immunity remains unclear. Here, we found that low temperatures enhanced the disease resistance of Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000. This process required INDUCER OF CBF EXPRESSION 1 (ICE1), the core transcription factor in cold-signal cascades. ICE1 physically interacted with NONEXPRESSER OF PATHOGENESIS-RELATED GENES 1 (NPR1), the master regulator of the SA signaling pathway. Enrichment of ICE1 on the PATHOGENESIS-RELATED GENE 1 (PR1) promoter and its ability to transcriptionally activate PR1 were enhanced by NPR1. Further analyses revealed that cold stress signals cooperate with SA signals to facilitate plant immunity against pathogen attack in an ICE1-dependent manner. Cold treatment promoted interactions of NPR1 and TGACG-BINDING FACTOR 3 (TGA3) with ICE1 and increased the ability of the ICE1-TGA3 complex to transcriptionally activate PR1. Together, our results characterize a critical role of ICE1 as an indispensable regulatory node linking low-temperature-activated and SA-regulated immunity. Understanding this crucial role of ICE1 in coordinating multiple signals associated with immunity broadens our understanding of plant-pathogen interactions.

Histone deacetylase OsHDA716 represses rice chilling tolerance by deacetylating OsbZIP46 to reduce its transactivation function and protein stability.

Low temperature is a major environmental factor limiting plant growth and crop production. Epigenetic regulation of gene expression is important for plant adaptation to environmental changes, whereas the epigenetic mechanism of cold signaling in rice (Oryza sativa) remains largely elusive. Here, we report that the histone deacetylase (HDAC) OsHDA716 represses rice cold tolerance by interacting with and deacetylating the transcription factor OsbZIP46. The loss-of-function mutants of OsHDA716 exhibit enhanced chilling tolerance, compared with the wild-type plants, while OsHDA716 overexpression plants show chilling hypersensitivity. On the contrary, OsbZIP46 confers chilling tolerance in rice through transcriptionally activating OsDREB1A and COLD1 to regulate cold-induced calcium influx and cytoplasmic calcium elevation. Mechanistic investigation showed that OsHDA716-mediated OsbZIP46 deacetylation in the DNA-binding domain reduces the DNA-binding ability and transcriptional activity as well as decreasing OsbZIP46 protein stability. Genetic evidence indicated that OsbZIP46 deacetylation mediated by OsHDA716 reduces rice chilling tolerance. Collectively, these findings reveal that the functional interplay between the chromatin regulator and transcription factor fine-tunes the cold response in plant and uncover a mechanism by which HDACs repress gene transcription through deacetylating nonhistone proteins and regulating their biochemical functions.

The Roles of Circadian Clock Genes in Plant Temperature Stress Responses.

Plants monitor day length and memorize changes in temperature signals throughout the day, creating circadian rhythms that support the timely control of physiological and metabolic processes. The DEHYDRATION-RESPONSE ELEMENT-BINDING PROTEIN 1/C-REPEAT BINDING FACTOR (DREB1/CBF) transcription factors are known as master regulators for the acquisition of cold stress tolerance, whereas PHYTOCHROME INTERACTING FACTOR 4 (PIF4) is involved in plant adaptation to heat stress through thermomorphogenesis. Recent studies have shown that circadian clock genes control plant responses to temperature. Temperature-responsive transcriptomes show a diurnal cycle and peak expression levels at specific times of throughout the day. Circadian clock genes play essential roles in allowing plants to maintain homeostasis by accommodating temperature changes within the normal temperature range or by altering protein properties and morphogenesis at the cellular level for plant survival and growth under temperature stress conditions. Recent studies revealed that the central oscillator genes CIRCADIAN CLOCK ASSOCIATED 1/LATE ELONGATED HYPOCOTYL (CCA1/LHY) and PSEUDO-RESPONSE REGULATOR5/7/9 (PRR5/7/9), as well as the EVENING COMPLEX (EC) genes REVEILLE4/REVEILLE8 (REV4/REV8), were involved in the DREB1 pathway of the cold signaling transcription factor and regulated the thermomorphogenesis gene PIF4. Further studies showed that another central oscillator, TIMING OF CAB EXPRESSION 1 (TOC1), and the regulatory protein ZEITLUPE (ZTL) are also involved. These studies led to attempts to utilize circadian clock genes for the acquisition of temperature-stress resistance in crops. In this review, we highlight circadian rhythm regulation and the clock genes involved in plant responses to temperature changes, as well as strategies for plant survival in a rapidly changing global climate.

The Diverse Impacts of El Niño on Northeastern Canada and Greenland Surface Air Temperatures

Abstract El Niño is known to affect Arctic temperature. However, the robustness of the observed relationship between El Niño and Arctic temperature remains debated. Here we reexamine the impacts of El Niño on the Arctic temperature in boreal winter [December–February (DJF)] using reanalysis datasets and atmospheric model experiments. This study shows that extreme El Niño events are accompanied by significant boreal winter cooling over northeastern Canada and Greenland (NECG), while moderate eastern Pacific (MEP) El Niño events are accompanied by significant boreal winter warming in this region. For central Pacific (CP) El Niño events, a cold signal appears in NECG, but with no statistical significance. During extreme El Niño winters, a positive Pacific–North America (PNA)-like pattern is seen in the Pacific, and anomalously negative 200-hPa geopotential height (Z200) strengthening occurs over NECG, which is a response to anomalous strong wave activity originating in the tropical Pacific. El Niño–induced circulation anomalies can further induce NECG cooling via cold temperature advection and decreased downward longwave radiation. In contrast, for the MEP El Niño, the subtropical jet extends zonally from the North Pacific to the North Atlantic, which is accompanied by increased baroclinicity anomalies and favors the propagation of synoptic eddies into the Atlantic, leading to a negative North Atlantic Oscillation (NAO)-like pattern. This in turn could further enhance the positive Z200 anomalies over NECG, resulting in anomalous warming in NECG through warm temperature advection and enhanced downward longwave radiation. A series of atmospheric model experiments simulates the observed circulation changes and associated warming over NECG. Significance Statement This work investigates the different impacts of the three El Niño types on regional Arctic wintertime temperature anomalies based on observations and model experiments. The impacts of El Niño events on northeastern Canada and Greenland temperatures during boreal winter show distinct differences between extreme El Niño and moderate EP El Niño events. These distinct differences can be attributed to the different atmospheric circulation patterns induced by different SST patterns, which can lead to warm (cold) temperature advection and enhanced (decreased) downward longwave radiation. These results highlight the different impacts of extreme and moderate EP El Niños on Arctic temperatures and provide an improved understanding of the impact of El Niños on the Arctic climate.

Exogenous Melatonin Promotes Cold Tolerance in Grape Seedlings: Physiological, Transcriptomic, and Functional Evidence.

Melatonin (MEL) is an antioxidant molecule that enhances plant tolerance to environmental stress. However, the mechanisms by which MEL regulates cold signaling pathways in grapes under cold stress remain elusive. Here, we investigated the physiological and transcriptomic changes in grape seedlings treated with exogenous MEL to determine their protective role under cold stress. Results showed that 150 μM MEL effectively attenuated cold-induced cell damage by reducing reactive oxygen species (ROS) and preserving the chloroplast structure and function. MEL also inhibited tannin degradation, which contributed to its protective effect. Exogenous MEL promoted the synthesis of endogenous MEL, abscisic acid, auxin, and cytokinin while inhibiting gibberellin. Transcriptomic profiling revealed 776 differentially expressed transcripts in MEL-treated samples compared to controls. Functional analysis of a candidate hub gene, VvHSFA6b, showed that its overexpression in grape calli enhances cold tolerance by activating jasmonic acid synthesis pathway genes, promoting JA accumulation, and inhibiting JAZ-repressed transcription factors.

Decoding VaCOLD1 Function in Grapevines: A Membrane Protein Enhancing Cold Stress Tolerance.

In globally cultivated grapevines, low-temperature stress poses a persistent challenge. Although COLD1 is recognized as a cold receptor in rice, its function in grapevine cold signaling is unclear. Here, we identified VaCOLD1, a transmembrane protein from the cold-tolerant Vitis amurensis Rupr, which is primarily located on plasma and endoplasmic reticulum membranes. Broadly expressed across multiple tissues, VaCOLD1 responds to various environmental stresses, particularly to cold. Its promoter contains distinct hormone- and stress-responsive elements, with GUS assays confirming widespread expression in Arabidopsis thaliana. Validation of interaction between VaCOLD1 and VaGPA1, together with their combined expression in yeast and grape calli, notably improved cold endurance. Overexpression of VaCOLD1 enhances cold tolerance in Arabidopsis by strengthening the CBF-COR signaling pathway. This is achieved through shielding against osmotic disturbances and modifying the expression of ABA-mediated genes. These findings emphasize the critical role of the VaCOLD1-VaGPA1 complex in mediating the response to cold stress via the CBF-COR pathway.

Advances and opportunities in unraveling cold-tolerance mechanisms in the world's primary staple food crops.

Temperatures below or above optimal growth conditions are among the major stressors affecting productivity, end-use quality, and distribution of key staple crops including rice (Oryza sativa), wheat (Triticum aestivum), and maize (Zea mays L.). Among temperature stresses, cold stress induces cellular changes that cause oxidative stress and slowdown metabolism, limit growth, and ultimately reduce crop productivity. Perception of cold stress by plant cells leads to the activation of cold-responsive transcription factors and downstream genes, which ultimately impart cold tolerance. The response triggered in crops to cold stress includes gene expression/suppression, the accumulation of sugars upon chilling, and signaling molecules, among others. Much of the information on the effects of cold stress on perception, signal transduction, gene expression, and plant metabolism are available in the model plant Arabidopsis but somewhat lacking in major crops. Hence, a complete understanding of the molecular mechanisms by which staple crops respond to cold stress remain largely unknown. Here, we make an effort to elaborate on the molecular mechanisms employed in response to low-temperature stress. We summarize the effects of cold stress on the growth and development of these crops, the mechanism of cold perception, and the role of various sensors and transducers in cold signaling. We discuss the progress in cold tolerance research at the genome, transcriptome, proteome, and metabolome levels and highlight how these findings provide opportunities for designing cold-tolerant crops for the future.

HbBIN2 Functions in Plant Cold Stress Resistance through Modulation of HbICE1 Transcriptional Activity and ROS Homeostasis in Hevea brasiliensis.

Cold stress poses significant limitations on the growth, latex yield, and ecological distribution of rubber trees (Hevea brasiliensis). The GSK3-like kinase plays a significant role in helping plants adapt to different biotic and abiotic stresses. However, the functions of GSK3-like kinase BR-INSENSITIVE 2 (BIN2) in Hevea brasiliensis remain elusive. Here, we identified HbBIN2s of Hevea brasiliensis and deciphered their roles in cold stress resistance. The transcript levels of HbBIN2s are upregulated by cold stress. In addition, HbBIN2s are present in both the nucleus and cytoplasm and have the ability to interact with the INDUCER OF CBF EXPRESSION1(HbICE1) transcription factor, a central component in cold signaling. HbBIN2 overexpression in Arabidopsis displays decreased tolerance to chilling stress with a lower survival rate and proline content but a higher level of electrolyte leakage (EL) and malondialdehyde (MDA) than wild type under cold stress. Meanwhile, HbBIN2 transgenic Arabidopsis treated with cold stress exhibits a significant increase in the accumulation of reactive oxygen species (ROS) and a decrease in the activity of antioxidant enzymes. Further investigation reveals that HbBIN2 inhibits the transcriptional activity of HbICE1, thereby attenuating the expression of C-REPEAT BINDING FACTOR (HbCBF1). Consistent with this, overexpression of HbBIN2 represses the expression of CBF pathway cold-regulated genes under cold stress. In conclusion, our findings indicate that HbBIN2 functions as a suppressor of cold stress resistance by modulating HbICE1 transcriptional activity and ROS homeostasis.