The transcription factor VaMYC2 from Chinese wild Vitis amurensis enhances cold tolerance of grape (V. vinifera) by up-regulating VaCBF1 and VaP5CS

Role of jasmonates in plant response to temperature stress

The ambient temperature exerts a significant influence on the growth and development of plants, which are sessile organisms. Exposure to extreme temperatures, both low and high, has a detrimental impact on plant growth and development, crop yields, and even geographical distribution. Jasmonates constitute a class of lipid hormones that regulate plant tolerance to biotic and abiotic stresses. Recent studies have revealed that jasmonate biosynthesis and signaling pathways are integral to plant responses to both high and low temperatures. Exogenous application of jasmonate improves cold and heat tolerance in plants and reduces cold injury in fruits and vegetables during cold storage. Jasmonate interacts with low and high temperature key response factors and engages in crosstalk with primary and secondary metabolic pathways, including hormones, under conditions of temperature stress. This review presents a comprehensive summary of the jasmonate synthesis and signal transduction pathway, as well as an overview of the functions and mechanisms of jasmonate in response to temperature stress.

PpERF17 alleviates peach fruit postharvest chilling injury under elevated CO2 by activating jasmonic acid and γ-aminobutyric acid biosynthesis

Internal browning (IB) is a common chilling injury (CI) feature in peach fruit after prolonged cold storage. Our previous study demonstrated that low O2 and elevated CO2 (eCO2) condition of modified atmosphere (MA) storage alleviated CI by facilitating the accumulation of jasmonic acids (JAs) and γ-aminobutyric acid (GABA) in 'Zhonghuashoutao' ('ZHST') peach fruit. Here we show that 10% CO2 alone can improve cold tolerance, with ethylene response factor 17 (PpERF17) identified as a pivotal transcription factor (TF) that promotes biosynthesis of JAs and GABA. Stable transformation of PpERF17 in tobacco resulted in reduced cold damage, attributed to decreased levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA), as well as enhanced accumulation of JAs and GABA. Moreover, under eCO2, PpMYC2.1, the master regulator of JA signaling, was found to activate transcription of 13S-lipoxygenase (Pp13S-LOX), allene oxide synthase (PpAOS), 12-oxophytodienoate reductase 3 (PpOPR3), and glutamate decarboxylase (PpGAD), while also inducing the expression of the upstream TF PpERF17, thereby establishing positive feedback loops upregulating JA and GABA biosynthesis. Finally, application of methyl jasmonate (MeJA) to fruit before shelf transfer from cold storage alleviated chilling injury development, due to increased accumulation of JAs and GABA as a result of raised expression of related biosynthetic genes. Collectively, our results suggest that eCO2-induced PpERF17 enhances JAs and GABA accumulation while activating the JA signaling pathway. This contributes to a positive feedback loop mediated by PpMYC2.1, ultimately alleviating CI of peach fruit through the sustained accumulation of JAs and GABA.

Molecular mechanism of response to low-temperature during the natural overwintering period of Rosa persica

KEY MESSAGE

The JA and ICE-CBF-COR signaling pathways play important roles in the low-temperature response of Rosa persica, with RpMYC2 interacting with multiple transcription factors and positively regulating tolerance to low-temperature stress. Rosa persica is highly resilient to cold and drought, making it a valuable resource for breeding in the Rosa. However, the response mechanism of R. persica during the overwintering period remains unclear. This study examined root and stem tissues of R. persica over an eight-month natural open field overwintering period, measuring physiological indices of cold tolerance and investigating changes in cold tolerance across different overwintering stages. The values of physiological indicators of cold hardiness of R. persica roots and stems increased and then decreased. Osmoregulatory substances were the primary contributors to cold hardiness of R. persica roots, while antioxidant enzyme systems played a dominant role in cold hardiness of stems. Differential gene enrichment analyses revealed that oxidative reactions, the synthesis of various secondary metabolites, and hormone signaling pathways are crucial in establishing cold tolerance of R. persica at different overwintering stages. Weighted gene co-expression network and time-ordered gene co-expression network analyses identified the gene RpMYC2 as potentially key to cold tolerance in R. persica. Yeast two-hybrid discovery revealed that RpMYC2 interacts with multiple transcription factors to regulate cold stress resistance in R. persica. Based on the transcriptome, key genes involved in response to low temperature were identified in this study, providing the physiological and molecular insights for cold tolerance breeding of Rosa.

Genome-Wide Identification and Expression Divergence of CBF Family in Actinidia arguta and Functional Analysis of AaCBF4 Under Cold Stress

The C-repeat binding factors (CBFs) gene is essential for plants' cold response, which could not only be induced by the inducer of CBF expression (ICE) genes but also activated the expression of the cold-regulated (COR) gene, thereby participating in the ICE-CBF-COR cold response pathway. However, this gene family and its functions in Actinidia arguta remain unclear. In this study, whole-genome identification and functional analysis of CBF family members in A. arguta were performed. Eighteen CBF genes, which were located on four chromosomes and had five tandem repeats, were identified. The proteins encoded by the genes were predicted to be located in the nucleus and cytoplasm. The results of the promoter cis-acting element analysis revealed light response elements, low-temperature response elements, and hormone (methyl jasmonate, gibberellin, salicylic acid, etc.) response elements. We analyzed collinearity with other kiwifruit genomes, and, interestingly, the number of CBF family members differed across geographic locations of A. arguta. RT-qPCR revealed that the expression of the CBF gene family differed under low-temperature treatment; specifically, we observed differences in the expression of all the genes. Based on phylogenetic relationships and RT-qPCR analysis, the expression of AaCBF4.1 (AaCBF4) was found to be highly upregulated, and the function of this gene in cold resistance was further verified via overexpression in transgenic Arabidopsis. AaCBF4-overexpressing plants showed higher tolerance to cold stress, showing a higher germination rate, higher chlorophyll content and lower relative electrolyte leakage. In addition, compared with the wild-type Arabidopsis, the overexpressing plants exhibited significantly reduced oxidative damage due to the reduction in reactive oxygen species production under cold stress. Therefore, AaCBF4 plays an important role in improving the cold resistance of Actinidia arguta and can be further used to develop kiwifruit germplasm resources with strong cold resistance.

Understanding cold stress response mechanisms in plants: an overview

Low-temperature stress significantly impacts plant growth, development, yield, and geographical distribution. However, during the long-term process of evolution, plants have evolved complicated mechanisms to resist low-temperature stress. The cold tolerance trait is regulated by multiple pathways, such as the Ca2+ signaling cascade, mitogen-activated protein kinase (MAPK) cascade, inducer of CBF expression 1 (ICE1)-C-repeat binding factor (CBF)-cold-reulated gene (COR) transcriptional cascade, reactive oxygen species (ROS) homeostasis regulation, and plant hormone signaling. However, the specific responses of these pathways to cold stress and their interactions are not fully understood. This review summarizes the response mechanisms of plants to cold stress from four aspects, including cold signal perception and transduction, ICE1-CBF-COR transcription cascade regulation, ROS homeostasis regulation and plant hormone signal regulation. It also elucidates the mechanism of cold stress perception and Ca2+ signal transduction in plants, and proposes the important roles of transcription factors (TFs), post-translational modifications (PTMs), light signals, circadian clock factors, and interaction proteins in the ICE1-CBF-COR transcription cascade. Additionally, we analyze the importance of ROS homeostasis and plant hormone signaling pathways in plant cold stress response, and explore the cross interconnections among the ICE1-CBF-COR cascade, ROS homeostasis, and plant hormone signaling. This comprehensive review enhances our understanding of the mechanism of plant cold tolerance and provides a molecular basis for genetic strategies to improve plant cold tolerance.

Transcriptome and metabolome atlas reveals contributions of sphingosine and chlorogenic acid to cold tolerance in Citrus

Citrus is one of the most important fruit crop genera in the world, but many Citrus species are vulnerable to cold stress. Ichang papeda (Citrus ichangensis), a cold-hardy citrus species, holds great potential for identifying valuable metabolites that are critical for cold tolerance in Citrus. However, the metabolic changes and underlying mechanisms that regulate Ichang papeda cold tolerance remain largely unknown. In this study, we compared the metabolomes and transcriptomes of Ichang papeda and HB pummelo (Citrus grandis "Hirado Buntan", a cold-sensitive species) to explore the critical metabolites and genes responsible for cold tolerance. Metabolomic analyses led to the identification of common and genotype-specific metabolites, consistent with transcriptomic alterations. Compared to HB pummelo under cold stress, Ichang papeda accumulated more sugars, flavonoids, and unsaturated fatty acids, which are well-characterized metabolites involved in stress responses. Interestingly, sphingosine and chlorogenic acid substantially accumulated only in Ichang papeda. Knockdown of CiSPT (C. ichangensis serine palmitoyltransferase) and CiHCT2 (C. ichangensis hydroxycinnamoyl-CoA: shikimate hydroxycinnamoyltransferase2), two genes involved in sphingosine and chlorogenic acid biosynthesis, dramatically decreased endogenous sphingosine and chlorogenic acid levels, respectively. This reduction in sphingosine and chlorogenic acid notably compromised the cold tolerance of Ichang papeda, whereas exogenous application of these metabolites increased plant cold tolerance. Taken together, our findings indicate that greater accumulation of a spectrum of metabolites, particularly sphingosine and chlorogenic acid, promotes cold tolerance in cold-tolerant citrus species. These findings broaden our understanding of plant metabolic alterations in response to cold stress and provide valuable targets that can be manipulated to improve Citrus cold tolerance.

Evolution of PIN gene family between monocotyledons and dicotyledons and VvPIN1 negatively regulates freezing tolerance in transgenic Arabidopsis

The PIN-FORMED (PIN) proteins mediate the auxin flow throughout the plant and have been identified in many species. However, evolution differences in the PIN gene families have not been systematically analyzed, and their functions under abiotic stresses in grape are largely unexplored. In this study, 373 PIN genes were identified from 25 species and divided into 3 subgroups. Physicochemical properties analysis indicated that most of the PIN proteins were unstable alkaline hydrophobic proteins in nature. The synteny analysis showed that the PINs contained strong gene duplication. Motif composition revealed that PIN gene sequence differences between monocotyledons and dicotyledons were due to evolutionary-induced base loss, and the loss was more common in dicotyledonous. Meanwhile, the codon usage bias showed that the PINs showed stronger codon preference in monocotyledons, monocotyledons biased towards C3s and G3s, and dicotyledons biased towards A3s and T3s. In addition, the VvPIN1 can interact with VvCSN5. Significantly, under freezing treatment, the ion leakage,O 2 · - $$ \left({O}_2^{\cdotp -}\right) $$ , H2O2, and malondialdehyde (MDA) were obviously increased, while the proline (Pro) content, peroxidase (POD) activity, and glutathione (GSH) content were decreased in VvPIN1-overexpressing Arabidopsis compared to the wild type (WT). And quantitative real-time PCR (qRT-PCR) showed that AtICE1, AtICE2, AtCBF1, AtCBF2, and AtCBF3 were down-regulated in overexpression lines. These results demonstrated that VvPIN1 negatively regulated the freezing tolerance in transgenic Arabidopsis. Collectively, this study provides a novel insight into the evolution and a basis for further studies on the biological functions of PIN genes in monocotyledons and dicotyledons.

Integrated anatomical structure, physiological, and transcriptomic analyses to identify differential cold tolerance responses of Ziziphus jujuba mill. 'Yueguang' and its autotetraploid 'Hongguang'

Cold stress is a limiting stress factor that limits plant distribution and development; however, polyploid plants have specific characteristics such as higher resistance to abiotic stress, especially cold stress, that allow them to overcome this challenge. The cultivated cultivar Ziziphus jujuba Mill. 'Yueguang' (YG) and its autotetraploid counterpart 'Hongguang' (HG) exhibit differential cold tolerance. However, the underlying molecular mechanism and methods to enhance their cold tolerance remain unknown. Anatomical structure and physiological analysis indicated YG had a higher wood bark ratio, and xylem ratio under cold treatment compared to HG. However, the half-lethal temperature (LT50), cortex ratio, and malondialdehyde (MDA) content were significantly decreased in YG than HG, which indicated YG was cold tolerant than HG. Transcriptome analysis showed that 2084, 1725, 2888, and 2934 differentially expressed genes (DEGs) were identified in HC vs YC, H20 vs Y20, Y20 vs YC, and H20 vs HC treatment, respectively. Meanwhile, KEGG enrichment analysis of DEGs showed that several metabolic pathways, primarily plant hormone signal transduction and the MAPK signaling pathway, were involved in the differential regulation of cold tolerance between YG and HG. Furthermore, exogenous abscisic acid (ABA) and brassinolide (BR) treatments could improve their cold tolerance through increased SOD and POD activities, decreased relative electrical conductivity, and MDA content. All of these findings suggested that plant hormone signal transduction, particularly ABA and BR, might have an important role in the regulation of differential cold tolerance between YG and HG, laying the foundation for further improving cold tolerance in jujube and examining the molecular mechanisms underlying differences in cold tolerance among different ploidy cultivars.

Overexpression of VaBAM3 from Vitis amurensis enhances seedling cold tolerance by promoting soluble sugar accumulation and reactive oxygen scavenging

KEY MESSAGE

The VaBAM3 cloned from Vitis amurensis can enhance the cold tolerance of overexpressed plants, but VaBAM3 knock out by CRISPR/Cas9 system weakened grape callus cold tolerance. In grape production, extreme cold conditions can seriously threaten plant survival and fruit quality. Regulation of starch content by β-amylase (BAM, EC: 3.2.1.2) contributes to cold tolerance in plants. In this study, we cloned the VaBAM3 gene from an extremely cold-tolerant grape, Vitis amurensis, and overexpressed it in tomato and Arabidopsis plants, as well as in grape callus for functional characterization. After exposure to cold stress, leaf wilting in the VaBAM3-overexpressing tomato plants was slightly less pronounced than that in wild-type tomato plants, and these plants were characterized by a significant accumulation of autophagosomes. Additionally, the VaBAM3-overexpressing Arabidopsis plants had a higher freezing tolerance than the wild-type counterparts. Under cold stress conditions, the activities of total amylase, BAM, peroxidase, superoxide dismutase, and catalase in VaBAM3-overexpressing plants were significantly higher than those in the corresponding wild-type plants. Furthermore, sucrose, glucose, and fructose contents in these lines were similarly significantly higher, whereas starch contents were reduced in comparison to the levels in the wild-type plants. Furthermore, we detected high CBF and COR gene expression levels in cold-stressed VaBAM3-overexpressing plants. Compared with those in VaBAM3-overexpressing grape callus, the aforementioned indicators tended to change in the opposite direction in grape callus with silenced VaBAM3. Collectively, our findings indicate that heterologous overexpression of VaBAM3 enhanced cold tolerance of plants by promoting the accumulation of soluble sugars and scavenging of excessive reactive oxygen species. These findings provide a theoretical basis for the cultivation of cold-resistant grape and support creation of germplasm resources for this purpose.

VvERF117 positively regulates grape cold tolerance through direct regulation of the antioxidative gene BAS1

Cold stress significantly threatens grape quality, yield, and geographical distribution. Although ethylene-responsive factors (ERFs) are recognized for their pivotal roles in cold stress, the regulatory mechanisms of many ERFs contributing to tolerance remain unclear. In this study, we identified the cold-responsive gene VvERF117 and elucidated its positive regulatory function in cold tolerance. VvERF117 exhibits transcriptional activity and localizes to the nucleus. VvERF117 overexpression improved cold tolerance in transgenic Arabidopsis, grape calli, and grape leaves, whereas VvERF117 silencing increased cold sensitivity in grape calli and leaves. Furthermore, VvERF117 overexpression remarkably upregulated the expression of several stress-related genes. Importantly, BAS1, encoding a 2-Cys peroxidase (POD), was confirmed as a direct target gene of VvERF117. Meanwhile, compared to the wild-type, POD activity and H2O2 content were remarkably increased and decreased in VvERF117-overexpressing grape calli and leaves, respectively. Conversely, VvERF117 silencing displayed the opposite trend in grape calli and leaves under cold stress. These findings indicate that VvERF117 plays a positive role in cold resistance by, at least in part, enhancing antioxidant capacity through regulating the POD-encoding gene VvBAS1, leading to effective mitigation of reactive oxygen species.

Overwintering covered with soil or avoiding burial of wine grapes under cold stress: Chinese wine industry's past and future, challenges and opportunities

In northwest China, where winter is extremely cold and the grapevine is vulnerable to freezing damage, the application of soil covering has promoted the vigorous development of the local grape and wine industries. However, in recent years, the negative effects of burying soil for cold protection on the environment have gradually emerged. In some viticultural regions, the phenomenon of "summer forest, winter desert" has appeared. Therefore, it is urgent for the Chinese grape industry to find a better solution to overwinter safely and environmentally friendly. This review summarizes the advantages and disadvantages of widely used solutions to overwinter such as covering vines with soil, breeding of cold-resistant grapes, cold-resistant cultivation model, physical and chemical covering materials, and protected grape facilities were reviewed. Future overwintering measures were proposed which avoid burial and grape overwintering research directions. It also provides a theoretical foundation and technical support to improve grape yield and quality in northwest China.

Responses of sorghum to cold stress: A review focused on molecular breeding

Climate change has led to the search for strategies to acclimatize plants to various abiotic stressors to ensure the production and quality of crops of commercial interest. Sorghum is the fifth most important cereal crop, providing several uses including human food, animal feed, bioenergy, or industrial applications. The crop has an excellent adaptation potential to different types of abiotic stresses, such as drought, high salinity, and high temperatures. However, it is susceptible to low temperatures compared with other monocotyledonous species. Here, we have reviewed and discussed some of the research results and advances that focused on the physiological, metabolic, and molecular mechanisms that determine sorghum cold tolerance to improve our understanding of the nature of such trait. Questions and opportunities for a comprehensive approach to clarify sorghum cold tolerance or susceptibility are also discussed.

Identification and Analysis of the CBF Gene Family in Three Species of Acer under Cold Stress

The C-Repeat Binding Factor (CBF) gene family has been identified and characterized in multiple plant species, and it plays a crucial role in responding to low temperatures. Presently, only a few studies on tree species demonstrate the mechanisms and potential functions of CBFs associated with cold resistance, while our study is a novel report on the multi-aspect differences of CBFs among three tree species, compared to previous studies. In this study, genome-wide identification and analysis of the CBF gene family in Acer truncatum, Acer pseudosieboldianum, and Acer yangbiense were performed. The results revealed that 16 CBF genes (five ApseCBFs, four AcyanCBFs, and seven AtruCBFs) were unevenly distributed across the chromosomes, and most CBF genes were mapped on chromosome 2 (Chr2) and chromosome 11 (Chr11). The analysis of phylogenetic relationships, gene structure, and conserved motif showed that 16 CBF genes could be clustered into three subgroups; they all contained Motif 1 and Motif 5, and most of them only spanned one exon. The cis-acting elements analysis showed that some CBF genes might be involved in hormone and abiotic stress responsiveness. In addition, CBF genes exhibited tissue expression specificity. High expressions of ApseCBF1, ApseCBF3, AtruCBF1, AtruCBF4, AtruCBF6, AtruCBF7, and ApseCBF3, ApseCBF4, ApseCBF5 were detected on exposure to low temperature for 3 h and 24 h. Low expressions of AtruCBF2, AtruCBF6, AtruCBF7 were detected under cold stress for 24 h, and AtruCBF3 and AtruCBF5 were always down-regulated under cold conditions. Taken together, comprehensive analysis will enhance our understanding of the potential functions of the CBF genes on cold resistance, thereby providing a reference for the introduction of Acer species in our country.