PpCBF3 from Cold-Tolerant Kentucky Bluegrass Involved in Freezing Tolerance Associated with Up-Regulation of Cold-Related Genes in Transgenic Arabidopsis thaliana

SVALKA: A Long Noncoding Cis-Natural Antisense RNA That Plays a Role in the Regulation of the Cold Response of Arabidopsis thaliana

RNA plays important roles in the regulation of gene expression in response to environmental stimuli. SVALKA, a long noncoding cis-natural antisense RNA, is a key component of regulating the response to cold temperature in Arabidopsis thaliana. There are three mechanisms through which SVALKA fine tunes the transcriptional response to cold temperatures. SVALKA regulates the expression of the CBF1 (C-Repeat Dehydration Binding Factor 1) transcription factor through a collisional transcription mechanism and a dsRNA and DICER mediated mechanism. SVALKA also interacts with Polycomb Repressor Complex 2 to regulate the histone methylation of CBF3. Both CBF1 and CBF3 are key components of the COLD REGULATED (COR) regulon that direct the plant's response to cold temperature over time, as well as plant drought adaptation, pathogen responses, and growth regulation. The different isoforms of SVALKA and its potential to form dynamic RNA conformations are important features in regulating a complex gene network in concert with several other noncoding RNA. This review will summarize the three mechanisms through which SVALKA participates in gene regulation, describe the ways that dynamic RNA structures support the function of regulatory noncoding RNA, and explore the potential for improving agricultural genetic engineering with a better understanding of the roles of noncoding RNA.

Coping with the cold: unveiling cryoprotectants, molecular signaling pathways, and strategies for cold stress resilience

Low temperature stress significantly threatens crop productivity and economic sustainability. Plants counter this by deploying advanced molecular mechanisms to perceive and respond to cold stress. Transmembrane proteins initiate these responses, triggering a series of events involving secondary messengers such as calcium ions (Ca2+), reactive oxygen species (ROS), and inositol phosphates. Of these, calcium signaling is paramount, activating downstream phosphorylation cascades and the transcription of cold-responsive genes, including cold-regulated (COR) genes. This review focuses on how plants manage freeze-induced damage through dual strategies: cold tolerance and cold avoidance. Tolerance mechanisms involve acclimatization to decreasing temperatures, fostering gradual accumulation of cold resistance. In contrast, avoidance mechanisms rely on cryoprotectant molecules like potassium ions (K+), proline, glycerol, and antifreeze proteins (AFPs). Cryoprotectants modulate intracellular solute concentration, lower the freezing point, inhibit ice formation, and preserve plasma membrane fluidity. Additionally, these molecules demonstrate antioxidant activity, scavenging ROS, preventing protein denaturation, and subsequently mitigating cellular damage. By forming extensive hydrogen bonds with water molecules, cryoprotectants also limit intercellular water movement, minimizing extracellular ice crystal formation, and cell dehydration. The deployment of cryoprotectants is a key adaptive strategy that bolsters plant resilience to cold stress and promotes survival in freezing environments. However, the specific physiological and molecular mechanisms underlying these protective effects remain insufficiently understood. Therefore, this review underscores the need for further research to elucidate these mechanisms and assess their potential impact on crop productivity and sustainability, contributing to the progressive discourse in plant biology and environmental science.

ICE-CBF-COR Signaling Cascade and Its Regulation in Plants Responding to Cold Stress

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.

Transgenic crops for the agricultural improvement in Pakistan: a perspective of environmental stresses and the current status of genetically modified crops

Transgenic technologies have emerged as a powerful tool for crop improvement in terms of yield, quality, and quantity in many countries of the world. However, concerns also exist about the possible risks involved in transgenic crop cultivation. In this review, literature is analyzed to gauge the real intensity of the issues caused by environmental stresses in Pakistan. In addition, the research work on genetically modified organisms (GMOs) development and their performance is analyzed to serve as a guide for the scientists to help them select useful genes for crop transformation in Pakistan. The funding of GMOs research in Pakistan shows that it does not follow the global trend. We also present socio-economic impact of GM crops and political dimensions in the seed sector and the policies of the government. We envisage that this review provides guidelines for public and private sectors as well as the policy makers in Pakistan and in other countries that face similar environmental threats posed by the changing climate.

Meta-Analysis of the Effect of Overexpression of Dehydration-Responsive Element Binding Family Genes on Temperature Stress Tolerance and Related Responses

Dehydration-responsive element binding proteins are transcription factors that play a critical role in plant response to temperature stress. Over-expression of DREB genes has been demonstrated to enhance temperature stress tolerance. A series of physiological and biochemical modifications occur in a complex and integrated way when plants respond to temperature stress, which makes it difficult to assess the mechanism underlying the DREB enhancement of stress tolerance. A meta-analysis was conducted of the effect of DREB overexpression on temperature stress tolerance and the various parameters modulated by overexpression that were statistically quantified in 75 published articles. The meta-analysis was conducted to identify the overall influence of DREB on stress-related parameters in transgenic plants, and to determine how different experimental variables affect the impact of DREB overexpression. Viewed across all the examined studies, 7 of the 8 measured plant parameters were significantly (p ≤ 0.05) modulated in DREB-transgenic plants when they were subjected to temperature stress, while 2 of the 8 parameters were significantly affected in non-stressed control plants. The measured parameters were modulated by 32% or more by various experimental variables. The modulating variables included, acclimated or non-acclimated, type of promoter, stress time and severity, source of the donor gene, and whether the donor and recipient were the same genus. These variables all had a significant effect on the observed impact of DREB overexpression. Further studies should be conducted under field conditions to better understand the role of DREB transcription factors in enhancing plant tolerance to temperature stress.

Identification of genes from the ICE-CBF-COR pathway under cold stress in Aegilops-Triticum composite group and the evolution analysis with those from Triticeae

Adverse environmental conditions limit various aspects of plant growth, productivity, and ecological distribution. To get more insights into the signaling pathways under low temperature, we identified 10 C-repeat binding factors (CBFs), 9 inducer of CBF expression (ICEs) and 10 cold-responsive (CORs) genes from Aegilops-Triticum composite group under cold stress. Conserved amino acids analysis revealed that all CBF, ICE, COR contained specific and typical functional domains. Phylogenetic analysis of CBF proteins from Triticeae showed that these CBF homologs were divided into 11 groups. CBFs from Triticum were found in every group, which shows that these CBFs generated prior to the divergence of the subfamilies of Triticeae. The evolutionary relationship among the ICE and COR proteins in Poaceae were divided into four groups with high multispecies specificity, respectively. Moreover, expression analysis revealed that mRNA accumulation was altered by cold treatment and the genes of three types involved in the ICE-CBF-COR signaling pathway were induced by cold stress. Together, the results make CBF, ICE, COR genes family in Triticeae more abundant, and provide a starting point for future studies on transcriptional regulatory network for improvement of chilling tolerance in crop.

An Overview of Signaling Regulons During Cold Stress Tolerance in Plants

Plants, being sessile organisms, constantly withstand environmental fluctuations, including low-temperature, also referred as cold stress. Whereas cold poses serious challenges at both physiological and developmental levels to plants growing in tropical or sub-tropical regions, plants from temperate climatic regions can withstand chilling or freezing temperatures. Several cold inducible genes have already been isolated and used in transgenic approach to generate cold tolerant plants. The conventional breeding methods and marker assisted selection have helped in developing plant with improved cold tolerance, however, the development of freezing tolerant plants through cold acclimation remains an unaccomplished task. Therefore, it is essential to have a clear understanding of how low temperature sensing strategies and corresponding signal transduction act during cold acclimation process. Herein, we synthesize the available information on the molecular mechanisms underlying cold sensing and signaling with an aim that the summarized literature will help develop efficient strategies to obtain cold tolerant plants.

Gene Regulation and Signal Transduction in the ICE-CBF-COR Signaling Pathway during Cold Stress in Plants

Low temperature is an abiotic stress that adversely affects the growth and production of plants. Resistance and adaptation of plants to cold stress is dependent upon the activation of molecular networks and pathways involved in signal transduction and the regulation of cold-stress related genes. Because it has numerous and complex genes, regulation factors, and pathways, research on the ICE-CBF-COR signaling pathway is the most studied and detailed, which is thought to be rather important for cold resistance of plants. In this review, we focus on the function of each member, interrelation among members, and the influence of manipulators and repressors in the ICE-CBF-COR pathway. In addition, regulation and signal transduction concerning plant hormones, circadian clock, and light are discussed. The studies presented provide a detailed picture of the ICE-CBF-COR pathway.

A ThDREB gene from Tamarix hispida improved the salt and drought tolerance of transgenic tobacco and T. hispida

Dehydration-responsive element-binding (DREB) transcription factors are important abiotic stress tolerance related genes, and some reports on the roles of DREB have primarily addressed herbal plants. To explore the abiotic stress tolerance role of DREB (ThDREB) from Tamarix hispida, a ThDREB gene with a complete ORF of 783 bp that encodes a 28.74 kDa protein with 260 amino acids, was isolated and functionally annotated. ThDREB expression was highly induced by NaCl, PEG, NaHCO3 and CdCl2 treatments, and the highest expression level (369.2-fold of control) was found for the roots that were under NaCl stress for 6 h. The tobacco plants that were transformed by ThDREB were conferred with higher germination rates, fresh weights and root lengths than the wild type (WT) tobacco plants under NaCl and mannitol treatments. The total chlorophyll content (tcc), superoxide dismutase (SOD) and peroxidase (POD) activities were also higher in the transgenic lines in comparison with the WT, and the malondialdehyde (MDA) and H2O2 content, electrolyte leakage (EL) rate and ROS as tracked by staining were generated to a lesser degree in ThDREB transgenic plants than in the WT under NaCl and mannitol stress. Furthermore, the transient overexpression analysis of ThDREB in T. hispida also improved plant salt and drought tolerance in comparison with the empty vector-transformed lines. Our results indicated that ThDREB expression could effectively improve tolerance to salt and drought stress by enhancing the antioxidase activity that keeps the ROS at a low accumulation level and makes them easy to scavenge.

Dehydration responsive element binding transcription factors and their applications for the engineering of stress tolerance

Dehydration responsive element binding (DREB) factors or CRT element binding factors (CBFs) are members of the AP2/ERF family, which comprises a large number of stress-responsive regulatory genes. This review traverses almost two decades of research, from the discovery of DREB/CBF factors to their optimization for application in plant biotechnology. In this review, we describe (i) the discovery, classification, structure, and evolution of DREB genes and proteins; (ii) induction of DREB genes by abiotic stresses and involvement of their products in stress responses; (iii) protein structure and DNA binding selectivity of different groups of DREB proteins; (iv) post-transcriptional and post-translational mechanisms of DREB transcription factor (TF) regulation; and (v) physical and/or functional interaction of DREB TFs with other proteins during plant stress responses. We also discuss existing issues in applications of DREB TFs for engineering of enhanced stress tolerance and improved performance under stress of transgenic crop plants.

Both JrWRKY2 and JrWRKY7 of Juglans regia mediate responses to abiotic stresses and abscisic acid through formation of homodimers and interaction

WRKY transcription factors belong to a large protein family that is involved in diverse developmental processes and abiotic stress responses. Currently, there is little understanding of the role of WRKY transcription factors in regulatory mechanisms in plants, especially in the protein-protein interactions that are essential for biological regulatory functions and networks. In the present study, yeast one-hybrid, yeast two-hybrid, transient expression and quantitative RT-PCR were applied to investigate the potential characteristics of two WRKY proteins from Juglans regia, JrWRKY2 (GenBank Accession No. KU057089) and JrWRKY7 (GenBank Accession No. KP784651). JrWRKY2 and JrWRKY7 can form homodimers and interact with each other. JrWRKY2 and JrWRKY7 can bind to W-box motifs. Similarly high levels of transcription were found for JrWRKY2 and JrWRKY7 under NaCl and polyethylene glycol (PEG) stresses, as well as at different developmental stages, e.g., the pistil or terminal leaf. JrWRKY2 and JrWRKY7 were transiently overexpressed in an independent manner in the terminal leaf. Analyses of superoxide dismutase (SOD) and peroxidase (POD) activities, proline and malondialdehyde (MDA) contents, and electrolyte leakage rate showed that JrWRKY2 and JrWRKY7 overexpression improved plant tolerance to NaCl, PEG, abscisic acid, and cold stress. Additionally, JrWRKY2 and JrWRKY7 overexpression elevated transcription of SOD, POD, glutathione peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX), and MYB genes, but downregulated the expression of NAC. Overall, the results demonstrate that JrWRKY2 and JrWRKY7 are dimeric proteins that can form functional homodimers and interact with each other and that they are involved in abiotic stress responses.