1 Introduction

Understanding stress resistance in trees is crucial for environmental sustainability, particularly in the face of climate change. Trees play a vital role in maintaining ecological balance, providing habitat, and supporting biodiversity. However, abiotic stresses such as drought, salinity, and cold significantly impact tree growth and survival, thereby affecting forest ecosystems and the services they provide. Enhancing the stress resistance of trees can lead to more resilient forests, which are better equipped to withstand environmental changes and continue to provide essential ecosystem services (Pretzsch et al., 2013; Polle et al., 2019; Bhusal et al., 2021).

Studying tree responses to abiotic stresses presents several challenges. One major challenge is the complexity of stress responses, which involve intricate networks of genes and signaling pathways. For instance, drought and salinity stress responses in trees involve multiple genes and regulatory networks that are not yet fully understood (Benny et al., 2020; Bano et al., 2022). Additionally, the variability in stress responses among different tree species and even within species complicates the identification of universal resistance mechanisms (Zhang et al., 2020; Yousefi et al., 2022). Field studies are also limited, making it difficult to translate laboratory findings into practical applications for forest management (Polle et al., 2019). Moreover, trees often face multiple stresses simultaneously, which can interact in unpredictable ways, further complicating the study of stress resistance (Jia et al., 2016).

The primary objective of this systematic study is to analyze and synthesize information on key resistance genes involved in drought, salt, and cold stress in trees. By integrating findings from various studies, this study aims to identify common and unique genetic mechanisms that confer resistance to these abiotic stresses. This comprehensive analysis will provide insights into the molecular basis of stress resistance, highlight potential targets for genetic improvement, and suggest future research directions to enhance the resilience of forest trees.

2 Genetic Basis of Stress Resistance in Trees

2.1 Overview of genetic mechanisms underpinning resistance traits

The genetic mechanisms that underpin stress resistance in trees are multifaceted and involve a complex interplay of various genes and regulatory networks. Trees have evolved sophisticated mechanisms to cope with abiotic stresses such as drought, salt, and cold, which are critical for their survival and productivity. These mechanisms include osmotic adjustment, antioxidative defense, and hormonal regulation, which collectively enhance the tree's ability to withstand adverse environmental conditions (Bhusal et al., 2021; Bano et al., 2022). For instance, the abscisic acid (ABA) signaling pathway plays a crucial role in stress sensing and response, activating downstream transcription factors that regulate stress-responsive genes (Polle et al., 2019; Gao et al., 2019). Additionally, the integration of transcriptomic and genomic data has provided insights into the conserved and unique genetic responses to different stresses acROSs various tree species (Benny et al., 2020; Bano et al., 2022).

2.2 Key genes involved in drought, salt, and cold resistance

Several key genes have been identified that contribute to drought, salt, and cold resistance in trees. For drought resistance, genes involved in osmotic adjustment, such as those regulating proline and other osmolytes, are crucial. In salt stress, genes associated with ion transport and sequestration, such as those encoding for sodium transporters and vacuolar proton pumps, play significant roles (Zhang et al., 2020). Cold resistance is often mediated by genes involved in the synthesis of cryoprotective proteins and antifreeze proteins (Chen et al., 2013; Jin et al., 2017). Notable examples include the WRKY transcription factors, which are involved in both drought and salt stress responses (Gao et al., 2019), and the NAC transcription factors, which play roles in cold and drought tolerance by interacting with other stress-responsive genes. Additionally, calcium-dependent protein kinases (CDPKs) and mitogen-activated protein kinase kinase kinases (MAPKKKs) have been shown to modulate stress responses by regulating reactive oxygen species (ROS) and other signaling molecules (Chen et al., 2013).

2.3 Methods for identifying and characterizing resistance genes

The identification and characterization of resistance genes in trees have been greatly facilitated by advances in molecular biology and bioinformatics. Transcriptome meta-analysis is a powerful approach that integrates data from multiple studies to identify differentially expressed genes under stress conditions (Benny et al., 2020). This method allows for the identification of conserved stress-responsive genes acROSs different species and conditions. Functional genomics approaches, such as gene overexpression and silencing, have been employed to validate the roles of candidate genes in stress tolerance (Chen et al., 2013; Gao et al., 2019). Additionally, techniques like yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays are used to study protein-protein interactions and elucidate the regulatory networks involved in stress responses (Jin et al., 2017). Chromosome mapping and the identification of molecular markers are also crucial for breeding programs aimed at developing stress-resistant tree cultivars.

3 Drought Resistance Mechanisms in Trees

3.1 Physiological and biochemical pathways influenced by drought resistance genes

Drought resistance in trees involves a complex interplay of physiological and biochemical pathways. Key regulatory genes and transcription factors play crucial roles in modulating these pathways to enhance drought tolerance (Figure 1). For instance, the Dehydration-responsive element D (DRE1D) and ethylene response factor (ERF61) genes have been identified as significant contributors to drought stress resistance in cotton, influencing various stress-responsive molecular networks (Bano et al., 2022). Similarly, in Arabidopsis thaliana, transcription factors such as HSF, AP2/ERF, and C2H2 have been shown to play critical roles in drought stress response mechanisms, highlighting the importance of transcriptional regulation in drought tolerance. Additionally, the WRKY transcription factor WRKY8 in Solanum lycopersicum has been found to enhance drought tolerance by regulating stress-responsive genes and maintaining higher water content in leaves (Gao et al., 2019).

Figure 1 Network analysis of differentially expressed genes encoding transcription factors detected in salt and drought stresses (Adopted from Ghorbani et al., 2019)

Figure 1 shows the network analysis of differentially expressed transcription factor genes under salt and drought stress. Each color of the node in the figure represents a specific transcription factor family, such as AP2/ERF, MYB, NAC, etc., showing the interactions and connections between them. Larger nodes and thicker lines indicate the central role or strong interactions of transcription factors in responding to these stress conditions, revealing the complex regulatory mechanisms of plant response to environmental stress.

3.2 Case studies: genetic adaptations to drought conditions

Several case studies have demonstrated the genetic adaptations of trees to drought conditions. In Populus euphratica, three stress-responsive NAC transcription factors (PeNAC034, PeNAC045, and PeNAC036) have been shown to differentially regulate drought tolerance (Francescantonio et al., 2020). Overexpression of PeNAC036 in Arabidopsis increased tolerance to drought, while PeNAC034 overexpression led to increased sensitivity, indicating the complex regulatory roles of these genes (Lu et al., 2018). Another study on Populus euphratica identified a calcium-dependent protein kinase gene, PeCPK10, which conferred enhanced drought tolerance when overexpressed in Arabidopsis, suggesting its potential role as a positive regulator of drought stress response (Chen et al., 2013). Furthermore, the WRKY8 transcription factor in tomato has been shown to alleviate drought-induced wilting and chloROSis, demonstrating its role in enhancing drought resistance through the regulation of osmotic substances and antioxidant enzyme activities (Jia et al., 2016).

3.3 Technological advances in drought resistance research

Technological advances have significantly contributed to the understanding and improvement of drought resistance in trees. Transcriptome meta-analysis has emerged as a powerful tool to unravel the stress-responsive molecular networks in crops. For example, a meta-analysis of transcriptome studies in cotton has identified key regulatory hub genes and pathways associated with drought stress, providing potential candidate genes for further functional studies (Bano et al., 2022). Similarly, microarray expression profile analysis in Arabidopsis has revealed the central role of transcription factors and differentially expressed genes in drought stress response, offering insights into the molecular mechanisms underlying drought tolerance (Ghorbani et al., 2019). Additionally, the use of virus-induced gene silencing (VIGS) and overexpression techniques in cotton and N. benthamiana has facilitated the functional characterization of genes like GhRaf19, which negatively regulates drought tolerance by modulating reactive oxygen species (ROS) (Jia et al., 2016). These technological advancements are paving the way for the development of genetically improved tree genotypes with enhanced drought resistance.

4 Salt Resistance Mechanisms in Trees

4.1 Genetic modifiers of salt tolerance: ion transport and osmotic regulation

Salt tolerance in trees involves complex genetic and physiological mechanisms that help mitigate the detrimental effects of high salinity. One of the primary strategies is the regulation of ion transport and osmotic balance. For instance, the WRKY transcription factor SlWRKY8 in tomato has been shown to enhance salt tolerance by increasing the levels of osmotic substances like proline and activating stress-responsive genes such as SlAREB, SlDREB2A, and SlRD29 (Gao et al., 2019). Similarly, the sweetpotato β-amylase gene IbBAM1.1 enhances salt stress resistance by regulating reactive oxygen species (ROS) homeostasis and osmotic balance, promoting the accumulation of osmoprotectants like maltose and proline (Zhu et al., 2021). In rice, high performance photosynthesis and better osmotic adjustment have been associated with salt tolerance, as observed in near isogenic lines carrying drought tolerance QTL (Nounjan et al., 2018). These genetic modifiers play crucial roles in maintaining ion homeostasis and osmotic regulation, which are essential for salt tolerance in trees.

4.2 Case studies: successful salt resistance breeding and genetic engineering

Several case studies highlight the success of breeding and genetic engineering in enhancing salt resistance in trees. For example, the overexpression of the NAC transcription factor PeNAC036 in Populus euphratica has been shown to increase tolerance to salt and drought by upregulating stress-responsive genes such as COR47, RD29B, ERD11, RD22, and DREB2A (Lu et al., 2018). Another study demonstrated that silencing the Raf-like MAPKKK gene GhRaf19 in cotton enhanced tolerance to salt stress by reducing ROS accumulation and increasing the expression of ROS-related genes (Jia et al., 2016). These case studies illustrate the potential of genetic engineering and selective breeding in developing salt-resistant tree varieties.

4.3 Challenges in enhancing salt resistance through genetic approaches

Despite the promising results from genetic studies, several challenges remain in enhancing salt resistance in trees through genetic approaches. One major challenge is the complexity of stress responses, as trees often face multiple abiotic stresses simultaneously, which can complicate the effectiveness of single-gene modifications. Additionally, field studies are scarce, and the positive effects observed under laboratory conditions may not always translate to real-world environments where trees are exposed to variable and prolonged stress conditions (Yuan et al., 2020). Another challenge is the potential trade-off between growth and stress resistance, as enhancing one trait may negatively impact the other. Therefore, a better understanding of the intricate networks that regulate stress responses and the development of stress-inducible promoters may be necessary to optimize the balance between growth and defense (Golldack et al., 2011).

5 Cold Resistance Mechanisms in Trees

5.1 Cold acclimation processes influenced by genetic factors

Cold acclimation in trees involves a series of genetic and physiological changes that enhance their ability to withstand low temperatures. Genetic factors play a crucial role in these processes. For instance, the expression of dehydration-responsive element binding protein (DREB) genes, such as OsDREB1C, OsDREB1E, and OsDREB1G, has been shown to be key regulators of cold acclimation and freezing tolerance in rice, which can be extrapolated to trees (Wang et al., 2022). Additionally, the upregulation of cold-responsive genes like RD29B and MbCBF2 in transgenic plants overexpressing PeCPK10 from Populus euphratica indicates the importance of these genes in cold stress response (Figure 2) (Chen et al., 2013). Furthermore, transcriptome analyses in apple trees have identified differentially expressed genes (DEGs) that are enriched in metabolic processes and signal transduction components, which are crucial for cold acclimation.

Figure 2 Overexpression of MbCBF2 improves the cold resistance of Arabidopsis thaliana (Adopted from Li et al., 2022) Image caption: (A) Semi-quantitative observation using MbCBF2-specific primers (MbCBF2+) and non-specific primers (MbCBF2-). (B) Phenotypes of MbCBF2 transgenic Arabidopsis lines under low temperature stress and recovery conditions. (C) Low temperature There is a significant difference in the survival rate of transgenic Arabidopsis (S1, S4 and S5) and WT lines under the conditions (**, p≤0.01) (Adopted from Li et al., 2022)

Genetic factors play an important role in studying the adaptation mechanisms of trees to cold environments. Li et al. (2022) By studying model plants such as Arabidopsis thaliana, scientists found that specific genes such as MbCBF2 play a key role in improving the low temperature tolerance of plants. Compared with wild type and control, transgenic plants (S1, S4, S5 ) maintained good growth status after low-temperature treatment and during recovery. Overexpression of this gene can significantly enhance the plant's resistance to cold damage. This discovery provides an important genetic perspective for understanding the cold-resistant adaptability of plants.

5.2 Case studies: genomic insights into cold resistance strategies

Several case studies provide insights into the genomic strategies trees employ to resist cold stress. For example, a study on Populus euphratica identified a calcium-dependent protein kinase gene, PeCPK10, which enhances freezing tolerance by promoting the expression of abscisic acid-responsive and other stress-responsive genes (Chen et al., 2013). Another study on rice identified the OsMYB3R-2 gene, which increases tolerance to freezing, drought, and salt stress by acting as a master switch in stress tolerance (Dai et al., 2007). In cotton, the Raf-like MAPKKK gene GhRaf19 was found to positively regulate resistance to cold stress by modulating reactive oxygen species (ROS) levels, highlighting the role of ROS in cold stress response (Jia et al., 2016). Additionally, integrated transcriptomic and metabolomic analyses in pepper species revealed key genes and metabolic pathways involved in cold stress response, such as the MAPK signaling pathway and flavonoid biosynthesis, which are essential for cold tolerance (Gao et al., 2022).

5.3 Innovations in gene editing for improving cold resistance

Recent advancements in gene editing technologies, such as CRISPR/Cas9, offer promising avenues for improving cold resistance in trees. For instance, the identification of conserved cold tolerance-related genes acROSs different species provides potential targets for gene editing to enhance cold resistance (Yousefi et al., 2022). The use of CRISPR/Cas9 to develop molecular markers for breeding cold-resistant tree varieties is a significant innovation in this field. Moreover, the overexpression of genes involved in stress sensing and signaling, such as those in the abscisic acid core pathway, has been shown to generally enhance drought and salt stress tolerance, which could be applied to cold stress as well (Polle et al., 2019). These biotechnological approaches aim to recruit a suite of defense systems to improve cold resistance in trees, although field studies are necessary to validate their effectiveness under natural conditions.

6 Case Studies: Integrative Genetic Studies on Tree Stress Resistance

Recent integrative genetic studies have provided significant insights into the mechanisms underlying tree stress resistance. For instance, a meta-analysis of RNA-Seq samples from various fruit tree species identified key genes involved in drought and salinity tolerance. This study highlighted the conserved role of 750 genes in salinity resistance and 683 genes in drought resistance, with 82 genes commonly regulated under both stresses. The findings emphasized the importance of pathways related to defense response, drug transmembrane transport, and metal ion binding, as well as hormonal cROSstalk in stress responses (Benny et al., 2020). Another study focused on the WRKY transcription factor WRKY8 in tomatoes, demonstrating its role in enhancing resistance to pathogen infection and tolerance to drought and salt stresses through the regulation of stress-responsive genes and antioxidant enzyme activities (Gao et al., 2019).

6.1 Comprehensive analysis of multi-stress resistant varieties

Comprehensive analyses of multi-stress resistant varieties have revealed the complex interplay of genetic factors that confer resistance to multiple abiotic stresses (Table 1). For example, a study on cotton identified key regulatory hub genes involved in drought and salt stress tolerance, such as NSP2, DRE1D, and ERF61, which are associated with significant differential expression in response to these stresses (Bano et al., 2022). Similarly, research on Populus euphratica identified a calcium-dependent protein kinase gene, PeCPK10, which enhances both drought and cold stress tolerance by promoting stomatal closure and upregulating stress-responsive genes (Chen et al., 2013). These studies underscore the potential of leveraging multi-stress resistant genes to develop robust tree varieties.

Table 1 Classification of the genomic architecture of resistance to biotic stress in tree species

6.2 Interactions between different stress resistance genes

The interactions between different stress resistance genes play a crucial role in determining the overall stress tolerance of trees. For instance, the study on GhRaf19, a Raf-like MAPKKK gene in cotton (Jia et al., 2016), revealed its dual role in modulating tolerance to drought, salt, and cold stresses. GhRaf1 negatively regulates drought and salt tolerance by reducing ROS accumulation, while positively regulating cold stress resistance by enhancing ROS-related antioxidant gene expression. Additionally, the meta-analysis of cold stress tolerance genes acROSs various crops identified conserved pathways involving protein modifications, hormone metabolism, and secondary metabolism, which are crucial for cold tolerance (Yousefi et al., 2022). These findings highlight the intricate genetic networks that govern multi-stress resistance in trees.

6.3 Implications of multi-trait genetic studies for forestry practices

The insights gained from multi-trait genetic studies have significant implications for forestry practices. Understanding the genetic basis of stress resistance can inform the selection and breeding of tree species for afforestation programs (Verslues et al., 2006). For example, the evaluation of drought resistance in eleven tree species identified Korean pine as highly resistant, while species like sawtooth oak and hinoki cypress were highly susceptible (Bhusal et al., 2021). This knowledge can guide the selection of species for planting in areas prone to drought. Furthermore, the identification of stress-inducible promoters and the use of biotechnological approaches to overexpress stress-responsive genes can enhance the resilience of forest trees to environmental stresses (Polle et al., 2019). Integrating these genetic insights into forestry practices can contribute to the establishment of sustainable and resilient forest ecosystems.

7 Technological Advances in Genetic Research

7.1 Role of next-generation sequencing in stress resistance studies

Next-generation sequencing (NGS) has revolutionized the field of genetic research, providing unprecedented insights into the genetic basis of stress resistance in trees. NGS technologies enable the comprehensive analysis of genomes, transcriptomes, and epigenomes, facilitating the identification of key genes and regulatory networks involved in stress responses. For instance, whole-genome resequencing of rice cultivars with contrasting responses to drought and salinity stress has identified numerous single-nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) that are associated with stress tolerance traits (Jain et al., 2014). Similarly, transcriptome-wide analyses using RNA-Seq have revealed differentially expressed genes and pathways that contribute to drought and salinity tolerance in various fruit tree species (Benny et al., 2020). These studies underscore the critical role of NGS in uncovering the genetic underpinnings of stress resistance, thereby aiding in the development of stress-tolerant tree cultivars.

7.2 Contributions of bioinformatics and systems biology to understanding complex traits

Bioinformatics and systems biology approaches are indispensable for deciphering the complex genetic networks underlying stress resistance in trees. By integrating large-scale omics data, these approaches enable the identification of key regulatory genes and pathways involved in stress responses. For example, a meta-analysis of transcriptome data in cotton has identified hub genes and regulatory networks associated with drought and salt stress tolerance, providing potential targets for genetic improvement (Bano et al., 2022). Similarly, bioinformatics pipelines have been used to map stress-responsive genes in fruit trees, revealing conserved molecular responses to drought and salinity. Systems biology approaches, such as gene co-expression analysis, have also been employed to identify stress-responsive gene families in potato, highlighting their roles in drought and heat tolerance (Chen et al., 2019). These contributions demonstrate the power of bioinformatics and systems biology in advancing our understanding of complex stress resistance traits in trees.

7.3 Future technologies poised to transform tree genetic research

Emerging technologies hold great promise for further advancing tree genetic research and enhancing stress resistance. CRISPR/Cas9 genome editing, for instance, offers precise and efficient tools for modifying stress-responsive genes, enabling the development of trees with improved tolerance to drought, salinity, and cold (Yousefi et al., 2022). Additionally, advanced phenotyping platforms, such as high-throughput imaging and sensor technologies, can provide detailed insights into the physiological and biochemical responses of trees to stress, facilitating the identification of key traits associated with stress resistance (Bhusal et al., 2021). Furthermore, the integration of multi-omics data, including genomics, transcriptomics, proteomics, and metabolomics, will enable a more comprehensive understanding of the molecular mechanisms underlying stress responses, paving the way for the development of resilient tree species (Tiika et al., 2021). These future technologies are poised to transform tree genetic research, offering new avenues for enhancing stress resistance and ensuring the sustainability of forest ecosystems.

8 Breeding and Biotechnological Applications

8.1 Strategies for breeding stress-resistant tree varieties

Breeding stress-resistant tree varieties involves selecting and propagating trees that exhibit desirable traits under adverse environmental conditions. Traditional breeding methods have focused on selecting phenotypes with enhanced drought, salt, and cold resistance. For instance, studies have shown that trees with high leaf mass per area (LMA), photosynthetic rate (Pn), and midday leaf water potential (ΨMD) tend to exhibit higher drought resistance (Bhusal et al., 2021). Additionally, the identification of conserved genes involved in stress responses acROSs different species can aid in the development of molecular markers for breeding programs (Benny et al., 2020; Yousefi et al., 2022).

Recent advancements in genomics and transcriptomics have enabled the identification of key genes and regulatory networks involved in stress tolerance. For example, a meta-analysis of RNA-Seq data from various fruit tree species identified genes that are commonly regulated under drought and salinity stress, providing potential targets for breeding programs (Benny et al., 2020). Moreover, the integration of bioinformatics tools and large-scale field studies can help in understanding the complex interactions between different stress factors and tree physiology, thereby optimizing breeding strategies (Polle et al., 2019).

8.2 Genetic engineering and CRISPR applications in developing resistance traits

Genetic engineering, particularly through the use of CRISPR/Cas9 technology, has revolutionized the development of stress-resistant tree varieties. CRISPR/Cas9 allows for precise editing of genes involved in stress responses, enabling the creation of trees with enhanced tolerance to drought, salinity, and cold. For instance, the overexpression of specific transcription factors, such as WRKY8, has been shown to improve resistance to both biotic and abiotic stresses in tomato, suggesting similar applications in trees (Gao et al., 2019).

The use of CRISPR/Cas9 has been extensively studied in model plants and crops, with promising results in enhancing stress tolerance. For example, the editing of genes involved in the abscisic acid signaling pathway has been shown to improve drought and salt tolerance in various plant species (Nascimento et al., 2023). Additionally, the identification of key regulatory genes through transcriptome analysis can provide new targets for genetic engineering. In apple trees, for instance, the overexpression of certain genes has been linked to improved resistance to multiple stresses, including drought, cold, and salinity.

8.3 Ethical and practical considerations in genetic manipulation of trees

While genetic engineering offers significant potential for developing stress-resistant tree varieties, it also raises ethical and practical considerations. One major concern is the potential impact on biodiversity and ecosystem balance. The introduction of genetically modified trees into natural environments could lead to unintended consequences, such as the displacement of native species or the disruption of local ecosystems (Wang et al., 2003). Moreover, the long-term effects of genetic modifications on tree health and productivity are still not fully understood. Field studies are essential to evaluate the performance of genetically engineered trees under natural conditions and to ensure that the modifications do not negatively affect other important traits, such as growth rate and wood quality (Polle et al., 2019). Ethical considerations also include the potential for gene flow from genetically modified trees to wild relatives, which could result in the spread of modified traits beyond the intended population. Regulatory frameworks and guidelines are necessary to address these concerns and to ensure the responsible use of genetic engineering in forestry (Nascimento et al., 2023). In conclusion, while breeding and biotechnological applications hold great promise for enhancing tree stress resistance, careful consideration of ethical and practical issues is essential to ensure sustainable and responsible implementation.

9 Future Research Directions in Tree Stress Resistance

9.1 Unexplored areas in the genetics of tree stress resistance

Despite significant advancements in understanding tree stress resistance, several genetic aspects remain underexplored. For instance, the role of specific transcription factors and signaling pathways in stress responses needs further investigation. The WRKY transcription factors, such as SlWRKY8, have shown promise in mediating drought and salt stress tolerance in Solanum lycopersicum, suggesting similar potential in trees (Gao et al., 2019). Additionally, the Raf-like MAPKKK gene, GhRaf19, has been identified to regulate stress responses in cotton, indicating that similar genes in trees could be crucial for enhancing stress resistance (Jia et al., 2016). Moreover, the expansin gene family in potato has revealed stress-responsive genes that could be explored in tree species for their role in drought and heat tolerance (Chen et al., 2019). Future research should focus on identifying and characterizing these genes in various tree species to develop a comprehensive understanding of their roles in stress resistance.

9.2 Potential for integrative and multi-disciplinary research approaches

Integrative and multi-disciplinary research approaches hold great potential for advancing tree stress resistance. Combining genomics, transcriptomics, and proteomics can provide a holistic view of the molecular mechanisms underlying stress responses. For example, a meta-analysis of transcriptome studies in cotton has identified key regulatory hub genes involved in drought and salt stress responses, which could be applied to tree species (Bano et al., 2022). Additionally, integrating ecological and evolutionary genomics can enhance our understanding of biotic stress resistance and promote the breeding of resistant phenotypes (Guevara-Escudero et al., 2021). Collaborative efforts between molecular biologists, ecologists, and breeders can lead to the development of innovative strategies for improving tree stress resistance.

9.3 Funding and policy support for advanced genetic research

To achieve significant progress in tree stress resistance, increased funding and policy support for advanced genetic research are essential. Large-scale experimental field studies are necessary to validate laboratory findings and assess the usability of genetic modifications under real-world conditions (Polle et al., 2019). Furthermore, funding should support the development of biotechnological tools and resources, such as high-throughput sequencing and gene editing technologies, to facilitate the identification and manipulation of stress resistance genes. Policymakers should prioritize research initiatives that focus on sustainable forest management and the conservation of natural habitats, particularly in the face of increasing climate change-induced stresses (Bhusal et al., 2021). By fostering a supportive environment for advanced genetic research, we can develop resilient tree species capable of withstanding various abiotic stresses.

10 Concluding Remarks

The comprehensive analysis of drought, salt, and cold resistance genes in trees has revealed significant insights into the molecular and physiological mechanisms underlying stress tolerance. Key findings indicate that osmotic adjustment, antioxidative defense, and increased water use efficiency are crucial for drought tolerance. Additionally, hormonal cROSstalk plays a vital role in fine-tuning plant responses to both drought and salinity, with specific genes being upregulated or downregulated in response to these stresses. The identification of hub genes and pathways, such as those involving nodulation signaling pathways and ethylene response factors, further elucidates the complex networks that confer stress resistance. Moreover, the role of calcium-dependent protein kinases and Raf-like MAPKKKs in modulating stress responses highlights the importance of these genes in enhancing tolerance to multiple abiotic stresses.

This study has made several key contributions to the fields of tree physiology and forestry. Firstly, it has synthesized current knowledge on the genetic and molecular bases of stress resistance, providing a valuable resource for researchers and practitioners. By highlighting the importance of specific genes and pathways, this study offers potential targets for genetic engineering and breeding programs aimed at developing stress-resistant tree species. Furthermore, the study underscores the necessity of large-scale field studies to validate laboratory findings and assess the practical applicability of genetic modifications under natural conditions. The insights gained from this study can inform afforestation and reforestation efforts, particularly in regions prone to climatic stresses, thereby contributing to the establishment of sustainable and resilient forest ecosystems.

Future research should focus on several key areas to advance our understanding and application of tree stress resistance genes. Firstly, there is a need for more extensive field studies to evaluate the performance of genetically modified trees under diverse environmental conditions and stress combinations. Additionally, research should aim to elucidate the interactions between different stress resistance mechanisms and their cumulative effects on tree physiology and growth. The development of stress-inducible promoters and other biotechnological tools can optimize the balance between growth and defense, enhancing the practical utility of genetic modifications. Furthermore, exploring the potential of inter-specific facilitation and mixed-species stands could offer novel strategies for enhancing stress resistance in forest ecosystems. Finally, integrating genomic, transcriptomic, and phenotypic data will be crucial for identifying and validating new candidate genes for stress resistance, paving the way for the development of more resilient tree species.

Acknowledgments

The author extends sincere thanks to two anonymous peer reviewers for their feedback on the manuscript of this paper.

Conflict of Interest Disclosure

The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

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