Plant Gene and Trait 2024, Vol.15, No.2, 52-61 http://genbreedpublisher.com/index.php/pgt 53 2 Basics of Epigenetic Mechanisms in Trees 2.1 Understanding epigenetic changes: DNA methylation, histone modification, RNA-associated silencing Epigenetic changes are crucial for the regulation of gene expression in trees, particularly in response to environmental stress. DNA methylation, histone modification, and RNA-associated silencing are the primary mechanisms through which these changes occur. DNA methylation involves the addition of a methyl group to the DNA molecule, typically at cytosine bases, which can suppress gene expression. Histone modifications, such as acetylation and methylation, alter the chromatin structure, thereby influencing gene accessibility and transcription. RNA-associated silencing involves small RNA molecules that can degrade mRNA or inhibit its translation, thus regulating gene expression post-transcriptionally (Narasimhan et al., 2015; Wan et al., 2015). 2.2 Role of epigenetics in gene regulation during stress responses Epigenetic modifications play a significant role in how trees respond to various stressors, such as drought, salinity, and pathogen attacks. These modifications can activate or repress specific genes that are involved in stress responses, enabling trees to adapt to changing environmental conditions. For instance, during drought stress, DNA methylation patterns can change to regulate genes involved in water conservation and root growth. Similarly, histone modifications can activate defense-related genes in response to pathogen attacks, enhancing the tree's ability to resist infections (Ozdemir et al., 2002; Jones and Grover, 2004). 2.3 Evolutionary implications of epigenetic modifications in trees The evolutionary implications of epigenetic modifications in trees are profound. These modifications can be heritable, meaning that they can be passed down to subsequent generations, thereby influencing the evolutionary trajectory of tree populations (Kurpisz and Pawłowski, 2022). Epigenetic changes can provide a rapid response mechanism to environmental changes, offering a form of plasticity that genetic mutations alone cannot provide. This ability to quickly adapt to environmental stressors through epigenetic mechanisms can enhance the survival and reproductive success of trees, contributing to their long-term evolutionary fitness (Stuzin et al., 2000; Kang et al., 2020). 3 Environmental Stressors and Epigenetic Responses 3.1 Types of environmental stresses affecting trees Trees are subjected to a variety of environmental stressors that can significantly impact their growth, development, and survival. These stressors include abiotic factors such as drought, extreme temperatures, and pollution, as well as biotic factors like pests and diseases. Each type of stress can trigger specific physiological and molecular responses in trees, which are often mediated by epigenetic modifications. 3.2 Epigenetic adaptations to drought and water scarcity Drought and water scarcity are among the most critical environmental stressors affecting trees. Epigenetic mechanisms, such as DNA methylation, histone modifications, and non-coding RNAs, play a crucial role in enabling trees to adapt to these conditions. For instance, DNA methylation patterns can change in response to water deficit, leading to the activation or repression of genes involved in water use efficiency and stress tolerance. Histone modifications can also alter chromatin structure, thereby regulating the expression of drought-responsive genes. These epigenetic changes can be stable and heritable, allowing trees to "remember" past drought events and respond more effectively to future water scarcity (Narasimhan et al., 2015; Wan et al., 2015). 3.3 Responses to temperature extremes and pollution Temperature extremes, including both high and low temperatures, pose significant challenges to tree survival (Figure 1) (Kurpisz and Pawłowski, 2022). Epigenetic modifications are essential for trees to cope with these stresses. For example, histone acetylation and methylation can regulate the expression of heat shock proteins and other stress-responsive genes, enabling trees to withstand high temperatures. Similarly, cold stress can induce changes in DNA methylation and histone modifications, which help in the activation of cold-responsive genes and the stabilization of cellular structures (Ozdemir et al., 2002; Jones and Grover, 2004). Pollution, particularly from heavy metals and other toxic compounds, also exerts stress on trees. Epigenetic responses to pollution include changes in DNA methylation and histone modifications that can either protect the genome from damage or
RkJQdWJsaXNoZXIy MjQ4ODYzMg==