Tree Genetics and Molecular Breeding 2025, Vol.15, No.3, 128-137 http://genbreedpublisher.com/index.php/tgmb 131 passed between cell divisions or generations, which is called “epigenetic memory” (He and Li, 2018; Sobral and Sampedro, 2022; Baduel et al., 2024). In plants such as Camellia oleifera, this memory enables the next generation to perform better in similar environments, such as stronger growth ability or higher oil content (Anastasiadi et al., 2021; Brukhin and Albertini, 2021). However, whether this kind of memory is stable and hereditary is still influenced by many factors. Some epigenetic markers are “reset to zero” during sexual reproduction, but some studies have found that under asexual reproduction or specific conditions, some markers can be stably passed on (Radford, 2018; Anastasiadi et al., 2021; Jo and Nodine, 2024). This intergenerational transmission ability provides a new direction for the breeding and adaptability improvement of economic crops such as Camellia oleifera. 5 Altitude and Oil Accumulation in Camellia oleifera 5.1 Comparative oil profiles from high- and low-altitude plantations In high-altitude areas, the fruit traits and oil quality of Camellia oleifera show significant differences. For instance, an analysis of 48 Camellia oleifera germplasm samples from the high-altitude areas in eastern Guizhou Province revealed significant variations in traits such as single fruit weight, fruit peel thickness, and the yields of fresh and dry seeds. Among them, the content of seed kernel oil has a significant positive correlation with the contents of palmitic acid and linoleic acid, but a negative correlation with the content of 11-eicosenoic acid. Some excellent individuals in high-altitude areas (such as QD-33, QD-34, QD-48) have high lipid content and good quality, and are very promising materials for breeding (Wan et al., 2024). In addition, by comparing the high-oil and low-oil Camellia oleifera seeds, it was found that there were also significant differences between the two in terms of oil content and fatty acid composition. Oleic acid accumulates more in high-oil seeds, which may be due to the coordinated work of multiple related genes, promoting the synthesis of oleic acid (Wu et al., 2019). 5.2 Influence of temperature and light on oil yield and quality Temperature and light are important environmental factors affecting the oil accumulation and quality of Camellia oleifera seeds. Research has found that the expression of the LEA gene family is enhanced in the later stage of embryonic development, and a large amount of LEA protein accumulates. These proteins not only participate in seed development and oil accumulation, but also respond to stresses such as drought and shading. qPCR analysis further indicated that the expression of some LEA genes would increase under simulated drought or different light conditions. This indicates that changes in temperature and light may alter lipid synthesis and accumulation by affecting the expression of related genes (Liu et al., 2023). 5.3 Potential links between altitude-specific stress and epigenetic change In high-altitude environments, low temperatures and strong ultraviolet rays are often present. These factors may affect the expression of genes related to oil synthesis, and thus also influence the final accumulation of oils. The expression changes of the LEA gene under drought and light variations also suggest that this regulatory process may involve epigenetic mechanisms, such as DNA methylation or histone modification. These mechanisms can help Camellia oleifera adapt to environmental stress and regulate oil accumulation simultaneously (Liu et al., 2023). Furthermore, the situation of multi-gene co-expression in high-oil Camellia oleifera also indicates that epigenetic regulation is likely to play an important role in this process (Wu et al., 2019). 6 Epigenetic Modifications Associated with Oil Traits 6.1 Differential DNA methylation regions (DMRs) related to fatty acid biosynthesis genes DNA methylation is an important epigenetic mode for regulating gene expression. Fatty acids are the main components of oils and fats, and their synthesis process is controlled by related genes. The methylation status of these genes will directly affect the accumulation of fats. Studies have found that different types of fatty acids, such as polyunsaturated fatty acids and short-chain fatty acids, can affect the methylation levels of these genes, thereby altering gene expression (Chung and Kim, 2024; Ediriweera and Sandamalika, 2024). In oil crops, key genes in the fatty acid synthesis pathway exhibit Differential DNA methylation regions (DMRs), which are closely related to the content and composition of oils. This also provides molecular-level evidence for explaining the differences in lipid properties between high-altitude and low-altitude Camellia oleifera.
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