Tree Genetics and Molecular Breeding 2025, Vol.15, No.3, 128-137 http://genbreedpublisher.com/index.php/tgmb 133 Figure 2 Cell types of roots, stems, leaves, and shoot apexes. The dotted lines indicate the absence of reported studies in woody plants (Adopted from Liang et al., 2023) 8 Case Study: Comparative Epigenomic Analysis of High- vs. Low-Altitude Camellia oleifera 8.1 Field sampling and phenotypic description of populations The research team selected some natural populations of Camellia oleifera from both high-altitude and low-altitude areas, systematically collected seed samples, and recorded phenotypic data such as the growth status of the plants, fruit size, and seed oil content. It was found that Camellia oleifera under different ecological environments showed significant differences in fruit development, oil accumulation and seed maturation. Camellia oleifera populations in high-altitude areas generally have higher oil content and more ideal fatty acid composition (Yang et al., 2024; Kong et al., 2025). 8.2 Key findings on methylation patterns and gene expression differences Through the analysis of whole-genome transcriptome and other multi-omics data, it was found that there were a large number of genes with significant expression differences in the early, middle and late stages of seed development in both high-oil and low-oil varieties. These genes were involved in multiple directions such as fatty acid synthesis, lipid accumulation and hormone signaling pathways (Wu et al., 2019; Yang et al., 2024). Among the varieties with high oil content, upstream genes such as HAD, EAR and KASI are continuously highly expressed, providing sufficient precursors for oleic acid synthesis. The expression level of the SAD gene is also relatively high, which is conducive to the accumulation of oleic acid. The expression of downstream genes such as FAD2 and FAD3 is relatively low, reducing the transformation and consumption of oleic acid (Wu et al., 2019; Yang et al., 2024). In addition, some transcription factors such as MADS-box and bHLH also show specific expression patterns in lipid synthesis regulation.
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