Journal of Tea Science Research, 2024, Vol.14, No.1, 64-78 http://hortherbpublisher.com/index.php/jtsr 71 et al., 2019). This study demonstrated that different Camellia species exhibit distinct patterns of gene flow, which are crucial for maintaining genetic diversity and facilitating adaptation to varying environmental conditions. Genetic variation plays a pivotal role in the adaptive evolution of Camellia species. Comparative genomics and transcriptomic analyses have shown that Camellia plants have undergone whole genome duplication events, leading to the expansion of transcription factor families associated with stress resistance and secondary metabolism (Wu et al., 2022). This genetic variation enables Camellia species to adapt to diverse environmental conditions and enhances their resilience to biotic and abiotic stresses. Furthermore, the presence of polymorphic ribosomal DNA (rDNA) in Camellia species suggests a mixture of concerted and birth-and-death evolution, contributing to the genetic diversity and potential adaptive functions of rRNA pseudogenes (Zhang et al., 2020). 4.3 Comparative genomics Comparative genomics involves analyzing the genomes of different species to identify conserved and divergent genetic elements, providing insights into evolutionary relationships and functional adaptations. Comparative genomics studies have provided insights into the evolutionary history and adaptive mechanisms of the Camellia genus. For example, the comparative analysis of chloroplast genomes among different Camellia species has shed light on their phylogenetic relationships and evolutionary routes (Li et al., 2019). These studies have revealed that Camellia species exhibit unique evolutionary patterns compared to other related genera, highlighting the importance of chloroplast genome sequences in understanding the genetic basis of adaptation and evolution. Comparative genomics has also uncovered significant findings related to the adaptive evolution of Camellia species. The analysis of transcriptomes from 116 Camellia plants revealed a recent whole genome duplication event and the expansion of transcription factor families associated with stress resistance and secondary metabolism (Wu et al., 2022). These genomic insights have provided a deeper understanding of the molecular mechanisms underlying the adaptation of Camellia species to their environments. Additionally, the identification of lineage-specific genes in Camellia sinensis has highlighted the role of gene duplication in generating new functions and adaptive traits (Figure 3) (Zhao and Ma, 2019). These findings underscore the importance of comparative genomics in elucidating the evolutionary history and adaptive strategies of the Camelliagenus. Figure 3 Analyze and compare the structural characteristics of Camellia-specific genes (CSGs) and evolutionarily conserved genes (ECs) (Adopted from Zhao and Ma, 2021) Image caption: (A) Box-plot comparisons of gene length. (B) protein length. (C) exon size. (D) intron size. (E) exon number in per gene. (F) GCs content. (G) isoelectric point. The analysis of Figure 3 indicates that CSGs are generally shorter, with fewer and smaller exons and introns, but have higher GC content and isoelectric points compared to ECs. These structural differences suggest that CSGs are simpler and potentially more specialized, reflecting their specific evolutionary roles inCamellia species (Adapted from Zhao and Ma, 2021)
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