Tree Genetics and Molecular Breeding 2025, Vol.15, No.3, 98-107 http://genbreedpublisher.com/index.php/tgmb 100 R2R3-MYB family play a leading role, responsible for initiating or inhibiting the expression of anthocyanidin-related genes; While bHLH and WD40 help MYB function better (Zhao et al., 2019; Peng et al., 2020; Karppinen et al., 2021). In addition, some MYB transcription factors may also be related to hormone signals or stress responses, further refining the regulation of anthocyanin synthesis (Pratyusha and Sarada, 2022). Figure 1 Immunofluorescence localization of auxin in the (a) longitudinal and (b) transverse sections of flesh segments (Adopted from Fu et al., 2025) Image caption: The bayberry variety used for the immunofluorescence localization analysis was ‘Biqi’, and all scale bars were set to 200 μm. In (a), the dashed line indicates a longitudinal section of a single flesh segment, where the auxin fluorescence signals are enriched at the top and side walls of the flesh segment, forming a continuous linear distribution along the contour marked by the dashed line. In (b), the arrow indicates the central vascular bundle within the cross-section of the flesh segment, where the enrichment of auxin fluorescence signals is observed (Adopted from Fu et al., 2025) 4 Advances in Cloning of Anthocyanin Biosynthetic Genes in Morella rubra 4.1 Gene discovery strategies and transcriptome profiling In China, researchers mainly identified the genes related to anthocyanin synthesis in Morella rubra through transcriptome sequencing and comparative analysis. They conducted transcriptome sequencing on fruits of different colors (such as white, red, and deep purple-red) and at different developmental stages, and screened out some structural genes and regulatory genes that are closely related to anthocyanin accumulation. For instance, a study identified 60 genes of the WD40 family using the RNA-Seq database and, by comparing their expression levels with anthocyanin contents, identified some of them as key regulatory factors (Liu et al., 2013a; Cao et al., 2021). In addition, by comparing the gene expression of red and white fruits, a MYB transcription factor called MrMYB9 was also discovered, which promotes anthocyanin synthesis (Li et al., 2023). 4.2 Isolation and characterization of structural genes At present, the structural genes that have been identified in Morella rubra mainly include: CHS, CHI, F3H, F3’H, DFR, ANS and UFGT (Liu et al., 2013b). The expression levels of these genes vary in different fruit colors and
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