International Journal of Molecular Evolution and Biodiversity, 2025, Vol.15, No.2, 111-123 http://ecoevopublisher.com/index.php/ijmeb 113 Figure 1 Construction of vectors for targetingBnaAGhomologous genes (Adopted from Song et al., 2023) Image caption: (A) NJ tree of BnaAG homologous genes in B. napus and A. thaliana; The red stars represent the BnaAG homologs of B. napus closely related to the AGgene in A. thaliana; (B) Gene structure, conserved domain, and distribution of sgRNA1 and sgRNA2 targeting four homologous genes of BnaAG; The black line represents introns, and the black boxes represent the exon; The red arrows indicate the location of sgRNA targets on the exon, and the orange and blue boxes represent MADS-box and K-box domains, respectively; (C) Sequence information of two sgRNA, PAM is indicated in red (Adopted from Song et al., 2023) 3.3 Developmental regulation of MYB and bHLH families When the temperature drops sharply, multiple members of the bHLH family can be rapidly activated, and their expression levels in cold-resistant rapeseed varieties can be increased to more than 15 times the original in a short period of time (Waseem et al., 2024). The complementary MYB transcription factors show greater flexibility in regulatory strategies. For example, BnMRD107 can synchronously regulate osmotic stress-related genes and participate in the interactive regulation of multiple hormone signals (Li et al., 2021). These two transcription factor families jointly construct a highly plastic signal regulatory network that can dynamically adjust its regulatory strategy according to different developmental stages of plants or changes in the external environment: the seedling stage is mainly based on cell proliferation, while the reproductive growth period focuses on the regulation of floral organ differentiation and stress response. 4 Epigenetic Modifications inBrassica napus 4.1 DNA methylation and gene silencing High-density methylation in the transposable element region forms a molecular barrier that effectively inhibits the expression of neighboring genes (Xiao et al., 2023). This silencing mechanism is particularly prominent in allopolyploid genomes. When the two parental genomes merge, DNA methylation is like a shrewd referee, selectively "silencing" the rRNA genes of a certain ancestral genome (Zj and Pikaard, 1997). The methylation level of the promoter region shows an interesting correlation with the gene expression: mild methylation may promote expression, while excessive methylation leads to gene silencing (Hu et al., 2023). This dynamic balance enables plants to flexibly respond to environmental challenges (Figure 2).
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