Genomics and Applied Biology 2024, Vol.15, No.4, 200-211 http://bioscipublisher.com/index.php/gab 203 degree of conservation in gene order. This finding suggests that significant chromosomal rearrangements and divergence have occurred (Monna et al., 2006; Shi et al., 2022). 4.3 Gene duplication and divergence Gene duplication events have been a significant driving force in the expansion and functional diversification of the R2R3-MYB gene family in rice. The existence of multiple allelic and structural variations within these genes indicates a history of gene duplication followed by divergence. For example, the Rc locus, a key regulatory gene in the anthocyanin biosynthetic pathway, exhibits a 14 bp deletion in the Purpleputtu rice variety, which is a characteristic feature of modern white pericarp rice cultivars (Lachagari et al., 2019; Khan et al., 2021). These observations illustrate the evolutionary dynamics and adaptive significance of gene duplication in the R2R3-MYB gene family, as well as the importance of considering similar variations. 5 Expression Profiling of R2R3-MYBGenes 5.1 Expression patterns in different tissues The expression patterns of R2R3-MYB genes in diverse tissues of colored rice have been the subject of extensive investigation. R2R3-MYB TFs have been demonstrated to play a pivotal role in a multitude of biological processes, including tissue development. In rice, the Os2R_MYBgenes exhibit tissue-specific expression patterns, which are essential for understanding their functional roles in plant growth and development (Dai et al., 2012). For instance, Kang et al. (2022) identified 190 MYB TFs, including 99 R2R3-MYBs, and discovered that these genes are unevenly distributed across the 12 chromosomes of rice. The analysis demonstrated notable discrepancies in the expression levels of the Os2R_MYB gene across diverse tissues and developmental stages (Figure 1). It also revealed that specific Os2R_MYBs are uniquely expressed in particular tissues, suggesting their specialized functions within those tissues. Figure 1 The relative expression level of Os2R_MYBgenes in various tissues and growth stages (Adopted from Kang et al, 2022) Image caption: Lower expression is represented with dark blue; higher expression is represented with red; Leaf-blade, vegetative leaf-blade; Leaf-sheath, vegetative leaf-sheath; Root, vegetative root; Stem, reproductive stem; Inflorescence, 0.6-1 mm; Anther, 0.7-1 mm; Pistil, 5-10 cm; Ovary, 3 DAF; Embryo, 10 DAF; Endosperm, 42 DAF (Adopted from Kang et al, 2022)
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