Rice Genomics and Genetics 2024, Vol.15, No.6, 265-276 http://cropscipublisher.com/index.php/rgg 271 5.2 Interaction with other TFs and co-regulators R2R3-MYB TFs frequently act in conjunction with other TFs and co-regulators to regulate anthocyanin biosynthesis. In petunia, the R2R3-MYB factors DEEP PURPLE (DPL) and PURPLE HAZE (PHZ) interact with the basic helix-loop-helix (bHLH) factor ANTHOCYANIN1 (AN1) and the WD-repeat protein AN11 to regulate anthocyanin production in vegetative tissues (Albert et al., 2011). Similarly, in Chinese tallow, the R2R3-MYB factor SsMYB1 interacts with the bHLH protein SsbHLH1 to enhance the transcription of anthocyanin biosynthetic genes, thereby promoting anthocyanin accumulation (Chen et al., 2021). These interactions highlight the significance of transcriptional complexes in the precise regulation of anthocyanin biosynthesis. 5.3 Post-translational modifications (PTMs) and stability of R2R3-MYB proteins PTMs are of great consequence for the stability and activity of R2R3-MYB proteins. These modifications can include phosphorylation, ubiquitination, and sumoylation, which can either enhance or repress the activity of MYB proteins. For example, the stability of the OsC1 protein in rice, an R2R3-MYB TF, is of critical importance for its role in regulating anthocyanin biosynthesis and oxidative stress tolerance (Upadhyaya et al., 2021). While the specific PTMs of OsC1 were not delineated, the general significance of PTMs in regulating MYB protein function is well documented in the literature (Yang et al., 2022). 5.4 Epigenetic modifications influencing R2R3-MYBgene expression Epigenetic modifications, including DNA methylation and histone modifications, have been demonstrated to exert a considerable influence on the expression of R2R3-MYBgenes. In Capsicum annuum, the insertion of a non-long terminal repeat retrotransposon in the promoter region of the CaAn2 gene, an R2R3-MYB TF, results in its activation by recruiting TFs to the 3' untranslated region of the retrotransposon (Jung et al., 2019). This example demonstrates how epigenetic alterations can result in the activation of MYB genes and subsequent anthocyanin biosynthesis. Furthermore, natural variations in the promoter regions of R2R3-MYBgenes can result in differential expression and anthocyanin accumulation in a range of plant species (Yang et al., 2022). In conclusion, the regulation of R2R3-MYBgenes and their role in anthocyanin biosynthesis is a complex process involving signal transduction pathways, interactions with other TFs, PTMs, and epigenetic modifications. These mechanisms collectively ensure the precise control of anthocyanin production in response to environmental and developmental cues. 6 Significance of Anthocyanin Modulation in Dark Purple Rice 6.1 Role of anthocyanins in stress tolerance The anthocyanins present in dark purple rice play a pivotal role in enhancing the stress tolerance of this particular variety. The R2R3-MYB TFs, such as OsC1, are of great importance in the regulation of the anthocyanin biosynthesis pathway (ABP) (Lin et al., 2022). The overexpression of OsC1 in rice has been demonstrated to elevate anthocyanin levels, which subsequently enhances the plant's capacity to withstand oxidative stress by reducing the concentration of reactive oxygen species (ROS). This results in enhanced photosynthetic efficiency and reduced membrane damage under stress conditions, thereby strengthening the plant's overall resilience to oxidative stress (Upadhyaya et al., 2021; Yang et al., 2022). 6.2 Impact on plant growth and development The influence of anthocyanins on plant growth and development is a significant area of research. The presence of these pigments, which are regulated by MYB TFs, contributes to the visual appeal and nutritional quality of the plant. The accumulation of anthocyanins, particularly cyanidin 3-glucoside, in dark purple rice is associated with the expression of late ABP genes during the panicle stage. This not only enhances the plant's aesthetic value but also supports its growth by improving photosynthetic efficiency and reducing oxidative damage (Feng et al., 2018; Upadhyaya et al., 2021; Yan et al., 2021; Kavas et al., 2022). 6.3 Contribution to reproductive success and seed quality Anthocyanins play a role in the reproductive success and seed quality of dark purple rice. The pigmentation provided by these compounds attracts pollinators and seed dispersers, which is essential for the plant's
RkJQdWJsaXNoZXIy MjQ4ODYzNA==