Research Projects

Anthocyanin pigment synthesized in plant cells is universally popular for its health-benefits in addition to executing many functions inside plant cells, owing to its extraordinary antioxidant activity. Among the pigmented rice varieties, the Black Rice represent globally accessible highest source of anthocyanin (Abdel-Aal et al., 2006). The wide diversity of anthocyanin is credited to the evolution of stringent regulation of anthocyanin biosynthetic pathway (ABP), which permits tissue- and stage-specific localisation. However, ABP and its regulatory network is scantily known in rice—the staple food crop throughout. Although the MYB-bHLH-WDR (MBW) protein complex is well-established as the master-regulators (transcriptional) of ABP genes, further independent upstream regulators are essential to prevent redundant anthocyanin production. In this regard, epigenetic regulation, viz. DNA methylations and histone modifications can fine-tune gene expression to control tissue- and stage-specific pigmentation. MYB10 and MYB1 promoters occupied by methylated histones regulate ABP in apple and pear (Telias et al., 2011, Wang et al., 2013, El-Sharkawy et al., 2015, Bai et al., 2016). Even, MYB182 locus regulating ABP in poplar is epigenetically controlled by JMJ25 H3K9 demethylase (Fan et al., 2018). In Arabidopsis ABP genes, H3K4me3 deposition and IBM-led demethylation of SPA1/3/4 chromatin induced anthocyanin (Cai et al., 2019; Fan et al., 2024). Therefore, this project aims to find out how epigenetic regulation forms a critical ABP node in black rice. Anthocyanin is induced by diverse environmental cues, like light signal conveyed through ELONGATED HYPOCOTYL 5 (HY5). In light, COP1 (degrades HY5) is relocated to cytoplasm, to allow HY5 stabilize in the nucleus for anthocyanin synthesis. HY5 can induce ABP genes either by binding to the promoter of PAP1 or ABP genes or through miR858a activation to block the repressor MYBL2 or by repressing the MYBL2 promoter through histone modifications (Shin et al., 2013; Wang et al., 2016). Studies on HY5-mediated ABP regulation is sparse, reported only in eggplant, tomato, apple and pear (Jiang et al., 2016; Liu et al., 2018; An et al., 2017; Tao et al., 2018) besides Arabidopsis. There are no studies if the HY5 module works in anthocyanin-loaded black rice. Interestingly, my preliminary studies show HY5-binding cis elements (G box and Z box) in the promoter sites of ABP genes, depicted in Figure 1. The chief questions which linger are if HY5 will play similar master-regulatory role for anthocyanin production in black rice, if yes who are its reinforcement partners, and whether HY5 can mediate any epigenetic regulatory tuning for MBW/ABP players, as shown in Figure 2. Therefore, this project designed to deduce the epigenetic regulatory network of ABP in black rice will pave the way to develop cultivated rice varieties with anthocyanin content containing high nutrition value and exceptional stress mitigating ability.