Identification and characterization of C-glycosyltransferase (CGT) gene family associated with flavonoid-mediated shelf-life extension in pearl millet flour.

Pearl millet is a vital dryland, nutrient-rich C4 crop with significant potential to reduce hidden hunger among vulnerable groups. However, its wider commercialization is limited by the short shelf life of its flour. Several endogenous compounds, particularly antioxidant flavonoids, are associated with reduced rancidity. Among these, C-glycosyl flavonoids are considered important contributors to the enhanced shelf life of flour. C-glycosyltransferases (CGTs) encode proteins containing the UDP-glycosyl transferase domain and are predicted to play a regulatory role in flavonoid glycosylation. However, a detailed study on the quality of pearl millet flour is lacking. In this study, 32 PgCGT genes were identified and mapped to all the chromosomes except chromosome 3. Most of the CGT genes (18) are predicted to be located in chloroplasts. Gene structure analysis showed that most (25) genes had only one exon. Motif analysis identified conserved motifs within the CGT gene family in pearl millet. Comparative synteny analysis across cereal genomes suggested that purifying selection likely shaped the evolution of this gene family, with 15, 18, 20, and 15 conserved orthologs identified in rice, sorghum, foxtail millet, and maize, respectively. Promoter analysis identified cis-regulatory elements predicted to be associated with seed-specific regulation and endosperm-specific expression. The low-rancid genotype DS-SP-15 showed significantly higher flavonoid content at day 0 (131.44 mg QE/100 g) and day 10 (141.88 mg QE/100 g) than the high-rancid genotype DS-SP-9, which recorded 107.04 mg QE/100 g and 117.17 mg QE/100 g at the respective time points. The observed gene expression differences in contrasting inbred lines at various times suggest a potential role in flour shelf life in pearl millet. This study provides a comprehensive characterization of the PgCGT gene family and highlights possible functional divergence among its members. These results provide a solid foundation for future functional validation and targeted genome editing to improve grain quality and extend the shelf life of pearl millet flour.