The candidate gene SibHLHA regulates anthocyanin-driven purple pigmentation in Sesamum indicum flowers

Anthocyanins not only serve as critical pigments determining floral hues but also play essential roles in attracting insects for pollination, feeding animals and mitigating abiotic stress. However, the molecular mechanisms underlying the regulation of flower color in sesame has not yet been reported. In this study, an F₂ population was constructed by crossing 'Ganzhi 9' (purple-flowered) with 'BS377' (white-flowered). Genetic analysis revealed that purple flower is controlled by a single locus named as SiFC (Sesamum indicum flower color). Using the BSA-seq approach, SiFC was preliminarily identified on chromosome 6, which was further mapped to a 473 kb interval using Kompetitive Allele Specific PCR (KASP) marker analysis. Moreover, functional annotation, expression profiling, and sequence analyses confirmed that the SibHLHA (Sesame10992) was the most likely candidate gene for SiFC. In addition, SibHLHA, highly homologous to AtTT8 (a key regulator in the anthocyanin synthesis pathway), was found to interact with WER-like or TTG1 proteins, enhancing anthocyanin accumulation in tobacco leaves. Furthermore, an SNP in the second exon of Sibhlha (BS377 variant) was found to alter the encoding amino acids, which affected Sibhlha binding to MYB protein and showed low anthocyanin in tobacco leaves compared with SibHLHA binding with WER-like or TTG1 proteins. These findings not only deepen our understanding of the molecular mechanisms controlling sesame corolla color, but also provide valuable insights for developing ornamental and consumable sesame varieties.