Unraveling the regulatory network of flower coloration in soybean: Insights into roles of GmMYBA3 and GmMYBR1

Anthocyanins play crucial roles in pollen protection and pollinator attraction in flowering plants. However, the mechanisms underlying flower color determination and whether floral anthocyanin regulators participate in other processes remain largely unresolved in soybeans (Glycine max). In this study, we investigated the genetic components and mechanisms governing anthocyanin biosynthesis in soybean flowers. Molecular and genetic studies have characterized two antagonistic regulators, the positive activator GmMYBA3 and the negative repressor GmMYBR1, that modulate the gene expression of anthocyanin biosynthesis in soybean flowers. Further findings revealed a regulatory interplay between GmMYBA3 and GmMYBR1 bridged by GmTT8a, highlighting the complexity of anthocyanin regulation in different soybean organs. Exploration of additional soybean cultivars demonstrated the universality of GmMYBA3 and GmMYBR1 in regulating floral anthocyanin biosynthesis- related genes, with GmF3′5′H identified as a crucial determinant of white flower color. This study provides a molecular mechanism underlying soybean flower color determination, paving the way for the molecular modification of soybean flowers to probably enhance their resistance to abiotic stresses and attractiveness to pollinators.