Abstract: The OsTTG1 gene encodes a WD40 domain repeat protein, with its knockout in Oryza sativa L. known to affect anthocyanin accumulation. However, whether this gene affects other traits remains unclear. In this study, OsTTG1 was overexpressed in the Arabidopsis thaliana (L.) Heynh. ttg1 mutant. Results showed that overexpression of OsTTG1 (OsTTG1-OE) restored anthocyanin accumulation in leaves and stalks, produced dark brown seeds, and promoted epidermal hair development on leaves, stalks, and calyces. In contrast, the ttg1 mutant exhibited flowering 3–5 d earlier than both the Col-0 and OsTTG1-OE strains, while no significant differences in flowering time were observed between Col-0 and OsTTG1-OE. RNA-seq analysis of differentially expressed genes (DEGs) between OsTTG1-OE and ttg1 at various developmental stages revealed key gene clusters potentially associated with anthocyanin synthesis (MKK9, CYP75B1, TT8, GSTF12, DFR, F3H, CHS, and LDOX), epidermal hair formation (SPL15, TCL1, ETC2, SPL4, SPL13A, ETC3, and GIS), and flowering regulation (FLC, FT, AGL19, HDA5, and LHY). These findings provide an important theoretical basis and reference for understanding the function of OsTTG1 in O. sativa.