Transcription activator, when associated with BHLH12/MYC1, EGL3, or GL3. Promotes the synthesis of phenylpropanoid-derived compounds such as anthocyanins. Interacts with BHLH12/MYC1, BHLH1/GL3/MYC6, BHLH2/EGL3/MYC146, and BHLH42/TT8. Expressed only in leaves and siliques. By sucrose, nitrogen deficiency, ethylene, UV light and drought.