Abstract: Hongcaitai (Brassica rapa) is a vegetable that accumulates anthocyanins in both floral stems and leaf petioles. To understand the mechanism underlying the regulation of anthocyanin biosynthesis in B. rapa, anthocyanin accumulation and expression patterns of anthocyanin biosynthesis genes in seedlings of Hongcaitai were investigated. Anthocyanin content in epidermal tissues of petioles were significantly higher than those in leaves with excised mid-veins. Expression levels of all anthocyanin biosynthesis pathway genes were significantly higher in epidermal tissues of petioles than those detected in either endodermal tissues of petioles or in leaves, suggesting that anthocyanin biosynthesis was regulated at the transcriptional level. Transcripts of BrMYBA1 were exclusively expressed in the petiole epidermis; whereas, transcripts of BrbHLH1 and BrWD40 were detected in both leaves and petiole epidermal tissues. This suggests that activation of BrMYBA1 was likely responsible for anthocyanin pigmentation in Hongcaitai. Following cold treatment, seedlings demonstrated increased accumulation of anthocyanins in petiole epidermal tissues, while the transcription of anthocyanin pathway genes was reduced in petiole epidermal tissues.