Kohlrabi (Brassica oleracea var. gongylodes L.) is an important dietary vegetable cultivated and consumed widely for the round swollen stem. Purple kohlrabi shows abundant anthocyanin accumulation in the leaf and swollen stem. Here, different kinds of anthocyanins were separated and identified from the purple kohlrabi cultivar (Kolibri) by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. In order to study the molecular mechanism of anthocyanin biosynthesis in purple kohlrabi, the expression of anthocyanin biosynthetic genes and regulatory genes in purple kohlrabi and a green cultivar (Winner) was examined by quantitative PCR. In comparison with the colorless parts in the two cultivars, most of the anthocyanin biosynthetic genes and two transcription factors were drastically upregulated in the purple tissues. To study the effects of light shed on the anthocyanin accumulation of kohlrabi, total anthocyanin contents and transcripts of associated genes were analyzed in sprouts of both cultivars grown under light and dark conditions.

Tumorous stem mustard (Brassica juncea var. tumida Tsen et Lee) is an economically and nutritionally important dietary vegetable in Asian countries. Purple tumorous stem mustard contains inflated tumorous stem and abundant anthocyanin accumulation in leaves. Here, 20 anthocyanins were separated and identified from the purple tumorous stem mustard by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS). In order to investigate the regulatory anthocyanin production in purple tumorous stem mustard, the expression of anthocyanin biosynthetic and regulatory genes in leaves from purple and green cultivars were examined. Regulatory gene BjTT8 and all biosynthetic genes were dramatically upregulated in the purple variety. Moreover, the transcript level of BjTT8 and all structural genes, except BjPAL, were all significantly higher in light-treated sprouts than in the dark. These results indicate that transcriptional activation of BjTT8 is associated with upregulation of most anthocyanin biosynthetic genes, to produce anthocyanins in purple tumorous stem mustard.

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