AgMYB1, an R2R3-MYB factor, plays a role in anthocyanin production and enhancement of antioxidant capacity in celery

Celery is rich in nutrients and cultivated worldwide. Anthocyanins are natural plant pigments with high antioxidant capabilities in the human diet. The accumulation of anthocyanins in celery results in the purple skin color of petioles. Here, an R2R3-MYB transcription factor (TFs), AgMYB1, was cloned from purple-skin celery. Phylogenetic analysis revealed that AgMYB1 belongs to the anthocyanin branch. Sequence alignment showed that AgMYB1 contains multiple anthocyanin-related motifs. Consistent with the activating role in anthocyanin production, AgMYB1 showed higher transcriptions in purple celery compared with non-purple celery. Transient expression of AgMYB1 in tobacco leaves promoted the accumulation of anthocyanins and produced red pigments in leaves. Heterologous expression of AgMYB1 in Arabidopsis activates anthocyanin production and generates dark-purple plants. The enhancement of anthocyanin biosynthetic genes transcripts and glycosylation capacities in transgenic Arabidopsis verified the activating roles of AgMYB1 at the gene and protein level, respectively. The antioxidant capacity of transgenic Arabidopsis was also increased compared to wild type Arabidopsis. Additionally, yeast two-hybrid assay proved that AgMYB1 interacted with bHLH TFs to regulate anthocyanin biosynthesis. Our results show that the overexpression of single R2R3-MYB gene, AgMYB1, without co-expression of other TFs, can improve anthocyanin production and antioxidant capacity in transgenic plants. This study presents new information for anthocyanin regulatory mechanisms in purple celery and provides a strategy for cultivating plants with high levels of anthocyanins.