Scientists have pinpointed the genetic change behind purple leaves in Chinese cabbage, a leafy form of Brassica rapa prized across East Asia. In a study published in Plant Cell Reports, a team working with the non-heading Chinese cabbage inbred line P-KC1 showed that a single dominant gene, BraA3.AP2, controls the striking pigment trait. The finding traces purple leaf coloration to a specific molecular module that boosts anthocyanin, the natural plant pigments also found in berries and red cabbage that are considered beneficial to human health.
The purple phenotype is not spread evenly through the plant. Anthocyanins accumulate specifically in the adaxial epidermis, the upper skin layer of cotyledons and rosette leaves, giving the foliage its distinctive color. Classical genetic analysis of the trait revealed that it is controlled by a single dominant locus, meaning one copy of the responsible variant is enough to produce purple leaves in offspring that inherit it.
Expression analysis in Brassica rapa, together with genetic transformation experiments in Arabidopsis thaliana, a widely used laboratory plant, demonstrated that BraA3.AP2 expression positively correlates with anthocyanin accumulation in leaves.
The team identified a 1,647-base-pair insertion in the BraA3.AP2 promoter. This inserted sequence functions as a leaf-specific transcriptional enhancer, elevating the gene’s activity in leaf tissues. That tissue specificity explains why the pigment builds up in leaves rather than throughout the plant.
Having established where BraA3.AP2 acts, the researchers probed how it works at the molecular level. From there, it directly binds to and activates the promoter of BraA7.MYB2, a gene encoding a key transcriptional activator of anthocyanin biosynthesis.
The interaction does not stop at DNA-level control. The team also demonstrated that BraA3.AP2 physically interacts with the BraA7.MYB2 protein itself. This dual mechanism, transcriptional activation of the MYB2 gene combined with direct protein-to-protein partnership, defines what the authors describe as a novel BraA3.AP2–BraA7.MYB2 regulatory module that enhances anthocyanin biosynthesis in the leaves.
The study, authored by Xiaolong Zhang, Bin Feng and colleagues including Haitao Li, appeared in Volume 45 of Plant Cell Reports as article number 349, with publication dated 29 October 2026.
Beyond basic plant biology, the results carry practical weight for crop improvement. Because the purple trait is dominant and tied to a single identifiable locus with a defined enhancer insertion, it offers breeders a clear molecular target. The authors suggest the BraA3.AP2–BraA7.MYB2 module could serve as a potential target for breeding anthocyanin-enriched Brassica rapa varieties, leafy vegetables whose deep purple color would signal a higher content of pigments valued for their health-associated properties.
Subject of Research: Genetic regulation of anthocyanin-based purple leaf coloration in Brassica rapa
Article Title: BraA3.AP2 regulates purple leaf by transcriptional activation and interaction of BraA7.MYB2 in Brassica rapa
Article References: Zhang, X., Feng, B., Wang, X., Luo, M., Peng, S., Zhang, B., Li, Y., Zhang, H., Hu, J., Yuan, W., & Li, H. (2026). BraA3.AP2 regulates purple leaf by transcriptional activation and interaction of BraA7.MYB2 in Brassica rapa. Plant Cell Reports, 45(11), Article 349. https://doi.org/10.1007/s00299-026-04031-0
Image Credits: AI Generated
DOI: 10.1007/s00299-026-04031-0
Keywords: Brassica rapa, anthocyanins, purple leaves, BraA3.AP2, BraA7.MYB2, transcription factor, promoter insertion, map-based cloning, Chinese cabbage, plant genetics, enhancer, breeding
News Source: Juliet Wilcox. (October 29, 2026). Purple Leaf Gene Found in Chinese Cabbage Offers Route to Healthier Greens. Scienmag.
