Generating colorful carrot germplasm through metabolic engineering of betalains pigments

Abstract

Betalains are tyrosine-derived plant pigments exclusively found in the Caryophyllales order and some higher fungi and generally classified into two groups: red-violet betacyanins and yellow-orange betaxanthins. Betalains attract great scientific and economic interest because of their relatively simple biosynthesis pathway, attractive colors and health-promoting properties. Co-expressing two core genes BvCYP76AD1 and BvDODA1 with or without a glycosyltransferase gene MjcDOPA5GT allowed the engineering of carrot (an important taproot vegetable) to produce a palette of unique colors. The highest total betalains content, 943.2 μg·g⁻¹ DW, was obtained in carrot taproot transformed with p35S:RUBY which produces all of the necessary enzymes for betalains synthesis. Root-specific production of betalains slightly relieved tyrosine consumption revealing the possible bottleneck in betalains production. Furthermore, a unique volcano-like phenotype in carrot taproot cross-section was created by vascular cambium-specific production of betalains. The betalains-fortified carrot in this study is thus anticipated to be used as functional vegetable and colorful carrot germplasm in breeding to promote health.

Acknowledgements

The research was supported by the National Natural Science Foundation of China (32072563), Key Research and Development Projects of Ningxia Hui Autonomous Region (No.2022BBF02008), Priority Academic Program Development of Jiangsu Higher Education Institutions (Grant No. PAPD). We thank professor Yun-De Zhao and associate professor Yu-Bing He for sharing the pDR5:RUBY plasmid.

Author contributions

A-S.X. and Y-J.D. initiated and designed the research. Y-J.D. and A-Q.D. performed the experiments. Y-J.D. and R-R.Z. analysed the data. Y-H.W., H.L., and Z-S.X. contributed reagents/materials/analysis tools. Y-J.D. wrote the paper. A-S.X. revised the paper.

Data availability

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.

Conflict of interest

None declared.

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