Investigating Carrot Colors to Produce Healthier Crops

Authors: Simon, Philipp

Submitted to: Scientia Global
Publication Type: Literature Review
Publication Acceptance Date: 10/23/2019
Publication Date: 10/24/2019
Citation: Simon, P.W. 2019. Investigating Carrot Colors to Produce Healthier Crops . Scientia Global. https://doi.org/10.33548/SCIENTIA433.
DOI: https://doi.org/10.33548/SCIENTIA433

Interpretive Summary: Orange carrots are familiar to consumers around the world, but were only first described around 500 years ago. Purple and yellow were the first colors of carrots during its domestication history, reported 1100 years ago. To add to the rainbow of carrot colors, red and white carrots were developed within the last several hundred years. The pigments responsible for carrot colors are carotenoids, for orange, yellow, and red carrots, and anthocyanins, for purple carrots. The bright colors of carrots are an important visual cue to stimulate consumer interest and increase consumption, and consumption of brightly colored carrots has important positive nutritional consequences. Most important of these are the orange carotenoids which are sources of vitamin A. The red, yellow, and purple pigments also provide key nutrients as antioxidants contributing to eye health and to reduced incidence of cardiovascular disease and certain forms of cancer. Carrot colors have also attracted an interest in the scientific research community as they provide insights into the historical development and domestication of carrot as a root crop, they provide a foundation for a better understanding of the molecular and biochemical mechanisms underlying carotenoid and anthocyanin biosynthesis, and they are useful as a toolbox for nutritionists to study pigments in whole foods. The sequencing of the carrot genome has been a recent significant stimulus in providing insights in the development of high-pigment carrots and this story is only beginning to unfold.

Technical Abstract: Through mapping, re-sequencing and transcriptome analysis of carrot we identified a candidate gene controlling carotenoid accumulation in the carrot root that is an important domestication trait, the foundation to the orange color of modern carrots, and a model for the discovery of regulatory mechanisms underlying carotenoid accumulation in plants. Transcriptome analysis combined with genome-wide association demonstrated that a region on chromosome 3 also controls carotenoid accumulation in carrot and contains the OR gene, a gene that has been associated with carotenoids in other crops. Using linkage analysis in a carrot F2 mapping population segregating for root and leaf anthocyanin pigmentation, we identified two regions in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas leaf pigmentation segregated as a single dominant gene and mapped to one of these “root pigmentation” regions. A cluster of six MYB transcription factors awas ssociated with anthocyanin biosynthesis regulation. Comparative transcriptome analysis in pigmented and non-pigmented root and leaf tissues indicated that expression of MYB1 was associated with anthocyanin pigmentation in both root and leaf tissues, whereas MYB3 was only associated with leaf pigmentation. MYB2, a gene that has been previously suggested to be a key regulator of the anthocyanin pathway in carrot was not consistently associated with either tissue. DcMYB7, and two cytochrome CYP450 genes were associated with the presence and concentration of root anthocyanins.