Carrot Anthocyanins Genetics and Genomics: Status and Perspectives to Improve Its Application for the Food Colorant Industry

Abstract

Purple or black carrots (Daucus carota ssp. sativus var. atrorubens Alef) are characterized by their dark purple- to black-colored roots, owing their appearance to high anthocyanin concentrations. In recent years, there has been increasing interest in the use of black carrot anthocyanins as natural food dyes. Black carrot roots contain large quantities of mono-acylated anthocyanins, which impart a measure of heat-, light- and pH-stability, enhancing the color-stability of food products over their shelf-life. The genetic pathway controlling anthocyanin biosynthesis appears well conserved among land plants; however, different variants of anthocyanin-related genes between cultivars results in tissue-specific accumulations of purple pigments. Thus, broad genetic variations of anthocyanin profile, and tissue-specific distributions in carrot tissues and organs, can be observed, and the ratio of acylated to non-acylated anthocyanins varies significantly in the purple carrot germplasm. Additionally, anthocyanins synthesis can also be influenced by a wide range of external factors, such as abiotic stressors and/or chemical elicitors, directly affecting the anthocyanin yield and stability potential in food and beverage applications. In this study, we critically review and discuss the current knowledge on anthocyanin diversity, genetics and the molecular mechanisms controlling anthocyanin accumulation in carrots. We also provide a view of the current knowledge gaps and advancement needs as regards developing and applying innovative molecular tools to improve the yield, product performance and stability of carrot anthocyanin for use as a natural food colorant.

Bioactive Compounds and Antioxidant Capacity in Anthocyanin-Rich Carrots: A Comparison between the Black Carrot and the Apulian Landrace “Polignano” Carrot

“…The phytochemical composition, particularly in relation to anthocyanins, has been reported in detail [ 8 , 25 , 26 , 27 ]. At the molecular level, the biosynthetic pathways leading to anthocyanins have been also studied in the black carrot [ 7 , 28 ].…”

“…In most purple-rooted species, anthocyanins are expressed in the epidermal layer of the root, but also in the cortex (phloem), and in the xylem (core) tissues, presenting different pigmentation patterns across these tissues [ 7 ].…”

Anthocyanin Pigments: Beyond Aesthetics

“…The growing demand for natural alternatives to food colorants and the increased awareness of the environmental hazards of synthetic analogues have accelerated research initiatives towards this goal. The global demand for natural colorants has increased in the past decade [ 84 ]. This had forced several food colorant companies to shift to natural food colorants.…”

A Roadmap to Modulated Anthocyanin Compositions in Carrots

“…Since the interest of black carrots for producing anthocyanin pigments has become increasingly high, there has also been an interest in identifying the structural and regulatory genes associated with anthocyanin biosynthesis in black carrots. In this review we will only include and refer to carrot anthocyanin structural and regulatory genes included in the recent review by Iorizzo et al [ 28 ]. Here they integrated the structural genes from data of eight independent studies [ 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 ] and the regulatory genes from data of six independent studies [ 64 , 65 , 68 , 70 , 71 , 72 ].…”

“…Since the interest in cultivation of black carrots for production of anthocyanins has become increasingly high, there has also been an interest in identifying the structural and regulatory genes associated with anthocyanin biosynthesis in black carrots. Along with the publication of the carrot genome sequence by Xu et al [ 26 ] and the high-quality sequence also assembled at the chromosome level by Iorizzo et al [ 27 ], huge progress in the identification of genes involved in anthocyanin biosynthesis and genes involved in the secondary modifications i.e., glycosylation and acylation has been made [ 28 ]. Given this information it is now possible to attempt to modulate anthocyanin compositions in black carrots through genetic modifications.…”