Beyond Purple Tomatoes: Combined Strategies Targeting Anthocyanins to Generate Crimson, Magenta, and Indigo Fruit

Eugenio Butelli,Lionel Hill,Cathie Martin,Katharina Bulling

doi:10.3390/horticulturae7090327

Eugenio Butelli, Lionel Hill + Show 2 more

Open Access

https://doi.org/10.3390/horticulturae7090327

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Journal: Horticulturae	Publication Date: Sep 21, 2021
Citations: 10	License type: CC BY 4.0

Affiliation: John Innes Centre, Danone (Netherlands)

Abstract

The range of colours of many flowers and fruits is largely due to variations in the types of anthocyanins produced. The degree of hydroxylation on the B-ring affects the hue of these pigments, causing a shift from the orange end of the visible spectrum to the blue end. Besides colour, this modification can also affect other properties of anthocyanins, including the ability to protect the plant against different stresses or, when included in the human diet, to provide benefits for disease prevention. The level of hydroxylation of the B-ring is determined by the activity of two key hydroxylases, F3′H and F3′5′H, and by the substrate preference of DFR, an enzyme acting downstream in the biosynthetic pathway. We show that, in tomato, a strategy based on fruit-specific engineering of three regulatory genes (AmDel, AmRos1, AtMYB12) and a single biosynthetic gene (AmDFR), together with the availability of a specific mutation (f3′5′h), results in the generation of three different varieties producing high levels of anthocyanins with different levels of hydroxylation. These tomatoes show distinctive colours and mimic the classes of anthocyanins found in natural berries, thus providing unique near-isogenic material for different studies.

Highlights

Anthocyanins are strikingly vibrant natural plant pigments responsible for a wide range of colour variation—from orange to blue—in many flowers, fruit, and vegetables
In tomato, tissue-specific expression of two regulatory genes, AmDel and AmRos1, can induce the accumulation of high levels of D3 anthocyanins in tomato fruit [18]
We show that combining genetic engineering with the availability of natural mutants can expand the chemical diversity of anthocyanins to generate unique tomato lines producing P1, C2, or D3-based anthocyanins

Summary

Introduction

Anthocyanins are strikingly vibrant natural plant pigments responsible for a wide range of colour variation—from orange to blue—in many flowers, fruit, and vegetables. In addition to their well-documented physiological roles in plant life, which include attraction of pollinators and seed dispersers and protection against biotic and abiotic stresses [1], dietary anthocyanins have been linked to a wide range of health benefits and protection against the most prevalent chronic human diseases (cardiovascular disease, cancer, diabetes, obesity, and neurological disorders) [2,3,4]. The chemical diversity and complexity of anthocyanins is a major obstacle. One thousand different naturally occurring compounds have been reported, whose structures differ in the combinations of sugar units, methoxyl groups, aliphatic and aromatic acyl groups decorating the basic structure of anthocyanins: a C6-C3-C6 skeleton structure consisting of two aromatic rings (A and B) and a central heterocyclic oxygen ring (C) with a positive charge (Figure 1), known as a flavylium cation [9]

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