Alteration of flavonoid pigmentation patterns during domestication of food crops

Abstract

Flavonoids are plant pigments that provide health benefits for human and animal consumers. Understanding why domesticated crops have altered pigmentation patterns and unraveling the molecular/genetic mechanisms that underlie this will facilitate the breeding of new (healthier) varieties. We present an overview of changes in flavonoid pigmentation patterns that have occurred during crop domestication and, where possible, link them to the molecular changes that brought about the new phenotypes. We consider species that lost flavonoid pigmentation in the edible part of the plant at some point during domestication (like cereals). We also consider the converse situation, for example eggplant (aubergine), which instead gained strong anthocyanin accumulation in the skin of the fruit during domestication, and some varieties of citrus and apple that acquired anthocyanins in the fruit flesh. Interestingly, the genes responsible for such changes are sometimes closely linked to, or have pleiotropic effects on, important domestication genes, suggesting accidental and perhaps inevitable changes of anthocyanin patterning during domestication. In other cases, flavonoid pigmentation patterns in domesticated crops are the result of cultural preferences, with examples being found in varieties of citrus, barley, wheat, and maize. Finally, and more recently, in some species, anthocyanins seem to have been the direct target of selection in a second wave of domestication that followed the introduction of industrial food processing.

Domestication of Crop Metabolomes: Desired and Unintended Consequences

“…Other examples of tracking metabolic variation include longstanding breeding for (i) reduced bitterness in potato (S. tuberosum), tomato, and cucumber [79], (ii) modified acidity in sweet melon (Cucumis melo var. cantalupo) [80], apple (Malus domestica) [81], (iii) modified sweetness in watermelon (Citrullus lanatus) [82], (iv) attractive color in citrus [83], melon [77], tomato [54], maize, rice, barley, soybean (Glycine max), grape (Vitis vinifera), apple, and common bean [84], (v) starchiness in rice [47,85], and (vi) aroma in a wide range of crops including tomato, pepper, cucumber, Brassicaceae, and onion (Allium cepa) [86]. Although the previously-mentioned studies were invaluable in identifying the genomic loci or even the genes underlying metabolic changes occurring on domestication, the combination of nextgeneration sequencing and metabolomics has greatly accelerated advances in our understanding of the metabolic changes accompanying domestication.…”

“…The lower part pf the lower panel shows the metabolic changes associated with increase in size, selection for color, and introgression of resistance genes in tomato, domestication in lettuce, and the stepwise domestication of watermelon. Data from[54,77,82,84,90].…”

Transcriptome and Flavonoids Metabolomic Analysis Identifies Regulatory Networks and Hub Genes in Black and White Fruits of Lycium ruthenicum Murray

“…Anthocyanin regulation is a complex and variable process. Changes in the synthesis of a gene and transcription factor will affect the composition of the tissue (Paauw et al, 2019). Therefore, the regulation of anthocyanin metabolism of L. ruthenicum is worth further investigation and analysis.…”

“…In addition, other transcription factors also participate in anthocyanin regulation including WRKY protein, NAC protein, etc (Morishita et al, 2009;Verweij et al, 2016). The molecular mechanism of fruit color mutation has always been an important issue for researchers, because fruit color is closely related to the nutritional value, appearance, and taste of the fruit (Paauw et al, 2019). Anthocyanin pathway biosynthesis or transcription regulation encoding gene mutations are related to color phenotype.…”

Convergent seed color adaptation during repeated domestication of an ancient new world grain

“…The latter region includes a MYB-like transcription factor gene. The MYB transcription factor family is widely known for its key regulatory function in color phenotypes across the plant kingdom (Gates et al 2016) and their role in color adaptation during crop domestication has been shown for several grain crops (Paauw et al 2019). The MYB gene on chromosome 9 is an ortholog of the Anthocyanin Regulatory C1 gene in maize (Cone et al 1986), and the MYB2 gene in grape (Walker et al 2007).…”