“La Vie en Rose”: Biosynthesis, Sources, and Applications of Betalain Pigments  Guy Polturak, Asaph Aharoni  Molecular Plant  Volume 11, Issue 1, Pages 7-22 (January 2018) DOI: 10.1016/j.molp.2017.10.008 Copyright © 2017 The Author Terms and Conditions

Figure 1 Representative Betalain Structures, Exemplifying Betalain Glucosylation, Acylation, Decarboxylation, and Isomerization. Compounds are categorized into one betaxanthin and four betacyanin groups: betanin (betanidin 5-O-β-glucoside), gomphrenin (betanidin 6-O-β-glucoside), amaranthin (5-O-β-glucuronosylglucoside), and bougainvillein (betanidin 5-O-β-sophoroside or betanidin 6-O-β-sophoroside). Betalains are frequently named after the species from which they were first isolated. Molecular Plant 2018 11, 7-22DOI: (10.1016/j.molp.2017.10.008) Copyright © 2017 The Author Terms and Conditions

Figure 2 The Betalain Biosynthetic Pathway. Several betacyanins are given as examples for betanin acylation or glycosylation reactions. Dashed lines designate reactions of an alternative pathway, in which cyclo-DOPA is first glucosylated and then condensates with betalamic acid to form betanin. Additional decoration reactions (e.g., glucuronidation) may occur on cyclo-DOPA-glucoside instead of betanin (not shown in the scheme). Betanidin can also be glucosylated at the 6′O position to form gomphrenin (not shown in scheme). Spon., spontaneous condensation reactions. Molecular Plant 2018 11, 7-22DOI: (10.1016/j.molp.2017.10.008) Copyright © 2017 The Author Terms and Conditions

Figure 3 Metabolic Engineering of Betalains in Plants and Microbes. (A) Flowers of wild-type (bottom right) and three betalain-producing tobacco lines. (B) Cell-suspension cultures of wild-type (left) and betalain-producing BY2 tobacco cell lines. (C) Ripe and unripe fruit of a betalain-producing tomato line. (D) Betalains accumulate in both roots and shoots of transgenic tobacco plants. Molecular Plant 2018 11, 7-22DOI: (10.1016/j.molp.2017.10.008) Copyright © 2017 The Author Terms and Conditions

Figure 4 L-DOPA-Derived Metabolites. L-DOPA is a precursor in biosynthetic pathways leading to formation of betalains (e.g., betanin), benzylisoquinoline alkaloids (e.g., morphine, codeine, berberine), ipecac alkaloids (e.g., emetine), and phenetylisoquinoline alkaloids (e.g., colchicine). Dashed lines designate multiple reactions. Molecular Plant 2018 11, 7-22DOI: (10.1016/j.molp.2017.10.008) Copyright © 2017 The Author Terms and Conditions