Metabolic Engineering of Flower Color Pathways Using Cytochromes P450

Abstract

A single plant species can contain more than 250 cytochromes P450. Cytochromes P450 catalyze various reactions in plant biosynthetic pathways and play critical and diversified roles in the biosynthesis of primary and specialized (secondary) compounds, including flavonoids. Flavonoids and their colored derivatives, anthocyanins, are major constituents of flower color. Functional combinations of the cytochromes P450, flavonoid 3, and flavone synthase II (FNSII, CYP93B) determine flavonoid structure and flower color. The number of hydroxyl groups on the B-ring of anthocyanins catalyzed by F3 0 H and F3 0 5 0 H have an impact on the color: the more the bluer. Wild-type or traditionally bred carnations, roses, and chrysanthemums lack blue/violet flower colors because of the deficiency of a F3 0 5 0 H and therefore lack the trihydroxylated (B-ring) anthocyanins based upon delphinidin. Metabolic engineering of the anthocyanin pathway and specifically manipulation of F3 0 5 0 H and F3 0 H genes has produced an array of flower color modifications in many species. By optimizing transgene expression and suppressing endogenous genes in a species-specific manner, transgenic carnations, roses, and chrysanthemums producing novel violet/blue-hued flowers were engineered. Downregulation of F3 0 5 0 H and F3 0 H genes, often with expression of a dihydroflavonol 4-reductase gene, yielded redder flowers in petunia, tobacco, and torenia. Modulation of FNSII gene expression also impacts flower color as flavones act as co-pigments to induce bluing of anthocyanins and flavones and anthocyanins also share the same precursors.

Completion of Tricin Biosynthesis Pathway in Rice: Cytochrome P450 75B4 Is a Unique Chrysoeriol 5′-Hydroxylase

“…Phylogenetic analysis implicated that the divergence of CYP75A and CYP75B (F39H) members predated the speciation of angiosperms (Seitz et al, 2006). However, genome sequences of several dicot plants, such as Arabidopsis, carnation, and a few Rosaceae species, do not harbor any CYP75A homologous sequences, consistent with their absence of 59-modified flavonoids (Tanaka and Brugliera, 2014). Hence, some plant lineages may have lost the CYP75A genes and the encoded F3959H enzyme activities during the course of their evolution (Tanaka and Brugliera, 2014).…”

“…However, genome sequences of several dicot plants, such as Arabidopsis, carnation, and a few Rosaceae species, do not harbor any CYP75A homologous sequences, consistent with their absence of 59-modified flavonoids (Tanaka and Brugliera, 2014). Hence, some plant lineages may have lost the CYP75A genes and the encoded F3959H enzyme activities during the course of their evolution (Tanaka and Brugliera, 2014). Interestingly, such loss was apparently compensated in some Asteraceae species (e.g.…”

Flower color modification in <i>Rosa hybrida</i> by expressing the <i>S</i>-adenosylmethionine: anthocyanin 3′,5′-<i>O</i>-methyltransferase gene from <i>Torenia hybrida</i>

“…It is rare for a single species to have a full range of flower colors, mainly because each species produces a limited range of anthocyanins due to its genetic constraints (Tanaka and Brugliera 2013;Tanaka and Brugliera 2014). Roses, carnations, and chrysanthemums account for half of the cut flower market, and they are economically important floricultural crops.…”

“…Although there has been intensive hybridization breeding to increase flower color varieties, which are based on anthocyanidins, roses (Mikanagi et al 2000;Mikanagi et al 1995) and carnations (Nakayama et al 2000) can only produce those derived from pelargonidin and cyanidin, while chrysanthemums produce cyanidin based anthocyanins (Nakayama et al 1997) but not delphinidin, while they rarely accumulate methylated anthocyanins. The expression of the flavonoid 3′,5′-hydroxylase (F3′5′H) gene (Figure 1) in these crops successfully generated delphinidin in the petals and novel flowers with blue hues were obtained, which is not possible by hybridization breeding (Tanaka and Brugliera 2013;Tanaka and Brugliera 2014). However, the production of methylated anthocyanins via genetic engineering has not been achieved in these crops.…”

The expansion and diversity of theCYP75gene family in Vitaceae

“…Both CYP75A and CYP75B genes were first identified from petunia ( Brugliera et al, 1999 ; Holton et al, 1993 ) and then from Arabidopsis thaliana ( Schoenbohm et al, 2000 ), Glycine max ( Toda et al, 2002 ), Vitis vinifera ( Castellarin et al, 2006 ), Solanum lycopersicum ( Olsen et al, 2010 ), Epimedium sagittatum ( Huang, Sun & Wang, 2012 ), Camellia sinensis ( Wang et al, 2014 ), Pohlia nutans ( Liu, Ju & Xia, 2014 ), Delphinium zalil ( Miyahara et al, 2016 ), and Hordeum vulgare ( Vikhorev, Strygina & Khlestkina, 2019 ). In many plants including Arabidopsis thaliana , Dianthus caryophyllus , and rose, there is an absence of delphinidin-based anthocyanins, indicating these plants lost CYP75A genes during the evolution ( Tanaka & Brugliera, 2013 ; Tanaka & Brugliera, 2014 ). In the Asteraceae, some F3 ′5′ H genes belong to the CYP75B genes rather than CYP75A genes, indicating the independent evolution of an Asteraceae-specific F3 ′5′ H ( Seitz et al, 2006 ).…”