3
Modifying Anthocyanin Production in Flowers
Kevin M. Davies
New Zealand Institute for Crop & Food Rearch Ltd, Private Bag 11600, Palmerston North, New Zealand, i.nz
Abstract. Anthocyanin biosynthesis is a key aspect of flower development for many angio-sperms, providing one of the major influences on the choice of potential pollinators. In some species evolution has resulted in complex anthocyanin structures that provide bright flower colours, whereas in other species sophisticated combinations of pigment patterning and floral shape have developed to attract pollinators. There is now a good understanding of the molecu-lar biology of both the genes encoding the biosynthetic enzymes for anthocyanins and copig-ments, and the temporal and spatial regulation of anthocyanin production. The availability of genes relating to anthocyanin biosynthesis has allowed for the molecular breeding of flower colour in veral ornamental species. Since the first publication detailing the generation of new flower colours using recombinant DNA techniques (approximately 20 years ago) there have been many notable advances in the gene technologies available for genetic mod
ification of anthocyanin biosynthesis. Transgenic carnation cultivars that produce delphinidin-derived anthocyanins and that have novel mauve-violet colours are now available commercially, and it is anticipated that the will be followed to market by many more genetically modified orna-mental crops during the next 10 to 15 years.
3.1 Introduction
The major pigments that cau flower colour are carotenoids, flavonoids and betalains. Although other pigment types such as chlorophylls, phenylphenalenones and quino-chalcones can generate flower colours, they are rare examples (Davies 2004). The flavonoids are phenylpropanoid compounds of great variation in structure and function (Bohm 1998). Tho involved in flower colour are water-soluble and generally located in the vacuole, with by far the most common type being the anthocyanins. Antho-cyanins are the basis for nearly all pink, red, orange, scarlet, purple, blue and blue-black flower colours. Although flavonoids such as the yellow aurones also give ri to flower colours, they are comparatively rare, and only the anthocyanin pigments are discusd in detail in this review. Recent reviews of the biosynthesis of other pigment types include tho of Strack et al. (2003) and Zrÿd and Christinet (2004) on betalains, Cuttriss and Pogson (2004) and Frar and Bramley (2004) on carotenoids, and that of Davies (2004) on some of the less common pigment type
s.
K. Gould et al. (eds.), Anthocyanins,DOI: 10.1007/978-0-387-77335-3_3,
© Springer Science+Business Media, LLC 2009
50 K.M.
Davies
Flavonoid biosynthesis is part of the larger phenylpropanoid pathway, which produces a range of condary metabolites from the aromatic amino acid phenyla-lanine. There are many branches to the flavonoid-specific pathway, producing col-oured and colourless compounds with diver biological functions. As mentioned above, anthocyanins are the most significant flavonoid pigments, with aurones, chal-cones and some flavonols playing a limited role in flower colour. The generally colourless (or weakly coloured) flavones and flavonols also have a role in flower colour for their function as co-pigments. They stabili and maintain anthocyanins in their coloured forms, in a process of complex molecular interactions known as co-pigmentation (Brouillard and Dangles 1993). Flavones and flavonols, strong absorb-ers of UV-light, are also the basis for some floral inct nectar guides.
This review focus on the current status of gene technologies for manipulating anthocyanin production in flowers. To help with understanding of the various genetic modification (GM) approaches discusd, a brief overview is also given of the bio-synthetic pathway for anthocyanins, the regulation of anthocyanin production, and the character of anthocyanins as flower pigments.
3.2 Anthocyanin Biosynthesis in Flowers
The anthocyanin biosynthetic pathway is well defined at the genetic and enzymatic level, with gene quences available for all the key biosynthetic steps to the primary anthocyanins and also for many of the condary modification activities. Extensive reviews have been published on the molecular biology of flavonoid biosynthesis (e.g. Springob et al. 2003; Schwinn and Davies 2004; Davies and Schwinn 2006; Grote-wold 2006), and only a brief overview is given here. There are also reviews available on some of the specific biosynthetic enzyme groups, including acyltransferas (Na-kayama et al. 2003), glycosyltransferas (Vogt 2000), methyltransferas (Ibrahim and Muzac 2000) and flavonoid dioxygenas (Gebhardt et al. 2005).
The ba pigments are the anthocyanidins, which are then glycosylated to form the anthocyanins. In all examples to date, except for one recent report of C-glycosylation (Saito et al. 2003), only O-glycotopnotch
sylation occurs for anthocyanins in plants. The core of the anthocyanidin is a 15-carbon (C15) structure of two aromatic rings (the A and B rings) joined by a third ring of C3O1 (the C-ring; Fig. 3.1). The degree of oxidation of the C-ring defines the various flavonoid types (Fig. 3.2). Anthocyanidins have two double bonds in the C-ring – and hence carry a positive charge.
The core anthocyanidin structure is modified by the addition of a wide range of chemical groups, in particular through hydroxylation, acylation and methylation. Hydroxylation and methylation usually, but not exclusively, occur on the anthocya-nidin prior to further modifications. Thus, there are a small number of anthocyanidin types that have been identified as the basis of the subquent large number of known anthocyanins with differing glycosylation and acylation patterns. Table 3.1 lists some of the 31 known naturally occurring anthocyanidin types. Not listed are some of the more recent structures identified, which include anthocyanidins with addi-tional rings incorporated, for example the pyranoanthocyanidins and riccionidin A. The structure of violet rosacyanin B (5-carboxypyranoanthocyanidin), which has
Modifying Anthocyanin Production in Flowers51
been isolated from ro (Rosa hybrida) petals and red onion bulbs (Allium cepa)
(Fukui et al. 2002; Andern and Jordheim 2006), is shown in Fig. 3.1.
Table 3.1 Structures of some of the naturally occurring anthocyanidins. The numbering of the
relevant carbons for the ba anthocyanidin structure is shown in Fig. 3.1
Substitution pattern at numbered position
6
7
3
十五从军征扩写
5
3£4£5£
Common anthocyanidins
Pelargonidin (Pg) OH OH H OH H OH H
(Cy) OH OH H OH OH OH H
Cyanidin
Delphinidin (Dp) OH OH H OH OH OH OH
OMe
OH
OH
H
H
Peonidin OH
OH
OH
OH
OMe
OH
Petunidin OH
OH
H
OH
OMe
OMe
H
Malvidin OH
OH
客服话术大全OH
3-Deoxyanthocyanidins
OH
H
H
OH
Apigeninidin H
H
OH
仙人掌的样子Luteolinidin H OH H OH OH OH H
Tricetinidin H OH H OH OH OH OH
6-Hydroxyanthocyanidins
OH
H
H
OH
6-Hydroxypelargonidin OH
OH
OH
6-Hydroxycyanidin OH OH OH OH OH OH H
6-Hydroxydelphinidin OH OH OH OH OH OH OH
Rare methylated anthocyanidins
OH
H
OH
OH
H
5-Methoxycyanidin OH
OMe
OH
OH
OH
OH
5-Methoxydelphinidin OH
OMe
H
5-Methoxypetunidin (Europinidin) OH OMe H OH OMe OH OH
5-Methoxymalvidin (Capensinidin) OH OMe H OH OMe OH OMe
OH
OMe
H
H OMe
7-Methoxypeonidin (Rosinidin) OH
OH
OMe
OMe
OH
OH H OMe
7-Methoxymalvidin (Hirsutidin) OH
£
Fig. 3.1 Anthocyanidin structures. The structure on the left (pelargonidin) shows the number-
ing of some of the carbons for the common anthocyanidins and anthocyanins. The structure of
rosacyanin B, a pyranoanthocyanidin, is shown on the right
52 K.M.
Davies
效成语
4-Coumaroyl-CoA
王者荣耀英雄海报Aureusidin
Apigenin
Kaempferol
Pelargonidin 3-O-glucoside
4CL
C4H
Acetyl-CoA离别的诗句古诗
Aurone墨西哥的英文
Flavonol
Flavone
Anthocyanin
Fig. 3.2 A ction of the general phenylpropanoid and flavonoid biosynthetic pathways lead-ing to the anthocyanins and other flavonoids found in flowers. For ea of prentation, gener-ally only the route for flavonoids with 4£-hydroxylation of the B-ring is shown. For formation of anthocyanins from leucoanthocyanidins only the simplified scheme via the anthocyanidin is shown. Enzyme abbreviations are defined in the text except for PAL (phenylalanine ammonia lya) and 4CL (4-coumaroyl CoA:liga)
Modifying Anthocyanin Production in Flowers53 Of particular relevance to this chapter are the six co
mmon anthocyanidins that have C-3,5,7 hydroxylation of the A- and C-rings, as the account for about 90% of the anthocyanins that have been identified to date (Andern and Jordheim 2006), and the 3-deoxyanthocyanidins. Anthocyanin hydroxylation patterns are of prime importance in flower colour, as they have a major effect on the colour resulting from the pigment. A comparison of the colours of the common 3-hydroxyanthocyanidins to two of the equivalent 3-deoxyanthocyanidins is shown in Fig. 3.3.
The key flavonoid precursors are phenylalanine and malonyl-CoA, derived from the shikimate/arogenate pathway and the TCA cycle, respectively. The first flavon-oids are the C15 chalcones, which are formed by chalcone syntha (CHS), a member of the polyketide syntha group of enzymes. CHS takes a hydroxycinnamic acid-CoA ester unit, usually p-coumaroyl-CoA, and carries out three quential additions of the “extender” molecule malonyl-CoA.
The chalcones are the first coloured flavonoid, and provide yellow colouration to petals of a few plant species, most notably carnation (Dianthus caryophyllus). They
Fig. 3.3 Top row: Flowers of lisianthus cultivars pigmented predominately by pelargonidin- (left), cyanidin- (centre) or delphinidin-bad (right) anthocyanins. Centre row left: Solutions of, from left to right, pelargonidin, cyanidin, delphinidin, apigeninidin (3-deoxypelargonidin) and luteolinidin (3-deoxycyanidin). Centre row right: 3-Deoxyanthocyanin pigmented flowers of Sinningia cardinalis. Bottom row left: Floral organs of the Black Bat Flower. Bottom row centre and right: The floral organs of calla lily Treasure and a clo up of the epidermis of the
spathe of the same cultivar. See Plate 2 for colour version of the photographs
