Limits...
Characterisation of betalain biosynthesis in Parakeelya flowers identifies the key biosynthetic gene DOD as belonging to an expanded LigB gene family that is conserved in betalain-producing species.

Chung HH, Schwinn KE, Ngo HM, Lewis DH, Massey B, Calcott KE, Crowhurst R, Joyce DC, Gould KS, Davies KM, Harrison DK - Front Plant Sci (2015)

Bottom Line: In addition to a LigB gene similar to that of non-Caryophyllales species (Class I genes), two other P. mirabilis LigB genes were found (DOD and DOD-like, termed Class II).The major betacyanin was the unglycosylated betanidin rather than the commonly found glycosides, an occurrence for which there are a few previous reports.A Class I LigB sequence from the anthocyanin-producing Caryophyllaceae species Dianthus superbus and two DOD-like sequences from the Amaranthaceae species Beta vulgaris and Ptilotus spp. did not show DOD activity in the transient assay.

View Article: PubMed Central - PubMed

Affiliation: Centre for Native Floriculture, School of Agriculture and Food Sciences, The University of Queensland, Gatton QLD, Australia.

ABSTRACT
Plant betalain pigments are intriguing because they are restricted to the Caryophyllales and are mutually exclusive with the more common anthocyanins. However, betalain biosynthesis is poorly understood compared to that of anthocyanins. In this study, betalain production and betalain-related genes were characterized in Parakeelya mirabilis (Montiaceae). RT-PCR and transcriptomics identified three sequences related to the key biosynthetic enzyme Dopa 4,5-dioxgenase (DOD). In addition to a LigB gene similar to that of non-Caryophyllales species (Class I genes), two other P. mirabilis LigB genes were found (DOD and DOD-like, termed Class II). PmDOD and PmDOD-like had 70% amino acid identity. Only PmDOD was implicated in betalain synthesis based on transient assays of enzyme activity and correlation of transcript abundance to spatio-temporal betalain accumulation. The role of PmDOD-like remains unknown. The striking pigment patterning of the flowers was due to distinct zones of red betacyanin and yellow betaxanthin production. The major betacyanin was the unglycosylated betanidin rather than the commonly found glycosides, an occurrence for which there are a few previous reports. The white petal zones lacked pigment but had DOD activity suggesting alternate regulation of the pathway in this tissue. DOD and DOD-like sequences were also identified in other betalain-producing species but not in examples of anthocyanin-producing Caryophyllales or non-Caryophyllales species. A Class I LigB sequence from the anthocyanin-producing Caryophyllaceae species Dianthus superbus and two DOD-like sequences from the Amaranthaceae species Beta vulgaris and Ptilotus spp. did not show DOD activity in the transient assay. The additional sequences suggests that DOD is part of a larger LigB gene family in betalain-producing Caryophyllales taxa, and the tandem genomic arrangement of two of the three B. vulgaris LigB genes suggests the involvement of duplication in the gene family evolution.

No MeSH data available.


Putative core betalain biosynthetic pathway in plants. S, spontaneous reaction; the primary enzymatic reactions are tyrosine hydroxylating activity (TyH), the enzyme for which has not been unequivocally determined; CYP76AD1, a cytochrome P450 enzyme that catalyzes oxidation of L-DOPA for the formation of cyclo-DOPA; and DOPA 4,5-dioxygenase (DOD) catalyzing the cleavage of L-DOPA needed for the formation of betalamic acid. Betacyanins normally accumulate as glycosides and may also be acylated. Regarding glucosylation at the 5-O-position, it appears that it is primarily done by cyclo-DOPA 5-O-glucosyltransferase (5GT) prior to the conjugation that forms the betacyanin.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4493658&req=5

Figure 1: Putative core betalain biosynthetic pathway in plants. S, spontaneous reaction; the primary enzymatic reactions are tyrosine hydroxylating activity (TyH), the enzyme for which has not been unequivocally determined; CYP76AD1, a cytochrome P450 enzyme that catalyzes oxidation of L-DOPA for the formation of cyclo-DOPA; and DOPA 4,5-dioxygenase (DOD) catalyzing the cleavage of L-DOPA needed for the formation of betalamic acid. Betacyanins normally accumulate as glycosides and may also be acylated. Regarding glucosylation at the 5-O-position, it appears that it is primarily done by cyclo-DOPA 5-O-glucosyltransferase (5GT) prior to the conjugation that forms the betacyanin.

Mentions: In contrast to the phenylalanine-derived anthocyanins/flavonoids, betalains are derived from tyrosine. Betalamic acid (BA) is the chromophore of all plant betalains. In betalain biosynthesis (Figure 1), tyrosine is hydroxylated to form 3,4 dihydroxyphenylalanine (DOPA). A 4,5 aromatic ring cleavage of DOPA is then required to form BA, which proceeds through an unstable 4,5-seco-DOPA intermediate that spontaneously rearranges to form BA (Fischer and Dreiding, 1972; Schliemann et al., 1998). DOPA is also oxidized to O-DOPA-quinone, which spontaneously rearranges to form cyclo-DOPA, the key moiety that determines betacyanin formation. The conjugation reactions that form the pigments are thought to occur spontaneously (Strack et al., 2003; Harris et al., 2012) and involve cyclo-DOPA (or its glycoside) and BA for betacyanin synthesis, and BA and an amino acid or amine derivative other than cyclo-DOPA for betaxanthins. Thus, only three primary enzymatic reactions are thought to be involved in the pathway from tyrosine to the first colored compounds. Betalains are stored in the vacuole and betacyanins are normally stored as glycosides, with glucosylation possible at either the betanidin or cyclo-DOPA steps of the biosynthetic pathway (Strack et al., 2003; Sakuta, 2014).


Characterisation of betalain biosynthesis in Parakeelya flowers identifies the key biosynthetic gene DOD as belonging to an expanded LigB gene family that is conserved in betalain-producing species.

Chung HH, Schwinn KE, Ngo HM, Lewis DH, Massey B, Calcott KE, Crowhurst R, Joyce DC, Gould KS, Davies KM, Harrison DK - Front Plant Sci (2015)

Putative core betalain biosynthetic pathway in plants. S, spontaneous reaction; the primary enzymatic reactions are tyrosine hydroxylating activity (TyH), the enzyme for which has not been unequivocally determined; CYP76AD1, a cytochrome P450 enzyme that catalyzes oxidation of L-DOPA for the formation of cyclo-DOPA; and DOPA 4,5-dioxygenase (DOD) catalyzing the cleavage of L-DOPA needed for the formation of betalamic acid. Betacyanins normally accumulate as glycosides and may also be acylated. Regarding glucosylation at the 5-O-position, it appears that it is primarily done by cyclo-DOPA 5-O-glucosyltransferase (5GT) prior to the conjugation that forms the betacyanin.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493658&req=5

Figure 1: Putative core betalain biosynthetic pathway in plants. S, spontaneous reaction; the primary enzymatic reactions are tyrosine hydroxylating activity (TyH), the enzyme for which has not been unequivocally determined; CYP76AD1, a cytochrome P450 enzyme that catalyzes oxidation of L-DOPA for the formation of cyclo-DOPA; and DOPA 4,5-dioxygenase (DOD) catalyzing the cleavage of L-DOPA needed for the formation of betalamic acid. Betacyanins normally accumulate as glycosides and may also be acylated. Regarding glucosylation at the 5-O-position, it appears that it is primarily done by cyclo-DOPA 5-O-glucosyltransferase (5GT) prior to the conjugation that forms the betacyanin.
Mentions: In contrast to the phenylalanine-derived anthocyanins/flavonoids, betalains are derived from tyrosine. Betalamic acid (BA) is the chromophore of all plant betalains. In betalain biosynthesis (Figure 1), tyrosine is hydroxylated to form 3,4 dihydroxyphenylalanine (DOPA). A 4,5 aromatic ring cleavage of DOPA is then required to form BA, which proceeds through an unstable 4,5-seco-DOPA intermediate that spontaneously rearranges to form BA (Fischer and Dreiding, 1972; Schliemann et al., 1998). DOPA is also oxidized to O-DOPA-quinone, which spontaneously rearranges to form cyclo-DOPA, the key moiety that determines betacyanin formation. The conjugation reactions that form the pigments are thought to occur spontaneously (Strack et al., 2003; Harris et al., 2012) and involve cyclo-DOPA (or its glycoside) and BA for betacyanin synthesis, and BA and an amino acid or amine derivative other than cyclo-DOPA for betaxanthins. Thus, only three primary enzymatic reactions are thought to be involved in the pathway from tyrosine to the first colored compounds. Betalains are stored in the vacuole and betacyanins are normally stored as glycosides, with glucosylation possible at either the betanidin or cyclo-DOPA steps of the biosynthetic pathway (Strack et al., 2003; Sakuta, 2014).

Bottom Line: In addition to a LigB gene similar to that of non-Caryophyllales species (Class I genes), two other P. mirabilis LigB genes were found (DOD and DOD-like, termed Class II).The major betacyanin was the unglycosylated betanidin rather than the commonly found glycosides, an occurrence for which there are a few previous reports.A Class I LigB sequence from the anthocyanin-producing Caryophyllaceae species Dianthus superbus and two DOD-like sequences from the Amaranthaceae species Beta vulgaris and Ptilotus spp. did not show DOD activity in the transient assay.

View Article: PubMed Central - PubMed

Affiliation: Centre for Native Floriculture, School of Agriculture and Food Sciences, The University of Queensland, Gatton QLD, Australia.

ABSTRACT
Plant betalain pigments are intriguing because they are restricted to the Caryophyllales and are mutually exclusive with the more common anthocyanins. However, betalain biosynthesis is poorly understood compared to that of anthocyanins. In this study, betalain production and betalain-related genes were characterized in Parakeelya mirabilis (Montiaceae). RT-PCR and transcriptomics identified three sequences related to the key biosynthetic enzyme Dopa 4,5-dioxgenase (DOD). In addition to a LigB gene similar to that of non-Caryophyllales species (Class I genes), two other P. mirabilis LigB genes were found (DOD and DOD-like, termed Class II). PmDOD and PmDOD-like had 70% amino acid identity. Only PmDOD was implicated in betalain synthesis based on transient assays of enzyme activity and correlation of transcript abundance to spatio-temporal betalain accumulation. The role of PmDOD-like remains unknown. The striking pigment patterning of the flowers was due to distinct zones of red betacyanin and yellow betaxanthin production. The major betacyanin was the unglycosylated betanidin rather than the commonly found glycosides, an occurrence for which there are a few previous reports. The white petal zones lacked pigment but had DOD activity suggesting alternate regulation of the pathway in this tissue. DOD and DOD-like sequences were also identified in other betalain-producing species but not in examples of anthocyanin-producing Caryophyllales or non-Caryophyllales species. A Class I LigB sequence from the anthocyanin-producing Caryophyllaceae species Dianthus superbus and two DOD-like sequences from the Amaranthaceae species Beta vulgaris and Ptilotus spp. did not show DOD activity in the transient assay. The additional sequences suggests that DOD is part of a larger LigB gene family in betalain-producing Caryophyllales taxa, and the tandem genomic arrangement of two of the three B. vulgaris LigB genes suggests the involvement of duplication in the gene family evolution.

No MeSH data available.