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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.


Related in: MedlinePlus

Spatio-temporal patterns of betalain accumulation and DOD and DOD-like expression in Parakeelya mirabilis. Accumulation (A) and expression (B) in petals during flower development (C), and accumulation (D) and expression (E) in different colored petal sectors (developmental stage 5) and other organs (F). Relative expression was determined by qPCR and normalized to the geometric mean of EF1α and ACT expression. SE for three biological replicates is shown. (G) Shows petals fed a control solution (left) or a solution containing DOPA (right). The inserts show a magnification of the white petal region, with yellow pigmentation apparent in the DOPA but not control fed petals.
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Figure 2: Spatio-temporal patterns of betalain accumulation and DOD and DOD-like expression in Parakeelya mirabilis. Accumulation (A) and expression (B) in petals during flower development (C), and accumulation (D) and expression (E) in different colored petal sectors (developmental stage 5) and other organs (F). Relative expression was determined by qPCR and normalized to the geometric mean of EF1α and ACT expression. SE for three biological replicates is shown. (G) Shows petals fed a control solution (left) or a solution containing DOPA (right). The inserts show a magnification of the white petal region, with yellow pigmentation apparent in the DOPA but not control fed petals.

Mentions: Fully open flowers of Parakeelya mirabilis show four distinct color sectors of violet, white, red, and yellow (Figure 2). These were dissected and analyzed for betalain content (Figure 2 and 3), along with stamens, stigmata, ovaries, and leaves (Figure 2). It was not possible to avoid sampling a small amount of colored tissue when sampling the white sector tissue. The highest betalain content was detected in violet and red petal sectors followed by stigmata, yellow petal sectors and stamens. As was expected from the tissue dissection, a small amount of pigment was also detected in white petal sectors. Total betalain content increased markedly during petal development, with a major increase occurring between stages 2 and 3, when petals are still enclosed within the sepals. A low amount of betaxanthins was present from stage 1, while betacyanins were first detected at stage 2. Ovaries and leaves, which are green tissues, had relatively low betaxanthin content and contained no detected betacyanins.


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)

Spatio-temporal patterns of betalain accumulation and DOD and DOD-like expression in Parakeelya mirabilis. Accumulation (A) and expression (B) in petals during flower development (C), and accumulation (D) and expression (E) in different colored petal sectors (developmental stage 5) and other organs (F). Relative expression was determined by qPCR and normalized to the geometric mean of EF1α and ACT expression. SE for three biological replicates is shown. (G) Shows petals fed a control solution (left) or a solution containing DOPA (right). The inserts show a magnification of the white petal region, with yellow pigmentation apparent in the DOPA but not control fed petals.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Spatio-temporal patterns of betalain accumulation and DOD and DOD-like expression in Parakeelya mirabilis. Accumulation (A) and expression (B) in petals during flower development (C), and accumulation (D) and expression (E) in different colored petal sectors (developmental stage 5) and other organs (F). Relative expression was determined by qPCR and normalized to the geometric mean of EF1α and ACT expression. SE for three biological replicates is shown. (G) Shows petals fed a control solution (left) or a solution containing DOPA (right). The inserts show a magnification of the white petal region, with yellow pigmentation apparent in the DOPA but not control fed petals.
Mentions: Fully open flowers of Parakeelya mirabilis show four distinct color sectors of violet, white, red, and yellow (Figure 2). These were dissected and analyzed for betalain content (Figure 2 and 3), along with stamens, stigmata, ovaries, and leaves (Figure 2). It was not possible to avoid sampling a small amount of colored tissue when sampling the white sector tissue. The highest betalain content was detected in violet and red petal sectors followed by stigmata, yellow petal sectors and stamens. As was expected from the tissue dissection, a small amount of pigment was also detected in white petal sectors. Total betalain content increased markedly during petal development, with a major increase occurring between stages 2 and 3, when petals are still enclosed within the sepals. A low amount of betaxanthins was present from stage 1, while betacyanins were first detected at stage 2. Ovaries and leaves, which are green tissues, had relatively low betaxanthin content and contained no detected betacyanins.

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.


Related in: MedlinePlus