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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.


Schematic of Beta vulgaris LigB genomic regions. (A) Region of Chr4 containing two related LigB genes, termed LigB Class I and DODA-like [BvDODA HQ656022]. (B) Region of Chr2 containing DODA1 [HQ656027]. The predicted transcript regions are marked with green boxes and the exons with blue boxes. Additional gene labeling is as per the Augustus annotation of the genome at the Beta vulgaris Resource (Dohm et al., 2014).
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Figure 10: Schematic of Beta vulgaris LigB genomic regions. (A) Region of Chr4 containing two related LigB genes, termed LigB Class I and DODA-like [BvDODA HQ656022]. (B) Region of Chr2 containing DODA1 [HQ656027]. The predicted transcript regions are marked with green boxes and the exons with blue boxes. Additional gene labeling is as per the Augustus annotation of the genome at the Beta vulgaris Resource (Dohm et al., 2014).

Mentions: Diversification of gene function in plant secondary metabolism during evolution often involves localized gene duplication followed by neofunctionalisation, resulting in the tandem occurrence of related biosynthetic genes (Ober, 2005). The only betalain-producing species for which a genome sequence is publically available is B. vulgaris (Dohm et al., 2014), so the structure and localisation in the genome of the three LigB sequences examined here was determined (Figure 10). All three genes have three exons, and the exon size and position of introns is conserved, with exon 1 being between 246 to 260 bp, exon 2 371 to 378 bp and exon 3 190 to 193 bp (Figure 10). BvDODA1 is located on Chr2 while both the ClassI LigB and DODA are located on Chr4. The two genes on Chr4 are on the same genomic sequence scaffold, with the end of exon 3 of DODA being ∼7.6 Kb upstream of exon 1 of the ClassI LigB gene (Figure 10).


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)

Schematic of Beta vulgaris LigB genomic regions. (A) Region of Chr4 containing two related LigB genes, termed LigB Class I and DODA-like [BvDODA HQ656022]. (B) Region of Chr2 containing DODA1 [HQ656027]. The predicted transcript regions are marked with green boxes and the exons with blue boxes. Additional gene labeling is as per the Augustus annotation of the genome at the Beta vulgaris Resource (Dohm et al., 2014).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 10: Schematic of Beta vulgaris LigB genomic regions. (A) Region of Chr4 containing two related LigB genes, termed LigB Class I and DODA-like [BvDODA HQ656022]. (B) Region of Chr2 containing DODA1 [HQ656027]. The predicted transcript regions are marked with green boxes and the exons with blue boxes. Additional gene labeling is as per the Augustus annotation of the genome at the Beta vulgaris Resource (Dohm et al., 2014).
Mentions: Diversification of gene function in plant secondary metabolism during evolution often involves localized gene duplication followed by neofunctionalisation, resulting in the tandem occurrence of related biosynthetic genes (Ober, 2005). The only betalain-producing species for which a genome sequence is publically available is B. vulgaris (Dohm et al., 2014), so the structure and localisation in the genome of the three LigB sequences examined here was determined (Figure 10). All three genes have three exons, and the exon size and position of introns is conserved, with exon 1 being between 246 to 260 bp, exon 2 371 to 378 bp and exon 3 190 to 193 bp (Figure 10). BvDODA1 is located on Chr2 while both the ClassI LigB and DODA are located on Chr4. The two genes on Chr4 are on the same genomic sequence scaffold, with the end of exon 3 of DODA being ∼7.6 Kb upstream of exon 1 of the ClassI LigB gene (Figure 10).

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.