Polyploidy and Evolution in Wild and CultivatedDahliaSpecies

Gatt, Melanie K.; Ding, Hong; Hammett, K. R. W.; Murray, B. G.

doi:10.1006/anbo.1998.0614

Cited by 40 publications

(14 citation statements)

References 26 publications

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“…This correlates well with the observed low FNS II activity in the majority of black cultivars. As D. variabilis is octoploid ( 2n = 8x = 64 ) [22], it is expected that more than one FNS II copy is present as recently shown for D. variabilis CHS [9]. The decline of FNS II activity in the majority of the black cultivars, which is unusual for dahlia [3], indicates the presence of an effective regulatory mechanism, which could also include post-transcriptional or post-translational processes.…”

Section: Resultsmentioning

confidence: 98%

'Le Rouge et le Noir': A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers

et al. 2012

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BackgroundMore than 20,000 cultivars of garden dahlia (Dahlia variabilis hort.) are available showing flower colour from white, yellow and orange to every imaginable hue of red and purple tones. Thereof, only a handful of cultivars are so-called black dahlias showing distinct black-red tints. Flower colour in dahlia is a result of the accumulation of red anthocyanins, yellow anthochlors (6’-deoxychalcones and 4-deoxyaurones) and colourless flavones and flavonols, which act as copigments. White and yellow coloration occurs only if the pathway leading to anthocyanins is incomplete. Not in all cultivars the same step of the anthocyanin pathway is affected, but the lack of dihydroflavonol 4-reductase activity is frequently observed and this seems to be based on the suppression of the transcription factor DvIVS. The hitherto unknown molecular background for black colour in dahlia is here presented.ResultsBlack cultivars accumulate high amounts of anthocyanins, but show drastically reduced flavone contents. High activities were observed for all enzymes from the anthocyanin pathway whereas FNS II activity could not be detected or only to a low extent in 13 of 14 cultivars. cDNA clones and genomic clones of FNS II were isolated. Independently from the colour type, heterologous expression of the cDNA clones resulted in functionally active enzymes. FNS II possesses one intron of varying length. Quantitative Real-time PCR showed that FNS II expression in black cultivars is low compared to other cultivars. No differences between black and red cultivars were observed in the expression of transcription factors IVS and possible regulatory genes WDR1, WDR2, MYB1, MYB2, 3RMYB and DEL or the structural genes of the flavonoid pathway. Despite the suppression of FHT expression, flavanone 3-hydroxylase (FHT, synonym F3H) enzyme activity was clearly present in the yellow and white cultivars.ConclusionsAn increased accumulation of anthocyanins establishes the black flowering phenotypes. In the majority of black cultivars this is due to decreased flavone accumulation and thus a lack of competition for flavanones as the common precursors of flavone formation and the anthocyanin pathway. The low FNS II activity is reflected by decreased FNS II expression.

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Section: Resultsmentioning

confidence: 98%

'Le Rouge et le Noir': A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers

et al. 2012

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“…Because garden dahlias are autoallooctoploids (Gatt et al 1998), they may have redundant genes derived from different subfamilies. Therefore, in order to breed pure white dahlia cultivars, all CHSs belonging to different subfamilies must be suppressed.…”

Section: Discussionmentioning

confidence: 99%

“…Especially striking are the flower color variations, including purple of anthocyanins, yellow of chalcones and/or aurones, and red to orange resulting from the coexistence of both the pigments. Garden dahlias are octoploid (2n = 8x = 64) resulting from doubled allotetraploid (2n = 4x = 32) (Gatt et al 1998); this feature has enabled the production of several cultivars. Although a great variety of flower colors has been produced, almost all commercially available white-flowered cultivars are ivory white.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous post-transcriptional gene silencing of two different chalcone synthase genes resulting in pure white flowers in the octoploid dahlia

Ohno

Hosokawa

Kojima

et al. 2011

Planta

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Garden dahlias (Dahlia variabilis) are autoallooctoploids with redundant genes producing wide color variations in flowers. There are no pure white dahlia cultivars, despite its long breeding history. However, the white areas of bicolor flower petals appear to be pure white. The objective of this experiment was to elucidate the mechanism by which the pure white color is expressed in the petals of some bicolor cultivars. A pigment analysis showed that no flavonoid derivatives were detected in the white areas of petals in a star-type cultivar 'Yuino' and the two seedling cultivars 'OriW1' and 'OriW2' borne from a red-white bicolor cultivar, 'Orihime', indicating that their white areas are pure white. Semi-quantitative RT-PCR showed that in the pure white areas, transcripts of two chalcone synthases (CHS), DvCHS1 and DvCHS2 which share 69% nucleotide similarity with each other, were barely detected. Premature mRNA of DvCHS1 and DvCHS2 were detected, indicating that these two CHS genes are silenced post-transcriptionally. RNA gel blot analysis revealed that small interfering RNAs (siRNAs) derived from CHSs were produced in these pure white areas. By high-throughput sequence analysis of small RNAs in the pure white areas with no mismatch acceptance, small RNAs were mapped to two alleles of DvCHS1 and two alleles of DvCHS2 expressed in 'Yuino' petals. Therefore, we concluded that simultaneous siRNA-mediated post-transcriptional gene silencing of redundant CHS genes results in the appearance of pure white color in dahlias.

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“…Substitution of multivalents by bivalents in some individuals of S. ageratifolia boosts their fertility by eliminating all those abnormalities concomitant with polyploid meiosis. The complete restriction of homologous pairing is as a result of some form of genotypic control and bivalent may be the result of a multivalent suppressor system (Lacadena, 1996;Gatt et al, 1998). In agreement with the contentions of Levan (1940), Koul & Gohil (1970) and Kollmann (1972), the localization of chiasmata in the centromeric region thus confers an advantage on polyploids by helping them in stabilizing and behaving as diploids.…”

Section: Cytogeneticsmentioning

confidence: 93%

Cytogenetics, biogeography and biology ofSantolina ageratifoliaBarnades ex Asso (Asteraceae: Anthemideae)

Rivero-Guerra

2008

Botanical Journal of the Linnean Society

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Santolina ageratifolia Barnades ex Asso is a natural autohexaploid (2n = 6x = 54, 54 + 1B), endemic to Teruel Province, Spain and inhabits a substrate derived from sandstone, red limolite and quartzite. Three chromosome formulae are found: 30m + 12sm + 12st, present in 52% of the descendants (52 metaphase), 24m + 5m-1sm + 18sm + 6st in 39% of the descendants (39 metaphase) and 24m + 5m-1sm + 18sm + 6st + 1B in 9% of the descendants (9 metaphase). Chiasmata are mostly interstitial rather than terminal, giving rise to the formation of cruciform structures. The predominance of bivalent configurations in the meiosis and the exclusively bivalent formation in four individuals indicate that this species has a strong tendency towards diploidization. Secondary association of bivalents is observed in the number of 2, 4-6 chromosomes associated, the average being 4.21 ± 1.20 chromosomes. The variation in the chromosomal characteristics suggests chromosome translocation and/or inversions. This species is partially sterile, with a mean pollen fertility of 40.56% and a mean fructification of 34.24%. The frequencies of multivalents and pollen fertility have a strongly significant effect on fructification percentage. Phenotypic variation in habits is not correlated with karyotype characteristics. The cytogeography of the polyploid taxa of the Santolina rosmarinifolia aggregate is discussed.

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Polyploidy and Evolution in Wild and CultivatedDahliaSpecies

Cited by 40 publications

References 26 publications

'Le Rouge et le Noir': A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers

'Le Rouge et le Noir': A decline in flavone formation correlates with the rare color of black dahlia (Dahlia variabilis hort.) flowers

Simultaneous post-transcriptional gene silencing of two different chalcone synthase genes resulting in pure white flowers in the octoploid dahlia

Cytogenetics, biogeography and biology ofSantolina ageratifoliaBarnades ex Asso (Asteraceae: Anthemideae)

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