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

BMC Plant Biology

Research Article

Jana Thill¹  Gerlinde Muster¹  Silvija Miosic¹  Karl Stich¹  Romel Ahmed¹  Karin Schlangen¹  Heidi Halbwirth¹ 

[1] Umwelttechnik und Technische Biowissenschaften, Technische Universität Wien, Institut für Verfahrenstechnik, Getreidemarkt 9/1665, A-1060, Wien, Austria;

关键词: Dahlia variabilis;    Asteraceae;    Flower colour;    Black flower;    Flavonoids;    Anthocyanins;    Flavones;    Flavone synthase II;    Transcription factors;   

DOI  :  10.1186/1471-2229-12-225

 received in 2012-03-20, accepted in 2012-10-19,  发布年份 2012

来源: Springer

【 摘 要 】

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.

【 授权许可】

Unknown   
© Thill et al.; licensee BioMed Central Ltd. 2012. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.