AUTHOR=Luo Ping , Ning Guogui , Wang Zhen , Shen Yuxiao , Jin Huanan , Li Penghui , Huang Shasha , Zhao Jian , Bao Manzhu 

TITLE=Disequilibrium of Flavonol Synthase and Dihydroflavonol-4-Reductase Expression Associated Tightly to White vs. Red Color Flower Formation in Plants

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.01257

DOI=10.3389/fpls.2015.01257

ISSN=1664-462X

ABSTRACT=<p>Flower color is the main character throughout the plant kingdom. Though substantial information exists regarding the structural and regulatory genes involved in anthocyanin and flavonol biosynthesis, little is known that what make a diverse white vs. red color flower in natural species. Here, the contents of pigments in seven species from varied phylogenetic location in plants with red and white flowers were determined. Flavonols could be detected in red and white flowers, but anthocyanins were almost undetectable in the white cultivar. Comparisons of expression patterns of gene related to the flavonoid biosynthesis indicated that disequilibrium expression of flavonol synthase (<italic>FLS</italic>) and dihydroflavonol-4-reductase (<italic>DFR</italic>) genes determined the accumulation of flavonols and anothcyanins in both red and white flowers of seven species. To further investigate the role of such common regulatory patterns in determining flower color, <italic>FLS</italic> genes were isolated from <italic>Rosa rugosa</italic> (<italic>RrFLS1</italic>), <italic>Prunus persica</italic> (<italic>PpFLS</italic>), and <italic>Petunia hybrida</italic> (<italic>PhFLS</italic>), and <italic>DFR</italic> genes were isolated from <italic>Rosa rugosa</italic> (<italic>RrDFR1</italic>) and <italic>Petunia hybrida</italic> (<italic>PhDFR</italic>). Heterologous expression of the <italic>FLS</italic> genes within tobacco host plants demonstrated conservation of function, with the transgenes promoting flavonol biosynthesis and inhibiting anthocyanin accumulation, so resulting in white flowers. Conversely, overexpression of <italic>DFR</italic> genes in tobacco displayed down-regulation of the endogenous <italic>NtFLS</italic> gene, and the promotion of anthocyanin synthesis. On this basis, we propose a model in which FLS and DFR gene-products compete for common substrates in order to direct the biosynthesis of flavonols and anthocyanins, respectively, thereby determining white vs. red coloration of flowers.</p>