PsbHLH1, a novel transcription factor involved in regulating anthocyanin biosynthesis in tree peony (Paeonia suffruticosa).
Qi Yu,Zhou Lin,Han Lulu,Zou Hongzhu,Miao Kun,Wang Yan
Plant physiology and biochemistry : PPB
Flower color is one of the most important features of ornamental plants. Anthocyanin composition and concentration are usually closely related to flower color formation. The biosynthesis of anthocyanin is regulated by a series of structural genes and regulatory genes. The basic helix-loop-helix proteins (bHLHs) are considered as one of the key transcription factors known as the regulators of anthocyanin biosynthesis. However, the bHLH transcription factor family of tree peony (Paeonia suffruticosa) has not been systematically studied in previous studies, especially for the regulation of petal pigmentation. The aim of this study was to identify bHLH genes and unravel their underlying molecular mechanism involved in the regulation of anthocyanin biosynthesis in tree peony. Based on transcriptome profiling analysis, we identified three bHLHs candidate anthocyanin regulators, PsbHLH1, PsbHLH2, and PsbHLH3. PsbHLH1-3 were phylogenetically clustered in the IIIf bHLH subgroup, which is involved in anthocyanin biosynthesis in other plant species. In addition, three bHLH proteins were localized in the nucleus and displayed transcriptional activation activity in a yeast hybrid system. Through a series of functional experiments, we further demonstrated that PsbHLH1 could transcriptionally activate the expression of PsDFR and PsANS via directly binding to their promoters. These results laid a solid foundation to better understand the regulatory mechanisms of anthocyanin biosynthesis in P. suffruticosa and to benefit molecular breeding of tree peony cultivars with novel color.
Differential anthocyanin accumulation in radish taproot: importance of RsMYB1 gene structure.
Lai Biao,Cheng Yuanyi,Liu Hong,Wang Qiuxia,Wang Qi,Wang Chunlan,Su Rui,Chen Fabo,Wang Huicong,Du Lina
Plant cell reports
KEY MESSAGE:RsMYB1a was the crucial MYB, and RsbHLH4 is the essential partner in regulating the anthocyanin biosynthesis in radish. There are four color types of radish according to whether or not the anthocyanin accumulates in the skin and flesh of taproot. Red radishes accumulate a substantial amount of anthocyanins in both the skin and flesh. It is well known that the MYB-bHLH-WD40 transcription factor(s) complex regulates the biosynthesis of anthocyanin in plants. Here in, four candidate MYB and bHLH genes, RsMYB1a, RsMYB1b, RsbHLH2 and RsbHLH4, were isolated from red radish 'Hongxin 1'. The expression of RsbHLH4 and the two structural genes RsANS and RsUFGT was significantly positively correlated with anthocyanin contents. The expression of RsMYB1a was also highly correlated with anthocyanin accumulation, particularly when the white flesh sample of 'Hongxin 1-1' was excluded. The transient expression of RsMYB1a in the radish cotyledon and leaf induced anthocyanin accumulation with even stronger promoting role when expression in combination with RsbHLH4. These results suggested that RsMYB1a was the crucial MYB, and that RsbHLH4 is an essential partner in regulating the biosynthesis of anthocyanins in radish. The low or undetectable RsbHLH4 expression paralleled the lack of anthocyanin accumulation in the white flesh of 'Hongxin 1-1' and 'Shaguan 1'. Assays demonstrated that RsMYB1a interacted with RsbHLH4 and activated the expression of RsbHLH4. Notably, all the dark red radish cultivars have a longer RsMYB1a genomic DNA sequence, while the short and nonfunctional RsMYB1a is present in non-red cultivars. The length of the first intron and the presence of an early stop codon of RsMYB1 might underlie the differential anthocyanin accumulation in the radish taproot.