Multiple R2R3-MYB Transcription Factors Involved in the Regulation of Anthocyanin Accumulation in Peach Flower

Abstract

Anthocyanin accumulation is responsible for flower coloration in peach. Here, we report the identification and functional characterization of eight flavonoid-related R2R3-MYB transcription factors, designated PpMYB10.2, PpMYB9, PpMYBPA1, Peace, PpMYB17, PpMYB18, PpMYB19, and PpMYB20, respectively, in peach flower transcriptome. PpMYB10.2 and PpMYB9 are able to activate transcription of anthocyanin biosynthetic genes, whilst PpMYBPA1 and Peace have a strong activation on the promoters of proanthocyanin (PA) biosynthetic genes. PpMYB17-20 show a strong repressive effect on transcription of flavonoid pathway genes such as dihydroflavonol 4-reductase. These results indicate that anthocyanin accumulation in peach flower is coordinately regulated by a set of R2R3-MYB genes. In addition, PpMYB9 and PpMYB10.2 are closely related but separated into two groups, designated MYB9 and MYB10, respectively. PpMYB9 shows a strong activation on the PpUGT78A2 promoter, but with no effect on the promoter of PpUGT78B (commonly called PpUFGT in previous studies). In contrast, PpMYB10.2 is able to activate the PpUFGT promoter, but not for the PpUGT78A2 promoter. Unlike the MYB10 gene that is universally present in plants, the MYB9 gene is lost in most dicot species. Therefore, the PpMYB9 gene represents a novel group of anthocyanin-related MYB activators, which may have diverged in function from the MYB10 genes. Our study will aid in understanding the complex mechanism regulating floral pigmentation in peach and functional divergence of the R2R3-MYB gene family in plants.

Activator‐type R2R3‐MYB genes induce a repressor‐type R2R3‐MYB gene to balance anthocyanin and proanthocyanidin accumulation

“…In order to identify the effect of PpMYB18 on PA pathway gene transcription, the promoter region of a peach PA biosynthetic gene, PpLAR1 (Zhou et al ., ) , was cloned and inserted into dual luciferase assay system. Infiltration of PpMYBPA1 alone could not activate the PpLAR1 promoter due to the fact that PpMYBPA1 was not interacting efficiently with the Nicotiana bHLH partner (Zhou et al ., ). By contrast, co‐infiltration of PpMYBPA1 with PpbHLH3 was able to activate the PpLAR1 promoter.…”

“…Recently, multiple flavonoidrelated MYB activators have been identified in peach. For example, PpMYB10.1, PpMYB10.4 and PpMYB9/PpMYB10.2 (previously named PpMYB10 in Ravaglia et al, 2013) act as positive regulators of anthocyanin accumulation in fruit, leaf and flower, respectively (Rahim et al, 2014;Tuan et al, 2015;Zhou et al, 2014Zhou et al, , 2015aZhou et al, , 2016, whereas PpMYBPA1 and PpMYB7 activate PA pathway genes in fruit (Ravaglia et al, 2013;Zhou et al, 2015b). All of these MYB activators require PpbHLH3 and/or PpbHLH33 as partners to regulate the accumulation of anthocyanins and PAs (Ravaglia et al, 2013;Zhou et al, 2015a).…”

Transcriptional Factors Regulate Plant Stress Responses Through Mediating Secondary Metabolism

“…The MYB TF family is divided into four subgroups, 1R, 2R, 3R, and 4R, depending on the repeats of DNA binding domains. Each domain contains 50-53 amino acids that form α-helices, whereas a helix-turn-helix is located between the second and third helices that facilitates MYB TFs binding to target DNA sequences [119] (Figure 1).…”

New insight into the molecular mechanism of colour differentiation among floral segments in orchids

“…The anthocyanin biosynthesis pathway (ABP) is highly conserved and has been well studied in plants 6 . As crucial ABP regulators, the R2R3-MYB transcription factors can regulate the expression of structural genes to influence flower colour formation [8][9][10][11][12][13] . In Orchidaceae, some R2R3-MYBs have been verified to activate ABP structural genes to promote anthocyanin accumulation in Phalaenopsis 5 , Oncidium 14 and Dendrobium 15 flowers.…”