Dataset Information

The R2R3-MYB transcription factor GhMYB1a regulates flavonol and anthocyanin accumulation in Gerbera hybrida.

ABSTRACT: Anthocyanins and flavonols have vital roles in flower coloration, plant development, and defense. Because anthocyanins and flavonols share the same subcellular localization and common biosynthetic substrates, these pathways may compete for substrates. However, the mechanism regulating this potential competition remains unclear. Here, we identified GhMYB1a, an R2R3-MYB transcription factor involved in the regulation of anthocyanin and flavonol accumulation in gerbera (Gerberahybrida). GhMYB1a shares high sequence similarity with that of other characterized regulators of flavonol biosynthesis. In addition, GhMYB1a is also phylogenetically grouped with these proteins. The overexpression of GhMYB1a in gerbera and tobacco (Nicotianatabacum) resulted in decreased anthocyanin accumulation and increased accumulation of flavonols by upregulating the structural genes involved in flavonol biosynthesis. We further found that GhMYB1a functions as a homodimer instead of interacting with basic helix-loop-helix cofactors. These results suggest that GhMYB1a is involved in regulating the anthocyanin and flavonol metabolic pathways through precise regulation of gene expression. The functional characterization of GhMYB1a provides insight into the biosynthesis and regulation of flavonols and anthocyanins.

SUBMITTER: Zhong C

PROVIDER: S-EPMC7237480 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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The R2R3-MYB transcription factor GhMYB1a regulates flavonol and anthocyanin accumulation in Gerbera hybrida.

Zhong Chunmei C Tang Yi Y Pang Bin B Li Xukun X Yang Yuping Y Deng Jing J Feng Chengyong C Li Lingfei L Ren Guiping G Wang Yaqin Y Peng Jianzong J Sun Shulan S Liang Shan S Wang Xiaojing X

Horticulture research 20200520

Anthocyanins and flavonols have vital roles in flower coloration, plant development, and defense. Because anthocyanins and flavonols share the same subcellular localization and common biosynthetic substrates, these pathways may compete for substrates. However, the mechanism regulating this potential competition remains unclear. Here, we identified GhMYB1a, an R2R3-MYB transcription factor involved in the regulation of anthocyanin and flavonol accumulation in gerbera (Gerberahybr ...[more]

PMID: 32435501

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Project description:Flavonols as plant secondary metabolites with vital roles in plant development and defense against UV light, have been demonstrated to be the main bioactive components (BCs) in the genus Epimedium plants, several species of which are used as materials for Herba Epimedii, an important traditional Chinese medicine. The flavonol biosynthetic pathway genes had been already isolated from Epimedium sagittatum, but a R2R3-MYB transcription factor regulating the flavonol synthesis has not been functionally characterized so far in Epimedium plants. In this study, we isolated and characterized the R2R3-MYB transcription factor EsMYBF1 involved in regulation of the flavonol biosynthetic pathway from E. sagittatum. Sequence analysis indicated that EsMYBF1 belongs to the subgroup 7 of R2R3-MYB family which contains the flavonol-specific MYB regulators identified to date. Transient reporter assay showed that EsMYBF1 strongly activated the promoters of EsF3H (flavanone 3-hydroxylase) and EsFLS (flavonol synthase), but not the promoters of EsDFRs (dihydroflavonol 4-reductase) and EsANS (anthocyanidin synthase) in transiently transformed Nicotiana benthamiana leaves. Both yeast two-hybrid assay and transient reporter assay validated EsMYBF1 to be independent of EsTT8, or AtTT8 bHLH regulators of the flavonoid pathway as cofactors. Ectopic expression of EsMYBF1 in transgenic tobacco resulted in the increased flavonol content and the decreased anthocyanin content in flowers. Correspondingly, the structural genes involved in flavonol synthesis were upregulated in the EsMYBF1 overexpression lines, including NtCHS (chalcone synthase), NtCHI (chalcone isomerase), NtF3H and NtFLS, whereas the late biosynthetic genes of the anthocyanin pathway (NtDFR and NtANS) were remarkably downregulated, compared to the controls. These results suggest that EsMYBF1 is a flavonol-specific R2R3-MYB regulator, and involved in regulation of the biosynthesis of the flavonol-derived BCs in E. sagittatum. Thus, identification and functional characterization of EsMYBF1 provide insight into understanding the biosynthesis and regulation of the flavonol-derived BCs in Epimedium plants, and also provide an effective tool gene for genetic manipulation to improve the flavonol synthesis.

Project description:Anthocyanins spatiotemporally accumulate in certain tissues of particular species in the banana plant, and MYB transcription factors (TFs) serve as their primary regulators. However, the precise regulatory mechanism in banana remains to be determined. Here, we report the identification and characterization of MaMYB4, an R2R3-MYB repressor TF, characterized by the presence of EAR (ethylene-responsive element binding factor-associated amphiphilic repression) and TLLLFR motifs. MaMYB4 expression was induced by the accumulation of anthocyanins. Transgenic banana plants overexpressing MaMYB4 displayed a significant reduction in anthocyanin compared to wild type. Consistent with the above results, metabolome results showed that there was a decrease in all three identified cyanidins and one delphinidin, the main anthocyanins that determine the color of banana leaves, whereas both transcriptome and reverse transcription-quantitative polymerase chain reaction analysis showed that many key anthocyanin synthesis structural genes and TF regulators were downregulated in MaMYB4 overexpressors. Furthermore, dual-luciferase assays showed that MaMYB4 was able to bind to the CHS, ANS, DFR, and bHLH promoters, leading to inhibition of their expression. Yeast two-hybrid analysis verified that MaMYB4 did not interact with bHLH, which ruled out the possibility that MaMYB4 could be incorporated into the MYB-bHLH-WD40 complex. Our results indicated that MaMYB4 acts as a repressor of anthocyanin biosynthesis in banana, likely due to a two-level repression mechanism that consists of reduced expression of anthocyanin synthesis structural genes and the parallel downregulation of bHLH to interfere with the proper assembly of the MYB-bHLH-WD40 activation complex. To the best of our knowledge, this is the first MYB TF that regulates anthocyanin synthesis that was identified by genetic methods in bananas, which will be helpful for manipulating anthocyanin coloration in banana programs in the future.

Dataset Information

The R2R3-MYB transcription factor GhMYB1a regulates flavonol and anthocyanin accumulation in Gerbera hybrida.

Publications

The R2R3-MYB transcription factor GhMYB1a regulates flavonol and anthocyanin accumulation in <i>Gerbera hybrida</i>.

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