It is revealed that ethylene inhibits anthocyanin biosynthesis through a CmERF3−CmMYB4−LBGs (late biosynthetic genes) regulatory module.
Abstract
Abstract Anthocyanins are the primary determinants of floral pigmentation in Chrysanthemum ×morifolium, and ethylene acts as a key regulator of their biosynthesis. Although the ethylene-mediated regulatory circuitry is functionally important, its underlying mechanism in chrysanthemum has remained unclear. In this study, we identified CmMYB4 as a transcriptional repressor that directly suppresses the expression of key anthocyanin biosynthetic genes, including CmDFR (dihydroflavonol 4-reductase), CmUFGT (flavonoid 3-O-glucosyltransferase), and Cm3MaT (anthocyanin 3-O-glucoside-6″-O-malonyltransferase). Time-ordered gene co-expression network analysis comparing the transcriptomes of CmMYB4-overexpressing and control plants, together with molecular biology experimental results, further revealed CmERF3 (ethylene response factor 3) as a hierarchical upstream regulator of anthocyanin biosynthesis. Exogenous ethylene treatment induced CmERF3 expression while reducing anthocyanin accumulation. Subsequent functional characterization showed that the overexpression of CmERF3 suppresses anthocyanin biosynthesis in both tobacco and chrysanthemum by directly activating CmMYB4 and repressing CmDFR, CmUFGT, and Cm3MaT. Collectively, these findings revealed that ethylene inhibits anthocyanin biosynthesis through a CmERF3−CmMYB4−LBGs (late biosynthetic genes) regulatory module. This study not only elucidates the molecular mechanism governing ethylene-mediated anthocyanin inhibition but also provides new perspectives for the molecular engineering of ornamental traits in chrysanthemum.
High temperature (HT) is a crucial environmental factor influencing floral pigmentation and ornamental quality in chrysanthemum (Chrysanthemum morifolium) by modulating anthocyanin biosynthesis. In this study, comparative transcriptome profiling was performed in two F1 chrysanthemum lines (RO72 and RO99) under high-temperature stress to elucidate the molecular mechanisms behind heat-induced floral color fading. Analysis revealed extensive transcriptional reprogramming of genes associated with anthocyanin metabolism, hormonal signaling, and oxidative stress responses. While structural genes in the anthocyanin biosynthetic pathway (CHS, DFR, ANS, 3MAT and LDOX) were significantly downregulated, key glycosylation-related genes such as UFGT were upregulated, suggesting a compensatory mechanism that enhances pigment stabilization rather than de novo synthesis. This study identified a shift in the MYB–bHLH–WD40 regulatory complex, specifically the upregulation of transcriptional repressors (MYB62, MYB15) and downregulation of activators (MYB106, bHLH49), suggesting a suppressed anthocyanin accumulation. Simultaneously, genes associated with several signaling cascades such as ROS, ABA, and auxin–jasmonate signaling pathways were differentially expressed, suggesting that these alterations may contribute to the repression of pigment biosynthesis and color fading. Collectively, these results hypothesize that high temperature suppresses anthocyanin accumulation through a dual mechanism of transcriptional inhibition and hormonal modulation, while simultaneously promoting pigment stabilization via glycosylation. This study therefore provides fundamental insights into thermal regulation of floral pigmentation and identifies candidate genes and pathways potentially involved in heat-induced floral color fading in chrysanthemum.
Manjulatha Mekapogu, So-Hyeon Lim, O. Kwon et al.· Horticulturae· 1 citation
A preliminary elucidation of the molecular mechanism by which upstream transcriptional regulation of the AmFLS gene controls flavonol biosynthesis in JHK is provided, offering a theoretical basis for further elucidating the regulatory network of flavonol metabolism in JHK and accelerating its industrial development.
Da-Yun Wang, Hongtao Chu, Zhong Liu et al.· Plants· 0 citations
A MeJA-responsive DoMYB41-DoMYC2 cascade that iteratively activates DoTIP1–1 expression and promotes the biosynthesis of GMs, thereby enhancing salinity tolerance in D. officinale is uncovered and provides genetic targets for salinity tolerance in breeding programs for this horticultural orchid.
Chrysanthemum indicum var. aromaticum is a rare aromatic variant, and deciphering its molecular basis could facilitate the breeding of scented chrysanthemums. Here, we introduced its transcription factor CiMYC2 into Chrysanthemum indicum (C. indicum) to investigate the role and mechanism of CiMYC2 in regulating terpenoid biosynthesis. Results demonstrated that overexpression of CiMYC2 significantly increased the density of glandular trichomes on leaves (up to 3.94-fold) and elevated the total relative terpenoid content in leaf exudates by up to 21.88%. Transcriptomic analysis revealed strong upregulation of key terpenoid pathway genes, including CiHMGR and CiTPS4, and their induction was confirmed by quantitative real-time PCR, with CiTPS4 expression increasing up to 22.58-fold. Yeast one-hybrid (Y1H) and dual-luciferase (dual-LUC) assays confirmed that CiMYC2 directly bound to enhancer box (E-box) elements in the promoters of CiHMGR and CiTPS4 to activate their transcription. Furthermore, yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BIFC) assays showed that CiMYC2 physically interacted with specific jasmonic acid (JA) signaling repressors CiJAZ4/5/7/8. Our findings reveal that the transcription factor CiMYC2 integrates JA signaling by interacting with CiJAZ proteins and directly activates terpenoid biosynthetic genes (CiHMGR and CiTPS4), thereby promoting glandular trichome development and terpenoid accumulation in C. indicum. This work provides a theoretical basis for the molecular breeding of fragrant chrysanthemum varieties.
An integrated multi-omics analysis of dwarf and normal-height red tangerine × trifoliate orange hybrid seedlings revealed a PtARF6/8-PtGH3.1 transcriptional module that regulates auxin homeostasis through IAA conjugation, providing genetic insights into GH3.1-mediated dwarfism.
Lonicera japonica Thunb. is a traditional medicinal plant rich in bioactive flavonoids, but the transcriptional regulation of flavonoid biosynthesis remains unclear. In this study, we identified LjMYB106, an R2R3-MYB transcription factor associated with flavonoid accumulation, from floral developmental transcriptomes. Sequence and phylogenetic analyses showed that LjMYB106 contains conserved R2 and R3 MYB domains and is closely related to homologous MYB proteins. Heterologous overexpression of LjMYB106 in Arabidopsis thaliana and Nicotiana benthamiana increased total flavonoid and p-coumaric acid contents. Integrated transcriptomic and widely targeted metabolomic analyses in A. thaliana showed that LjMYB106 overexpression was associated with changes in phenylpropanoid and flavonoid biosynthetic pathways. qRT-PCR validation further showed that PAL, C4H, 4CL, CHS, DFR, and ANS homologs were up-regulated, whereas CHI, F3H, and FLS homologs were down-regulated in LjMYB106-overexpressing plants. Subcellular localization and yeast transactivation assays indicated that LjMYB106 is a nuclear protein with transcriptional activation activity. These results suggest that LjMYB106 is a candidate regulator of phenylpropanoid and flavonoid metabolism and provide a basis for further studies of MYB-mediated flavonoid regulation in L. japonica.
Jiang-Xin Yang, Jingjie Zhang, Xing-Yu Nie et al.· Frontiers in Plant Science· 0 citations
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