The genetic and molecular basis underlying anthocyanin accumulation in mei is revealed and a PmbHLH162-PmMYC2 regulatory module in which PmbHLH162 enhances PmMYC2-mediated activation of key anthocyanin biosynthetic genes is identified.
Abstract
Anthocyanin accumulation is a vital agronomic and ornamental trait, as it not only contributes to adaptation to environmental stress but also enhances ornamental value. In this study, a genome-wide association study (GWAS) was conducted using 328 accessions of mei (Prunus mume) to identify single nucleotide polymorphisms (SNPs) associated with red pigmentation in petals, filaments, and xylem. Based on these significant SNPs, we defined two haplotypes (bHLH162hap1 and bHLH162hap2) and identified PmbHLH162, a bHLH transcription factor gene responsible for anthocyanin biosynthesis regulation. Transient silencing of PmbHLH162 in mei petals via Agrobacterium-mediated transformation resulted in significant color fading, whereas its overexpression dramatically elevated anthocyanin levels. Haplotype analysis showed that two promoter variants in bHLH162hap2 (Chr03_2669885 A/C and Chr03_2670272 A/G) alter the binding affinity of transcription factors PmWRKY18 and PmWRKY70. Stronger binding to the G/C alleles gave rise to higher PmbHLH162 expression in bHLH162hap2, thereby promoted red pigmentation in multiple tissues. By contrast, accessions carrying bHLH162hap1 displayed light/colorless phenotype without accumulation of red pigment. Furthermore, PmbHLH162 interacted respectively with PmMYC2, PmTT8, and PmEGL1 to form heterodimers, and markedly enhanced PmMYC2-mediated transcriptional activation of the anthocyanin biosynthetic structural genes PmCHS and PmANS. Geographic haplotype analysis revealed that bHLH162hap2 was predominantly enriched in high-latitude northern populations but was declining markedly at lower latitudes. Collectively, our study reveals the genetic and molecular basis underlying anthocyanin accumulation in mei and identifies a PmbHLH162-PmMYC2 regulatory module in which PmbHLH162 enhances PmMYC2-mediated activation of key anthocyanin biosynthetic genes. The additional interactions of PmbHLH162 with the MBW-associated bHLH factors PmTT8 and PmEGL1 further suggest potential crosstalk between this module and the canonical anthocyanin regulatory network.
Anthocyanin biosynthesis is a key process determining flower color in lotus. In this study, 145 MYB transcription factors were identified from the lotus genome, of which 124 belong to the R2R3-MYB subfamily. Based on phylogenetic analysis and short-term light-induced transcriptome data, NnMYB38 and NnMYB114 were selected for further characterization. Expression of NnMYB38 and NnMYB114 was significantly higher in red-flowered lotus, with NnMYB38 showing a positive correlation with anthocyanin content. Transient overexpression in Nicotiana benthamiana revealed that NnMYB38 induced significant anthocyanin accumulation by upregulating multiple structural genes. In transgenic Arabidopsis, both MYB TFs promoted anthocyanin accumulation in mature seeds, and the seedlings of NnMYB114-OE line exhibited red pigmentation. Dual-luciferase assays confirmed that both transcription factors significantly activated the promoters of NnDFR and NnANS, indicating their crucial regulatory roles in anthocyanin biosynthesis. In this study, we screened and identified the regulatory functions of two MYB TFs in lotus anthocyanin biosynthesis, providing new insights into the molecular mechanisms underlying lotus flower coloration.
Anthocyanins are important plant pigments responsible for attractive coloration and for enhancing tolerance to various abiotic stresses. Their biosynthesis is known to be regulated by methyl jasmonate (MeJA). Although the promotive effect of MeJA on anthocyanin accumulation has been widely reported, the underlying regulatory mechanisms remain insufficiently understood. In this study, we identified an ethylene-responsive factor (ERF) family transcription factor, PcRAV2, that responds to MeJA signaling and enhances anthocyanin accumulation. PcMYB10, a central gene that positively regulates anthocyanin accumulation, was indirectly activated by PcRAV2. In addition, yeast one-hybrid library screening revealed that PcMYB108 functions upstream of PcMYB10 and acts as a negative regulator of anthocyanin biosynthesis; notably, PcMYB108 expression was suppressed by PcRAV2. Furthermore, PcRAV2 directly activated PcUFGT expression by binding to its promoter. Collectively, PcRAV2 promotes anthocyanin biosynthesis through two pathways: the PcRAV2-PcMYB108-PcMYB10 transcriptional cascade and the PcRAV2-PcUFGT regulatory pathway. These findings reveal a novel MeJA-driven regulatory pathway for anthocyanin biosynthesis in plants and provide a theoretical basis for the genetic improvement of fruit coloration in pear.
Guorong Zhang, Lei Guo, Haowei Cao et al.· Plant physiology and biochem...· 0 citations
Begonia semperflorens is an important ornamental plant worldwide, but its practical application is severely limited by low temperature sensitivity. However, the molecular regulatory mechanisms underlying low temperature-induced anthocyanin biosynthesis remain unclear. In this study, we assembled a high-quality chromosome-level B. semperflorens genome. Through genomic and MYB gene family analysis, we identified a key transcription factor BsTT2, which directly binds to the BsDFR promoter and enhances its activity, thereby driving anthocyanin accumulation in B. semperflorens. Furthermore, using BsTT2 as bait, we identified its interacting protein BsAlfin2. Under low temperature-induced reactive oxygen species (ROS) signaling, BsAlfin2 undergoes nuclear translocation and forms a complex with BsTT2, synergistically enhancing the activation of the BsDFR promoter and significantly improving anthocyanin production efficiency. Based on these results, we propose a previously uncharacterized BsAlfin2/BsTT2-BsDFR regulatory module, which reveals a molecular links low-temperature ROS signaling to anthocyanin biosynthesis in B. semperflorens. In summary, this study not only provides chromosome-level genomic resources for B. semperflorens research but also elucidates a key molecular module in low temperature-induced anthocyanin biosynthesis regulatory pathway, laying a theoretical and data foundation for future studies on leaf color improvement and stress resistance breeding in Begonia.
This study uncovers a rare case in which a deletion of just two amino acids is sufficient to generate a potent dominant-negative regulator, designated SmMYB1alf-D, which enables reliable prediction of fruit color and provides a breeding strategy to precisely manipulate anthocyanin metabolism.
Yan Li, Yiwen Tian, Wanyue Li et al.· Plant Communications· 0 citations
To elucidate the seasonal variation in flower coloration of Delphinium grandiflorum cv. F1 Super Platinum Blue, we performed transcriptome analysis and heterologous expression in Nicotiana tabacum, and molecular interaction assays. Flowers in early summer (PB1) displayed deeper blue coloration and more than 8-fold higher total anthocyanin content than those in early spring (PB2). In PB1, cyanodelphin was the major anthocyanin, whereas both cyanodelphin and violdelphin accumulated in PB2. Transcriptome data revealed that DgMYB4, an R2R3-MYB, was significantly upregulated in PB1. Ectopic expression of DgMYB4 in tobacco promoted anthocyanin accumulation and induced multiple anthocyanin-related genes. Mechanistically, yeast one-hybrid assays showed that DgMYB4 could bind the tested tobacco promoter fragments of NtANS, NtF3GT, NtF3GRhaT, and NtpHBAGT2, whereas dual-luciferase assays demonstrated DgMYB4-dependent promoter activation that was markedly enhanced by DgbHLH, particularly for NtF3GRhaT and NtpHBAGT2. Thus, our results support a model in which DgMYB4 contributes to coordinated regulation of core anthocyanin biosynthesis, downstream modification, and acyl-glucose donor-related processes. Greenhouse temperature monitoring and transcriptomic analyses revealed an association between contrasting seasonal cultivation conditions and differential DgMYB4 expression. These findings identify DgMYB4 as an important candidate regulator linking anthocyanin accumulation with downstream structural modification in Delphinium.
Fumi Suzuki, Makoto Suzawa, Chisato Isobe et al.· Plant physiology and biochem...· 0 citations
Red-fleshed peach exhibits attractive anthocyanin (AN) pigmentation but is often accompanied by undesirable proanthocyanidin (PA)-derived astringency and high fruit acidity (FA), limiting its commercial value. The genetic mechanisms underlying this co-occurrence remain unclear. Using an F1 population derived from ‘wen30’ and ‘wen48’, we identified co-localized QTLs for AN, PA, and FA within a 0.32–4.74 Mb region on chromosome 5. Integrating transcriptomics with Y1H, EMSA, and dual-luciferase assays, we demonstrated that PpBL functions as a key regulator of both AN and PA accumulation. PpBL directly activates PpUGT73C3, independently of PpMYB10.1, to promote AN biosynthesis, and enhances PA accumulation by directly upregulating PpLAR and PpANR; PpUGT73C3 also contributes to PA accumulation via an unclear mechanism. In contrast, FA is not directly regulated by PpBL but is associated with a high-acidity PpTST1 allele tightly linked to a blood-TE insertion in the PpBL promoter. The haplotype carrying both the insertion and PpUGT73C3 coding variants confers elevated AN and PA but also increased FA due to linkage drag. These findings reveal pleiotropic control of color and astringency and a linkage-based association with acidity, providing insights for peach breeding.
Hongyang Xing, Jia-Qi Fan, Gui-Zhi Li et al.· Molecular Horticulture· 0 citations
