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SmbHLH37 Functions Antagonistically With SmMYC2 in Regulating Jasmonate-Mediated Biosynthesis of Phenolic Acids in Salvia miltiorrhiza.

ABSTRACT: Jasmonates (JAs) are integral to various defense responses and induce biosynthesis of many secondary metabolites. MYC2, a basic helix-loop-helix (bHLH) transcription factor (TF), acts as a transcriptional activator of JA signaling. MYC2 is repressed by the JASMONATE ZIM-domain (JAZ) proteins in the absence of JA, but de-repressed by the protein complex SCFCOI1 on perception of JA. We previously reported that overexpression of SmMYC2 promotes the production of salvianolic acid B (Sal B) in Salvia miltiorrhiza. However, the responsible molecular mechanism is unclear. Here, we showed that SmMYC2 binds to and activates the promoters of its target genes SmTAT1, SmPAL1, and SmCYP98A14 to activate Sal B accumulations. SmbHLH37, a novel bHLH gene significantly up-regulated by constitutive expression of SmMYC2, was isolated from S. miltiorrhiza for detailed functional characterization. SmbHLH37 forms a homodimer and interacts with SmJAZ3/8. Overexpression of SmbHLH37 substantially decreased yields of Sal B. SmbHLH37 binds to the promoters of its target genes SmTAT1 and SmPAL1 and blocks their expression to suppress the pathway for Sal B biosynthesis. These results indicate that SmbHLH37 negatively regulates JA signaling and functions antagonistically with SmMYC2 in regulating Sal B biosynthesis in S. miltiorrhiza.

SUBMITTER: Du T

PROVIDER: S-EPMC6262058 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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SmbHLH37 Functions Antagonistically With SmMYC2 in Regulating Jasmonate-Mediated Biosynthesis of Phenolic Acids in Salvia miltiorrhiza.

Du Tangzhi T Niu Junfeng J Su Jiao J Li Shasha S Guo Xiaorong X Li Lin L Cao Xiaoyan X Kang Jiefang J

Frontiers in plant science 20181122

Jasmonates (JAs) are integral to various defense responses and induce biosynthesis of many secondary metabolites. MYC2, a basic helix-loop-helix (bHLH) transcription factor (TF), acts as a transcriptional activator of JA signaling. MYC2 is repressed by the JASMONATE ZIM-domain (JAZ) proteins in the absence of JA, but de-repressed by the protein complex SCFCOI1 on perception of JA. We previously reported that overexpression of SmMYC2 promotes the production of salvianolic acid B ...[more]

PMID: 30524467

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Project description:IntroductionSalvia miltiorrhiza is a renowned traditional Chinese medicinal plant with extremely high medicinal value, especially for cardiovascular and cerebrovascular diseases. The jasmonic acid (JA) signaling pathway plays an important role in the improved biosynthesis of secondary metabolites, which is mediated by a major transcriptional regulator, MYC2. However, the JA regulatory mechanism of secondary metabolites biosynthesis in S. miltiorrhiza is still largely unknown.ObjectivesOur work focuses on the dissection of the molecular mechanism of transcriptional regulation in MeJA-mediated biosynthesis of medicinal components of S. miltiorrhiza. We examined the role of MeJA-responsive bHLH transcription factors (TFs) in improving bioactive secondary metabolites accumulation in S. miltiorrhiza.MethodsHairy root transformation based on CRISPR/Cas9 technique was used to decipher gene function(s). Changes in the content of phenolic acids were evaluated by HPLC. Y1H, EMSA and dual-LUC assays were employed to analyze the molecular mechanism of SmbHLH60 in the regulation on the biosynthesis of phenolic acids and anthocyanins. Y2H, BiFC and pull-down affinity assays were used to corroborate the interaction between SmbHLH60 and SmMYC2.ResultsBeing one of the most significantly negatively regulated bHLH genes by MeJA, a new transcription factor SmbHLH60 was discovered and characterized. Over-expression of SmbHLH60 resulted in significant inhibition of phenolic acid and anthocyanin biosynthesis in S. miltiorrhiza by transcriptionally repressing of target genes such as SmTAT1 and SmDFR, whereas CRISPR/Cas9-generated knockout of SmbHLH60 resulted in the opposite effect. In addition, SmbHLH60 and SmMYC2 formed a heterodimer to antagonistically regulate phenolic acid and anthocyanin biosynthesis.ConclusionOur results clarified that SmbHLH60 is a negativeregulator on the biosynthesis of phenolic acids and anthocyanins. SmbHLH60 competed with SmMYC2 in an antagonistic manner, providing new insights for the molecular mechanism of MeJA-mediated regulation on the biosynthesis of secondary metabolites in S. miltiorrhiza.

Dataset Information

SmbHLH37 Functions Antagonistically With SmMYC2 in Regulating Jasmonate-Mediated Biosynthesis of Phenolic Acids in Salvia miltiorrhiza.

Publications

SmbHLH37 Functions Antagonistically With SmMYC2 in Regulating Jasmonate-Mediated Biosynthesis of Phenolic Acids in <i>Salvia miltiorrhiza</i>.

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