Dataset Information

Transcription factor VvibHLH93 negatively regulates proanthocyanidin biosynthesis in grapevine.

ABSTRACT: Proanthocyanidins (PAs) derived from grape berries determine the astringency and bitterness of red wines. The two leucoanthocyanidin reductases (VviLAR1 and VviLAR2) are crucial for PA accumulation in grapevine. Our previous studies show that the promoter of VviLAR1 contains multiple proposed bHLH transcription factor binding sites, but the corresponding bHLH family regulators remain unknown. Here we identified and functionally characterized VvibHLH93 as a new bHLH transcription factor in PA pathway. Yeast one-hybrid and electrophoretic mobility shift assays showed that VvibHLH93 bound the E/G-box in VviLAR1 promoter. And VvibHLH93 gene was mainly expressed in grape flowers, tendrils, stems and berries at PA active stages. Overexpression of VvibHLH93 suppressed PA accumulation in grape callus, which was linked to the repression of the transcript levels of two VviLARs. The gene expression analysis in transgenic grape callus and the dual-luciferase assay in tobacco leaves together revealed that VvibHLH93 targeted a broad set of structural genes and transcription factors in flavonoid pathway. This research enriches the regulatory mechanism of the two VviLAR genes, and provides new insights into regulating PA content in grape berries.

SUBMITTER: Cheng J

PROVIDER: S-EPMC9449495 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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Transcription factor VvibHLH93 negatively regulates proanthocyanidin biosynthesis in grapevine.

Cheng Jing J Shi Ying Y Wang Jun J Duan Changqing C Yu Keji K

Frontiers in plant science 20220824

Proanthocyanidins (PAs) derived from grape berries determine the astringency and bitterness of red wines. The two leucoanthocyanidin reductases (VviLAR1 and VviLAR2) are crucial for PA accumulation in grapevine. Our previous studies show that the promoter of <i>VviLAR1</i> contains multiple proposed bHLH transcription factor binding sites, but the corresponding bHLH family regulators remain unknown. Here we identified and functionally characterized VvibHLH93 as a new bHLH transcription factor in ...[more]

PMID: 36092430

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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

Transcription factor VvibHLH93 negatively regulates proanthocyanidin biosynthesis in grapevine.

Publications

Transcription factor VvibHLH93 negatively regulates proanthocyanidin biosynthesis in grapevine.

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