Functional characterization of a liverworts bHLH transcription factor involved in the regulation of bisbibenzyls and flavonoids biosynthesis

Abstract

BackgroundThe basic helix-loop-helix (bHLH) transcription factors (TFs), as one of the largest families of TFs, play important roles in the regulation of many secondary metabolites including flavonoids. Their involvement in flavonoids synthesis is well established in vascular plants, but not as yet in the bryophytes. In liverworts, both bisbibenzyls and flavonoids are derived through the phenylpropanoids pathway and share several upstream enzymes.ResultsIn this study, we cloned and characterized the function of PabHLH1, a bHLH family protein encoded by the liverworts species Plagiochasma appendiculatum. PabHLH1 is phylogenetically related to the IIIf subfamily bHLHs involved in flavonoids biosynthesis. A transient expression experiment showed that PabHLH1 is deposited in the nucleus and cytoplasm, while the yeast one hybrid assay showed that it has transactivational activity. When PabHLH1 was overexpressed in P. appendiculatum thallus, a positive correlation was established between the content of bibenzyls and flavonoids and the transcriptional abundance of corresponding genes involved in the biosynthesis pathway of these compounds. The heterologous expression of PabHLH1 in Arabidopsis thaliana resulted in the activation of flavonoids and anthocyanins synthesis, involving the up-regulation of structural genes acting both early and late in the flavonoids synthesis pathway. The transcription level of PabHLH1 in P. appendiculatum thallus responded positively to stress induced by either exposure to UV radiation or treatment with salicylic acid.ConclusionPabHLH1 was involved in the regulation of the biosynthesis of flavonoids as well as bibenzyls in liverworts and stimulated the accumulation of the flavonols and anthocyanins in Arabidopsis.

Flavonoids Accumulation in Fruit Peel and Expression Profiling of Related Genes in Purple (Passiflora edulis f. edulis) and Yellow (Passiflora edulis f. flavicarpa) Passion Fruits

“…The differential accumulation of flavonoid-related metabolites in both passion fruit cultivars was not only related to enzymatic activity but also structural gene expressions. According to previous studies, it was also related to some transcription factors such as MYB [57], BHLH [58], and WD40 [59], regulation of microRNA during protein expression and, ubiquitination and phosphorylation during protein activation [60].…”

Systematic Analysis of bHLH Transcription Factors in Cassava Uncovers Their Roles in Postharvest Physiological Deterioration and Cyanogenic Glycosides Biosynthesis

“…As well, many previous reports showed that flavonoids synthesized in plant could effectively eliminate ROS to enhance the tolerance in adverse environment ( Wang et al, 2016 ; Qin et al, 2020 ). Interestingly, some bHLHs were confirmed to be associated with flavonoids synthesis ( Zhao et al, 2019 ; Aslam et al, 2020 ) and belongs to subfamilies 2 ( Guan et al, 2013 ; Geng and Liu, 2018 ; Geng et al, 2019 ; Waseem et al, 2019 ; Zhao R. et al, 2020 ). Especially, experimental data showed that bHLHs bound to the promoter of antioxidant genes such as POD, SOD through E-box or G-box ( Liu et al, 2013 ; Geng and Liu, 2018 ).…”

Integrative Analysis of the Transcriptome and Metabolome Reveals Genes Involved in Phenylpropanoid and Flavonoid Biosynthesis in the Trapa bispinosa Roxb.

“…Previous studies have demonstrated that multiple TFs regulate phenylpropanoid and flavonoid biosynthesis in plants. MYB ( Ma et al, 2018 ; Tang et al, 2021 ), bHLH ( Zhao et al, 2019 ), and WD40 ( Mol et al, 2021 ), ate the most important TFs, while NAC ( Yang et al, 2019 ), WRKY ( Joshi et al, 2022 ), and bZIP ( An et al, 2018 ) are the least important. In this study, 27 transcription factors that may play a role in the biosynthesis of phenylpropane or flavonoids were identified.…”