grape bHLH transcription factor gene, VvbHLH1, increases the accumulation of flavonoids and enhances salt and drought tolerance in transgenic Arabidopsis thaliana

In plants, transcriptional regulation is the most important tool for modulating flavonoid biosynthesis. The basic helix-loop-helix transcription factors are only one example how then flavonoid pathway is regulated. There are other transcription factors as well. In this study, the codon-optimized VvbHLH1 gene from grape was chemically synthesized. Overexpression of VvbHLH1 significantly increased the accumulation of flavonoids and enhanced salt and drought tolerance in transgenic Arabidopsis thaliana plants. Real-time quantitative PCR analysis showed that overexpression of VvbHLH1 resulted in the up-regulation of genes involved in flavonoid biosynthesis, abscisic acid (ABA) signaling pathway, proline biosynthesis, stress responses and ROS scavenging under salt and drought stresses. Further analyses under salt and drought stresses showed significant increases of ABA and proline content, superoxide dismutase and peroxidase activities, as well as significant reduction of hydrogen peroxide (H₂O₂) and malonaldehyde content. The results demonstrate the explicit role of VvbHLH1 in conferring salt and drought tolerance by increasing the accumulation of flavonoids and ABA signalling in transgenic A. thaliana. The VvbHLH1 gene has the potential to be used to increase the content of valuable flavonoids and improve the tolerance to abiotic stresses in A. thaliana and other plants.