Birch (Betula platyphylla) contains triterpenoids with anti-HIV and anti-tumor activities. However, the natural amount of these triterpenoids is low, and their chemical synthesis, costly. Transcription factors, such as the bHLH (basic helix-loop-helix), can regulate metabolite pathways, and improve yield. Thus, transcription factors can potentially improve production of birch triterpenoids.

The team of Jing Yin from Northeast Forestry University in China studied two genes, BpMYC4 and BpbHLH9, which encode bHLH transcription factors in birch. The expressions of BpMYC4 and BpbHLH9 were found to be increased with treatments of abscisic acid, methyl jasmonate, and gibberellin while it is decreased by ethephon treatment.

The BpbHLH9 gene was then attached to an improved promoter and introduced to birch. Compared to wild types, the resulting transgenic birch exhibited upregulated expression of genes related to triterpenoid synthesis.

These findings will be the groundwork for the development of birch accessions with improved triterpenoid production.

For more information, read the article in BMC Plant Biology.

Figure: Neighbor-joining phylogenetic tree of BpMYC4 from Betula platyphyll and other bHLHs constructed using MEGA 6.0 software. The scale bar represents 0.05 amino acid substitutions per site