Cloning and developmental expression analysis of a basic helix loop helix transcription factor gene for epigallocatechin-3-gallate biosynthesis in tea plant (Camellia sinensis L.)

摘要

Epigallocatechin-3-gallate (EGCG) is the most effective active tea polyphenol, with a wide usage in food and medicine. Basic helix-loop-helix (bHLH) transcription factors play an important role in the regulation of flavonoid biosynthesis, but it remains unclear how the bHLH gene regulates the EGCG biosynthesis in the tea plant. We isolated and cloned the full-length bHLH gene from Camellia sinensis (CS_bHLH), which is 1,599 bp in length, and encodes a 379 amino acid protein of predicted molecular weight of 41.69 kDa. Bioinformatics analysis showed that the encoded protein is acidic, hydrophilic, unstable, and without the signal peptide. Its secondary structure mainly consists of random coils (70.2%) and a-helixes (22.4%). It shares 68.97% protein sequence identity with bHLH from other plants. The EGCG content of '1005' exceeded that of its parent cultivars in the shoot and second leaf, and that's up to 12.48% in shoot of '1005'. Comparing the expression level of CS_bHLH and the EGCG content at different developmental stages of three cultivars, it was found a similar trend for each cultivar: bud second leaf fourth leaf For the samples of each cultivar, the higher the EGCG content, the higher the CS_bHLH expression level. That revealed that CS_bHLH may positively regulate the biosynthesis of EGCG.