AUTHOR=Xiang Lien , He Ping , Shu Guoping , Yuan Mingyuan , Wen Mengling , Lan Xiaozhong , Liao Zhihua , Tang Yueli 

TITLE=AabHLH112, a bHLH transcription factor, positively regulates sesquiterpenes biosynthesis in Artemisia annua

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.973591

DOI=10.3389/fpls.2022.973591

ISSN=1664-462X

ABSTRACT=<p>The bHLH transcription factors play important roles in the regulation of plant growth, development, and secondary metabolism. β-Caryophyllene, <italic>epi</italic>-cedrol, and β-farnesene, three kinds of sesquiterpenes mainly found in plants, are widely used as spice in the food industry and biological pesticides in agricultural production. Furthermore, they also have a significant value in the pharmaceutical industry. However, there is currently a lack of knowledge on the function of bHLH family TFs in β-caryophyllene, <italic>epi</italic>-cedrol, and β-farnesene biosynthesis. Here, we found that AabHLH112 transcription factor had a novel function to positively regulate β-carophyllene, <italic>epi</italic>-cedrol, and β-farnesene biosynthesis in <italic>Artemisia annua</italic>. Exogenous MeJA enhanced the expression of <italic>AabHLH112</italic> and genes of β-caryophyllene synthase (<italic>CPS</italic>), <italic>epi-</italic>cedrol synthase (<italic>ECS</italic>), and β-farnesene synthase (<italic>BFS</italic>), as well as sesquiterpenes content. Dual-LUC assay showed the activation of <italic>AaCPS, AaECS</italic>, and <italic>AaBFS</italic> promoters were enhanced by AabHLH112. Yeast one-hybrid assay showed AabHLH112 could bind to the G-box (CANNTG) <italic>cis</italic>-element in promoters of both <italic>AaCPS</italic> and <italic>AaECS.</italic> In addition, overexpression of <italic>AabHLH112</italic> in <italic>A. annua</italic> significantly elevated the expression levels of <italic>AaCPS</italic>, <italic>AaECS</italic>, and <italic>AaBFS</italic> as well as the contents of β-caryophyllene, <italic>epi</italic>-cedrol, and β-farnesene, while suppressing <italic>AabHLH112</italic> expression by RNAi reduced the expression of the three genes and the contents of the three sesquiterpenes. These results suggested that <italic>AabHLH112</italic> is a positive regulator of β-caryophyllene, <italic>epi</italic>-cedrol, and β-farnesene biosynthesis in <italic>A. annua</italic>.</p>