AUTHOR=Yang Jiahui , Chen Yicun , Gao Ming , Wu Liwen , Xiong Shifa , Wang Siqi , Gao Jing , Zhao Yunxiao , Wang Yangdong 

TITLE=Comprehensive identification of bHLH transcription factors in Litsea cubeba reveals candidate gene involved in the monoterpene biosynthesis pathway

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1081335

DOI=10.3389/fpls.2022.1081335

ISSN=1664-462X

ABSTRACT=<p><italic>Litsea cubeba</italic> (Lour.) Person, an economically important aromatic plant producing essential oils, has lemon-like fragrance and 96.44–98.44% monoterpene contents. bHLH transcription factor plays an important role in plant secondary metabolism and terpene biosynthesis. In this study, we used bioinformatics to identify bHLH transcription factors in <italic>L. cubeba</italic>, 173 <italic>bHLH</italic> genes were identified from <italic>L. cubeba</italic> and divided these into 26 subfamilies based on phylogenetic analysis. The majority of bHLHs in each subfamily shared comparable structures and motifs. While <italic>LcbHLHs</italic> were unevenly distributed across 12 chromosomes, 10 tandem repeats were discovered. Expression profiles of bHLH genes in different tissues demonstrated that <italic>LcbHLH78</italic> is a potential candidate gene for regulating monoterpene biosynthesis. <italic>LcbHLH78</italic> and the terpene synthase <italic>LcTPS42</italic> showed comparable expression patterns in various tissues and fruit development stages of <italic>L. cubeba</italic>. Subcellular localization analysis revealed that LcbHLH78 protein localizes to the nucleus, consistent with a transcription factor function. Importantly, transient overexpression of <italic>LcbHLH78</italic> increased geraniol and linalol contents. Our research demonstrates that <italic>LcbHLH78</italic> enhances terpenoid biosynthesis. This finding will be beneficial for improving the quality of <italic>L. cubeba</italic> and provides helpful insights for further research into the control mechanism of <italic>LcbHLH</italic> genes over terpenoid biosynthesis.</p>