AUTHOR=Zhang Feicui , Kong Congcong , Ma Zhenmin , Chen Wenchao , Li Yue , Lou Heqiang , Wu Jiasheng 

TITLE=Molecular characterization and transcriptional regulation analysis of the Torreya grandis squalene synthase gene involved in sitosterol biosynthesis and drought response

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1136643

DOI=10.3389/fpls.2023.1136643

ISSN=1664-462X

ABSTRACT=<p>The kernel of <italic>Torreya grandis</italic> cv. ‘Merrillii’ (Cephalotaxaceae) is a rare nut with a variety of bioactive compounds and a high economic value. β-sitosterol is not only the most abundant plant sterol but also has various biological effects, such as antimicrobial, anticancer, anti-inflammatory, lipid-lowering, antioxidant, and antidiabetic activities. In this study, a squalene synthase gene from <italic>T. grandis</italic>, <italic>TgSQS</italic>, was identified and functionally characterized. <italic>TgSQS</italic> encodes a deduced protein of 410 amino acids. Prokaryotic expression of the TgSQS protein could catalyze farnesyl diphosphate to produce squalene. Transgenic <italic>Arabidopsis</italic> plants overexpressing <italic>TgSQS</italic> showed a significant increase in the content of both squalene and β-sitosterol; moreover, their drought tolerance was also stronger than that of the wild type. Transcriptome data from <italic>T. grandis</italic> seedlings showed that the expression levels of sterol biosynthesis pathway-related genes, such as <italic>HMGS</italic>, <italic>HMGR</italic>, <italic>MK</italic>, <italic>DXS</italic>, <italic>IPPI</italic>, <italic>FPPS</italic>, <italic>SQS</italic>, and <italic>DWF1</italic>, increased significantly after drought treatment. We also demonstrated that TgWRKY3 directly bound to the <italic>TgSQS</italic> promoter region and regulated its expression through a yeast one-hybrid experiment and a dual luciferase experiment. Together, these findings demonstrate that <italic>TgSQS</italic> has a positive role in β-sitosterol biosynthesis and in protecting against drought stress, emphasizing its importance as a metabolic engineering tool for the simultaneous improvement of β-sitosterol biosynthesis and drought tolerance.</p>