| Summary: | Bisabolene-type sesquiterpenoids, which have multiple bioactivities, including anticancer activity, are one of the main groups of compounds in the essential oil extracted from <i>Santalum album</i> L. and other <i>Santalum</i> species. Bisabolene synthetase (<i>SaBS</i>) is a key enzyme for the synthesis of bisabolene in <i>S. album</i>, but the regulation of the <i>SaBS</i> gene’s expression is poorly understood. In this study, a 1390-bp promoter sequence of the <i>SaBS</i> gene was isolated from the leaves of six-year-old <i>S. album</i>. A bioinformatics analysis showed that certain environment stresses and phytohormone-activated <i>cis</i>-acting elements were distributed in different regions of the <i>SaBS</i> promoter (P<i>SaBS</i>). Transgenic Arabidopsis carrying full-length P<i>SaBS</i> had significantly higher β-glucuronidase (GUS) activity than the untreated control after treatment with salicylic acid (SA), suggesting that P<i>SaBS</i> is a SA-inducible promoter. Histochemical GUS staining and GUS fluorometric assays of transgenic Arabidopsis showed that the GUS activity directed by P<i>SaBS</i> was mainly expressed in stem tissue, followed by leaves and flowers. Moreover, different regions of P<i>SaBS</i> showed significantly different GUS activity. A 171-bp fragment upstream of the transcriptional initiation codon (ATG) is the core promoter region of P<i>SaBS</i>. Our results provide insight into and a greater understanding of the transcriptional regulation mechanism of the <i>SaBS</i> gene, which could serve as an alternative inducible promoter for transgenic plant breeding.
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