MYB Transcription Factors Negatively Regulate StL3OH in Salt Stress Response of Schizonepeta tenuifolia

Salt stress affects the growth, quality, and secondary metabolism of medicinal plants, but its effects on essential oil biosynthesis in Schizonepeta tenuifolia remain unclear. In this study, a salt stress model was established for Schizonepeta tenuifolia (Benth.) Briq. to investigate changes in growth, monoterpenoid accumulation, non-targeted metabolism, and transcriptional profiles. To further clarify the regulatory mechanism of monoterpenoids biosynthesis, the MYB family members were identified at the genome-wide level, and candidate regulators were screened based on the expression patterns and promoter features of StL3OH (limonene -3-hydroxylase). Among them, StMYB71 and StMYB8774 were identified as candidate regulators of monoterpene biosynthesis. Functional analysis indicated that both transcription factors negatively regulated StL3OH expression by binding to the MYBHv1 cis-element in its promoter. These findings improve our understanding of the salt stress response and transcriptional regulation of monoterpene biosynthesis in S. tenuifolia and provide a basis for the future improvement of Schizonepetae Herba quality and salt tolerance.