Table_1_Functional Characterization of Serotonin N-Acetyltransferase Genes (SNAT1/2) in Melatonin Biosynthesis of Hypericum perforatum.XLS

Hypericum perforatum is a traditional medicinal plant that contains various secondary metabolites. As an active component in H. perforatum, melatonin plays important role in plant antioxidation, growth, and photoperiod regulation. Serotonin N-acetyltransferase (SNAT) is the key enzyme involved in the last or penultimate step of phytomelatonin biosynthesis. A total of 48 members of SNAT family were screened and analyzed based on the whole genome data of H. perforatum, and two SNAT genes (HpSNAT1 and HpSNAT2) were functionally verified to be involved in the biosynthesis of melatonin. It was found that HpSNAT1 and HpSNAT2 were highly expressed in the leaves and showed obvious responses to high salt and drought treatment. Subcellular localization analysis indicated that these two proteins were both localized in the chloroplasts by the Arabidopsis protoplasts transient transfection. Overexpression of HpSNAT1 and HpSNAT2 in Arabidopsis (SNAT) and H. perforatum (wild-type) resulted in melatonin content 1.9–2.2-fold and 2.5–4.2-fold higher than that in control groups, respectively. Meanwhile, SNAT-overexpressing Arabidopsis plants showed a stronger ability of root growth and scavenging endogenous reactive oxygen species. In this study, the complete transgenic plants of H. perforatum were obtained through Agrobacterium-mediated genetic transformation for the first time, which laid a significant foundation for further research on the function of key genes in H. perforatum.

Hypericum perforatum，即刺芹黄连，为传统药用植物，富含多种次生代谢产物。其中，褪黑素作为H. perforatum的活性成分，在植物抗氧化、生长以及光周期调节中发挥着至关重要的作用。血清素N-乙酰转移酶（Serotonin N-acetyltransferase，SNAT）是参与植物褪黑素生物合成最后或倒数第二步的关键酶。基于刺芹黄连的全基因组数据，筛选并分析了SNAT家族的48个成员，其中两个SNAT基因（HpSNAT1和HpSNAT2）经过功能验证，参与了褪黑素的生物合成。研究发现，HpSNAT1和HpSNAT2在叶片中高度表达，并对高盐和干旱处理表现出明显的响应。亚细胞定位分析表明，这两种蛋白质通过拟南芥原生质体瞬时转染均定位于叶绿体中。在拟南芥（SNAT）和刺芹黄连（野生型）中过表达HpSNAT1和HpSNAT2，其褪黑素含量分别比对照组高出1.9至2.2倍和2.5至4.2倍。同时，SNAT过表达的拟南芥植株表现出更强的根系生长和清除内源性活性氧的能力。本研究首次通过农杆菌介导的遗传转化获得了刺芹黄连的完整转基因植株，为深入研究刺芹黄连关键基因的功能奠定了重要基础。