Hypericum perforatum L. (St. John’s wort) is a well-known medicinal plant that possesses secondary metabolites with beneficial pharmacological properties. However, improvement in the production of secondary metabolites via genetic manipulation is a challenging task as H. perforatum remains recalcitrant to Agrobacterium tumefaciens-mediated transformation. Here, the transcripts of key genes involved in several plant defence responses (secondary metabolites, RNA silencing, reactive oxygen species (ROS) and specific defence genes) were investigated in H. perforatum suspension cells inoculated with A. tumefaciens by quantitative real-time PCR. Results indicated that key genes from the xanthone, hypericin and melatonin biosynthesis pathways, the ROS-detoxification enzyme HpAOX, as well as the defence genes Hyp-1 and HpPGIP, were all upregulated to rapidly respond to A. tumefaciens elicitation in H. perforatum. By contrast, expression levels of genes involved in hyperforin and flavonoid biosynthesis pathways were markedly downregulated upon A. tumefaciens elicitation. In addition, we compared the expression patterns of key genes in H. perforatum leaf tissues with and without dark glands, a major site of secondary metabolite production. Overall, we provide evidence for the upregulation of several phenylpropanoid pathway genes in response to elicitation by Agrobacterium, suggesting that production of secondary metabolites could modulate H. perforatum recalcitrance to A. tumefaciens-mediated transformation.

贯叶连翘（圣约翰草）是一种众所周知的药用植物，具有具有有益药理特性的次生代谢产物。然而，通过基因操作改进次生代谢物的生产是一项具有挑战性的任务，因为贯叶连翘仍然难以接受根癌农杆菌介导的转化。在这里，在接种根癌土壤杆菌的贯叶连翘悬浮细胞中研究了参与几种植物防御反应（次级代谢产物、RNA 沉默、活性氧 (ROS) 和特定防御基因）的关键基因的转录本通过实时定量 PCR。结果表明，来自呫吨酮、金丝桃素和褪黑激素生物合成途径的关键基因、ROS 解毒酶HpAOX以及防御基因Hyp - 1和HpPGIP均上调，以快速响应H. perforatum 中根癌土壤杆菌的诱导。相比之下，参与金丝桃素和类黄酮生物合成途径的基因的表达水平在根癌农杆菌诱导后显着下调。此外，我们比较了贯叶连翘中关键基因的表达模式有和没有暗腺体的叶组织，次生代谢物产生的主要场所。总体而言，我们提供了响应农杆菌引发的几种苯丙烷途径基因上调的证据，表明次生代谢物的产生可以调节贯叶连翘对根癌农杆菌介导的转化的抵抗。