次生代谢产物是药用植物的主要有效成分，也是决定中药材品质的物质基础。NO是植物中一种重要信号分子。前期研究结果表明，UVB等环境因子通过激活植物细胞中NO信号途径促进次生产物合成，提示NO是药用植物次生代谢的潜在调控位点。最近，我们发现NIA1基因表达上调是介导UVB触发植物内源NO迸发的主要机制。在此基础上，提出通过调控NIA1基因表达，激活药用植物细胞中NO信号途径促进次生产物合成的研究设想。拟以银杏为材料，构建转NIA1基因细胞，考查NIA1基因对银杏黄酮、萜类等次生产物含量及GbF3H、GbFLS、GbMVD等次生代谢基因表达水平的影响，验证本项目的研究设想。同时，通过考察NIA1基因对胞内NO、JA等信号分子的激活作用以及不同信号分子在介导NIA1诱发次生产物合成中的功能及cross-talk机制，解析NIA1基因的作用机理。研究结果将为药用植物次生代谢分子调控提供一种新的策略。

Secondary metabolites are the main bioactive substances of medical plants. Nitric oxide (NO) is an important signaling molecule in plants. Previous studies showed that environmental factors such as UVB radiation may stimulate biosynthesis of secondary metabolites in plants by triggering NO signaling, which suggests that NO might be a potential target for controlling secondary metabolism in medical plants. Recently, we found that NIA1 gene is responsible for UVB-triggered NO burst in Betula pendula leaves. Based on the previous findings, we proposed that overexpression of NIA1 gene in medical plants may stimulate secondary metabolite biosynthesis by triggering endogenous NO signaling. In this project, we plan to generate transgenic Ginkgo Biloba L. overexpressing NIA1 protein under the estradiol-inducible promoter and assay the effects of NIA1 on contents of flavonoids and terpenoids and expression levels of the genes in terpenoid and flavonoid biosynthetic pathways such as GbCHS、GbF3H、GbFLS、GbHMGR and GbMVD. Furthermore, the effects of NIA1 on nitrate reductase (NR) activity and endogenous NO levels in Ginkgo Biloba will be determined to check if overexpression of NIA1 could induce NR activity and trigger NO burst. The roles of NR and NO signaling in NIA1-induced terpenoid and flavonoid biosynthesis will also be investigated by examining the effects of NR inhibitors and NO specific scavenger on the contents of terpenoids and flavonoids and the expression levels of the genes in terpenoid and flavonoid biosynthetic pathways in transgenic ransgenic Ginkgo Biloba. The functions of other signaling molecules such as jasmonic acid (JA), reactive oxygen species (ROS) and protein kinase and their cross-talking in mediating NIA1-inudced terpenoid and flavonoid biosynthesis will also be studied.