Résumé
ObjectiveTo study the changing characteristics of secondary metabolic compounds accumulated in Dendrobium nobile stems at different growth years， a simulated wild stone plant， in order to provide a theoretical basis for rational planning of the harvesting period of D. nobile. MethodUltra-high performance liquid chromatography-mass spectrometry（UPLC-MS/MS） was used to detect and analyze the secondary metabolites in the stems of 1-year-old， 2-year-old， and 3-year-old D. nobile. The mass spectrometry data were processed using Analyst 1.6.3 software， and all samples were subjected to principal component analysis（PCA）， cluster heat map analysis， partial least squares-discriminant analysis（PLS-DA）， and differential secondary metabolites were screened based on variable importance in projection（VIP） values>1， fold change（FC）≥2 and FC≤0.5. Then differential secondary metabolites were identified based on relative molecular weight， fragmentation ions and mass spectrometry database， and enriched pathways were identified based on the Kyoto Encyclopedia of Genes and Genomes（KEGG） database. ResultA total of 1 317 secondary metabolites were identified in the stems of D. nobile at three growth stages， with flavonoids， phenolic acids， alkaloids and terpenoids accounting for 76.55% of the total. Compared with the 1-year-old stems of D. nobile， 289 differential secondary metabolites were identified in the 2-year-old stems， of which 255 were up-regulated and 34 were down-regulated， 682 differential secondary metabolites were identified in the 3-year-old stems， of which 502 were up-regulated and 180 were down-regulated. Compared to the 2-year-old stems， the 3-year-old stems had 602 differential secondary metabolites， with 405 up-regulated and 197 down-regulated. As the growth stage of D. nobile increased， the top 10 up-regulated differential metabolites mainly included flavonoids， phenolic acids， phenylpropanoids and terpenoids， such as kaempferol derivatives， asperulosidic acid， apigenin derivatives， chrysoeriol derivatives， isorhamnetin derivatives， taxifolin derivatives， quercetin derivatives. KEGG enrichment analysis showed significant enrichment of secondary metabolites in the flavonoid biosynthesis， flavone， and flavonol biosynthesis， secondary metabolite biosynthesis， and phenylpropanoid biosynthesis pathways with the increase of growth years. ConclusionWith the increase of the growth years， the levels of secondary metabolites such as flavonoids， phenolic acids， phenylpropanoids and terpenoids in the wild-grown D. nobile have been significantly enhanced. In practical production， grading based on different growth years can be carried out to improve the medicinal and economic values of D. nobile.
Résumé
A novel method for quickly cloning genes with multiple DNA fragments--one step cloning technique using isoschizomer-heterotail restriction endonuclease (IHRE) is described. Up to six DNA segments are ligated by using only one restriction endonuclease in this method. Comparing with routine method,it is simple, fast, economical and generates products with higher purity and achievement. Light chain of human enterokinase, DNA multi-epitope vaccine to HSV2 have been designed and successfully constructed via this method.