Combination Of Transcriptome And Metabolome Analysis Of Key Metabolic Pathways In Halenia Elliptica D. Don Responding To Altitude Change

As one of the important Chinese and Tibetan medicinal materials,Halenia elliptica D.Don is commonly used to treat liver and gallbladder diseases,and is widely distributed in the Qinghai-Tibet Plateau.As an important topographic factor,elevation has an important impact on the growth of plants,and plants can produce adaptive changes to different altitude environments.Exploring the adaptation mechanisms of H.elliptica to altitude gradients can provide theoretical reference for the optimal distribution area.In this study,H.elliptica at different altitudes was used as the experimental material to reveal the key metabolic pathway of H.elliptica in response to environmental changes through the combined analysis of transcriptomics and metabonomics.The main results are as follows:1.The effect of altitude on the expression of gene in H.elliptica was studied by transcriptome analysis.A total of 279 190 Unigenes and 179 960 functional annotations were obtained by transcriptional sequencing and assembly.There are 178480 Unigenes commented to the Nr database,87 377 Unigenes commented to the KEGG database and 29 201 Unigenes comment to the GO database.In the comparison of different altitudes,there are 47 differential genes between HM-1 vs HM-2,including 36 up-regulated genes and 11 down-regulated genes;There are 448 differential genes between HM-1 and HM-3,including 263 up-regulated genes and185 down-regulated genes.It shows that the altitude gradient has a certain effect on genes expression,and there were significant difference in the number of differential genes among different altitude gradients.Through KEGG enrichment analysis,the differential genes were enriched in endoplasmic reticulum protein processing,Longevity regulating pathway,Apoptosis,Protein processing in endoplasmic reticulum,Melanogenesis pathways.2.Untargeted metabonomics was used to study the changes of metabolites in H.elliptica at different altitude gradients.The results showed that 149 commensal metabolites were detected in 6 groups of 4 sample points,including 70 in the positive ion mode and 79 in the negative ion mode.KEGG enrichment analysis of differential metabolites showed that differential metabolites were mainly enriched in Flavonoid biosynthesis,Phenylpropane biosynthesis,Flavonoid and flavonol biosynthesis,Citric acid cycle,Tryptophan metabolism and other pathways.3.The combined analysis results of transcriptomics and metabolomics showed that there were 15 metabolic pathways co-enriched by gene expression and metabolites,including phenylpropanoid biosynthesis,amino acid metabolism,nucleotide metabolism and carbohydrate metabolism.As for H.elliptica,it was found that the phenylpropane biosynthesis pathway was related to the antioxidant activity and growth and development.The amino acid metabolism pathway responded to the low-temperature and low-oxygen environment by increasing the respiration and auxin content.Carbohydrate metabolism provides energy in the high altitude environments.The nucleotide metabolism pathway is related to coping with strong radiation and low temperature stress.These are the main physiological regulatory mechanisms of H.elliptica in response to environmental changes at different altitude gradients.