Response of leaf blade in Zanthoxylum planispinum var. dintanensis to differences altitudes through integrated metabolomics and transcriptomics analysis

Abstract

To analyze the effects of altitude on Z. planispinum var. Dintanensisin, leaves of samples from different altitudes (H1:1054 m.a.s.l., H2:821 m.a.s.l., H3:645 m.a.s.l.) were collected for integrative analysis of the metabolome and transcriptome in the present study. According to transcriptome data, a total of 9,566 differentially expressed genes (DEGs) were identified from the three sample comparisons (H1 vs. H2, H1 vs. H3, H2 vs. H3). Fewer DEGs were observed in the H2 vs. H3 group than in the other two comparison groups, suggesting that differences in the transcriptome increased with elevation. Most genes were involved in “Biosynthesis of secondary metabolites”, “Plant hormone signal transduction” and “MAPK signaling pathway-plant” based on KEGG enrichment analysis. In total, 423 differential metabolites (DAMs) were determined in the three comparisons (mentioned above) by using metabolomics analysis, of which flavonoids (14.91%) were dominant. Interestingly, more accumulation of terpenoids, aldehydes and esters was observed at higher altitudinal levels, while higher percentages of flavonoids and polyphenols were obtained at lower altitudes based upon K-Means analysis. A unique pathway (p value<0.01) linked to “flavonoid biosynthesis” appeared to have consistent expression patterns in the comparison of H1 vs. H3 based on network analyses of DEGs and DAMs. Notably, regarding the direct products of catalytic reactions, naringenin chalcone, aromadendrin, and naringenin were positively regulated by genes encoding CHS, F3H and CHI, respectively. In addition, the transcription levels of nine candidate genes, including CHI, CHS, CCoAOMT, 2ODDs, ANS, ANR, F3H, DFR and HCT, were confirmed by RT‒qPCR, which were consistent with transcriptional profile data regarding RNA-seq and further demonstrated that these genes involved in flavonoid biosynthesis contribute to the environmental adaptation of the blade in Z. planispinum var. Dintanensis. In summary, our findings represent the first integration of transcriptome data with widely targeted metabolomic data from Z. planispinum var. Dintanensis grown in rocky desertification control areas, which provides novel insights into adaptation to environmental stress. This study has the potential to improve the cultivation and management of Z. planispinum var. Dintanensis through various technologies to gain maximum medicinal production in the future.