Saccharide production and its molecular regulation in response to multiple stresses in Dendrobium nobile

The saccharide content is one of the most important indicators for the quality evaluation of the Shihu herb ( Dendrobium nobile Lindl.). To fully understand saccharide production in this medicinal plant, an integrated metabolic and transcriptomic method was employed for analysis. The contents of total saccharides, non-phosphorylated saccharides, and hexose saccharides were mainly induced by low temperature and drought, while they were suppressed by dark and ultraviolet stresses. There were 44 saccharides and saccharide derivatives showed a significant stress response in Dendrobium nobile . Following genome-wide association and protein-protein interaction, a total of 182 genes were identified to participate in the core regulation of saccharide production. Based on these differentially accumulated saccharides and differentially expressed genes, a saccharide biosynthesis map was then constructed. From this map, the saccharide production was mainly improved by enhancing carbon fixation and return. Finally, a complete regulatory network from environmental stresses to saccharide accumulation was further deduced, including stress recognition ( DnHSP70s , DnUVR8 , and DnCOR413PM2 ), signal transduction ( DnTMK1 , DnCDKB1–1 , and DnHFLX ), transcriptional regulation ( DnPTI6 , DnSRM1L , DnNAC3 ), genetic information processing ( DnRPLs and DnRPSs ), post-translational regulation ( DnDNAJs ), photosynthesis ( DnMPUHL1 , DnPSA3C , and DnRAF1C ), carbon fixation ( DnRBCS512 and DnPPCK ), return of down-stream metabolites ( DnPEELs , DnCHNs , DnGEBGUs , and DnBAMs ), saccharide biosynthesis ( DnA1E , DnAATPSs , and DnSUS1 ), and saccharide transport ( DnERD6L16 , DnWRPC , and DnPP2A2 ). These findings provide valuable insights into improving saccharide production through molecular breeding and wild like cultivation. They will be beneficial for saccharide based application of Dendrobium nobile in the healthcare and pharmaceutical industry.