Transcriptome and Metabolome Revealed Highly Required HSPs and Complex Molecules Regulation in Heat-induced Dendrobium officinale (Orchidaceae).

Dendrobium officinale (D. officinale), a precious and rare medicinal herb, is highly vulnerable to heat stress, but its underlying heat-induced molecular mechanism remains elusive. The present project analyzed activities of 4 antioxidant enzymes, and determined the transcriptome and metabolome in heat-induced D. officinale seedings, respectively. The findings indicated that four enzyme activities significantly increased, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD). The transcriptome data revealed 3287 differentially expressed genes (DEGs), of which 1608 DEGs upregulated and 1679 DEGs downregulated. Particularly, heat shock protein family genes (HSPs) were distinctively up-regulated (such as HSP20 gene up-regulated by 7754-fold). Nontargeted metabolome analysis detected a total of 1019 metabolites including 15 significantly different expressed metabolites (DEMs) mainly associated with energy mechanism and antioxidation etc.; Weighted gene co-expression network analysis (WGCNA) of DEGs and DEMs indicated rapidly accumulated HSPs, accelerated energy metabolism and DNA repair etc. The reprogramming of hundreds of genes or metabolites suggested, plant cells adopted highly complex molecular regulation strategies to precisely modulate cell homeostasis, enhance thermotolerance and thermos-morphogenesis in heat-induced D. officinale. The present study provided valuable insights into understanding the molecular regulation and metabolism mechanism in heat-induced D.officinale, which helped advance the genetic breeding for heat-resilient Orchidaceae plants in the future.