Abstract: In order to investigate the regulatory function of thePolygonatum cyrtonemabHLH transcription factor (PcbHLH) in the polysaccharide biosynthesis pathway, transcriptome sequencing was performed for the rhizome, root, leaf, and flower tissues ofP. cyrtonema. Based on transcriptome analysis, 235 PcbHLH transcription factors were identified. Phylogenetic trees were then constructed using their protein sequences and those ofArabidopsis thalianabHLH proteins, dividing the 235 PcbHLHs into 25 subfamilies. 15 PcbHLHs were related to the polysaccharide biosynthesis pathways using KEGG pathway analysis, and subcellular localization analysis indicated that 13 PcbHLHs of which were likely located in the nucleus. Sequence analysis demonstrated that α-helices and random coils were the primary components of their secondary structures. There were two helix-loop-helix (HLH) motifs in their spatial structures. Gene expression profile showed that 9 out of 15 PcbHLHs exhibited the highest expression levels in rhizomes. The study on protein-protein interaction demonstrated that PcbHLHs showed significant interactions with five key enzymes in the polysaccharide biosynthesis pathway, suggesting that PcbHLHs might regulate polysaccharide biosynthesis though these enzymes. This research will provide a theoretical foundation for further exploration for the structure and function of PcbHLHs, and establish an experimental basis for revealing the mechanisms of the polysaccharide biosynthesis pathway regulated by PcbHLH inP. cyrtonema.

Key words: Polygonatum cyrtonema, transcription factor, bHLH, transcriptome analysis, polysaccharide biosynthesis