Integrative Metabolome and Transcriptome Analyses Reveal the Effects of Plucking Flower on Polysaccharide Accumulation in the Rhizomes of Polygonatum cyrtonema Hua

Polysaccharides are the major bioactive components of Polygonatum cyrtonema Hua, and their biosynthesis and accumulation are influenced by many agronomic practices. In this study, we applied integrative metabolome and transcriptome analyses to investigate the accumulation of bioactive components in one-year-old (1Y) and six-year-old (6Y) rhizomes of P. cyrtonema Hua treated with a plucking flower. The compound content analysis suggested that six-year-old treated rhizomes (T6) accumulated the highest polysaccharide content compared to that of one-year-old treated rhizomes (T1), one-year-old untreated rhizomes (C1), and six-year-old untreated rhizomes (C6). Metabolomics analysis showed that 4-O-galactopyranosylxylose, 6-O-alpha-l-arabinopyranosyl-d-glucopyranose, d-arabinose and dl-xylose significantly accumulated in T6 rhizomes. Carbohydrate metabolic pathways, including "glycolysis/gluconeogenesis", "pentose and glucoronate interconversions" and "amino sugar and nucleotide sugar metabolism" were highly correlated with polysaccharide biosynthesis and accumulation. The transcriptome data indicated that UPG2, GPI, and GALE were positively upregulated in T6_vs_C6. In parallel, RHM and PEI were down-regulated in T6_vs_C6. Taken together, this study not only indicates that the candidate metabolites/metabolic pathways and genes affected by plucking flowers may influence the accumulation of polysaccharides in the rhizomes but also provides an easy and feasible agronomic practice to facilitate the accumulation of polysaccharides in the rhizomes of P. cyrtonema Hua.