High-resolution MALDI mass spectrometry imaging of gallotannins and monoterpene glucosides in the root of Paeonia lactiflora

Abstract

High-resolution atmospheric-pressure scanning microprobe matrix-assisted laser desorption/ionization mass spectrometry imaging (AP-SMALDI MSI) at 10 μm pixel size was performed to unravel the spatio-chemical distribution of major secondary metabolites in the root of Paeonia lactiflora. The spatial distributions of two major classes of bioactive components, gallotannins and monoterpene glucosides, were investigated and visualized at the cellular level in tissue sections of P. lactiflora roots. Accordingly, other primary and secondary metabolites were imaged, including amino acids, carbohydrates, lipids and monoterpenes, indicating the capability of untargeted localization of metabolites by using high-resolution MSI platform. The employed AP-SMALDI MSI system provides significant technological advancement in the visualization of individual molecular species at the cellular level. In contrast to previous histochemical studies of tannins using unspecific staining reagents, individual gallotannin species were accurately localized and unequivocally discriminated from other phenolic components in the root tissues. High-quality ion images were obtained, providing significant clues for understanding the biosynthetic pathway of gallotannins and monoterpene glucosides and possibly helping to decipher the role of tannins in xylem cells differentiation and in the defence mechanisms of plants, as well as to investigate the interrelationship between tannins and lignins.

Comparative transcriptomics characterized the distinct biosynthetic abilities of terpenoid and paeoniflorin biosynthesis in herbaceous peony strains

“…The list included several KEGG terms of secondary metabolite biosynthesis, such as: Terpenoid backbone biosynthesis (P-value < 0.0152), Glycerophospholipid metabolism (P-value < 0.0001), Inositol phosphate metabolism (P-value < 0.0001), Pyruvate metabolism (P-value < 0.0002), Seleno compound metabolism (P-value < 0.0298), Ascorbate and aldarate metabolism (P-value < 0.0172) and Butanoate metabolism (P-value < 0.0352). P. lactiflora are generally known to have abundant secondary metabolites (Li et al, 2016a;Liu et al, 2017;Ma et al, 2016). Our transcriptome and pathway enrichment results are consistent with the metabolism profiling studies.…”

Peer Review #2 of "Comparative transcriptomics characterized the distinct biosynthetic abilities of terpenoid and paeoniflorin biosynthesis in herbaceous peony strains (v0.1)"

“…P. lactiflora are generally known to have abundant secondary metabolites (Li et al 2016a;Liu et al 2017;Ma et al 2016). Our transcriptome and pathway enrichment results are consistent with the metabolism profiling studies.…”

Exodermis and endodermis are the sites of xanthone biosynthesis in Hypericum perforatum roots

“…In secondarily thickened roots of Panax species ( P. ginseng , P. quinquefolius , and P. notoginseng ), ginsenosides were primarily localized to the cork (Wang et al ., ). In roots of Paeonia lactiflora , gallotannins accumulated in the cork and in xylem regions (Li et al ., ). All these studies thus correlated the presence of defence compounds with outer tissues.…”