Figure 5. Combination of natural variations and spatial metabolomics to reveal key metabolite markers associated with important pharmaceutical properties.
In plants, specialized metabolites are often correlated with pigmentation as an evolutionary result (Gaurav and Stacey, 2018; Wang et al., 2018). In most cases, color thought to be associated with three classes of metabolites: flavonoids, carotenoids and betalains (Becker et al. 2011). However, in this study, we found that polyacetylenes are the major contributor of the pigmentation and highly accumulated in red SCs of AR. It has been shown that polyacetylenes are bioactive defensive compounds with anti-cancer and anti-inflammatory activity (Jun et al., 2018; Zhang et al., 2021). Traditionally, cinnabar-like red secretory cavities presented in rhizome cross sections of AR were calledZhushadian in Chinese, one of the most important criteria for the traditional quality assessment of Cangzhu . It is also a typical phenotype of Daodi herbs of Cangzhu , according to the theory “Optimal shape and High quality” proposed by Luqi Huang (Wang et al., 2019; Yuan and Huang, 2020). In this study, we have used modern technology to reveal the relationship of optimal shape (cinnabar-like red secretory cavities), high quality (concentration of characterized polyacetylenes) and possible therapeutic effects of Daodi herbs of Cangzhu , which provide insights into the biological mechanisms of geo-herbalism of TCM.
Multi-omics data from specialized storing structures enables identification of new biosynthetic enzymes involved in pathways of interest (Eljounaidi and Lichman, 2020). For example, comparative proteomic analysis of trichomes, leaves and trichome-depleted leaves in Nepeta mussinii has led to the discovery of the unusual nepetalactol-related short-chain dehydrogenase enzymes (NEPS), which are enriched in the trichome and involved in the biosynthesis of volatile nepetalactones (Lichman et al., 2019). So far, the genome of A. lancea has not been reported and biosynthesis of the red colour determined polyacetylenes still remains elusive. Demonstration of the formation mechanism for coloured SCs thus are challenging. Nevertheless, our results have provided a broad view of chemical distribution of the major compounds of SCs in the herb plant A. lancea and demonstrated that combination of spatial metabolomics with natural variations could be a powerful strategy in revealing chemical markers in non-model plants (Figure 5). It will further pave the way for elucidation of biosynthetic pathways of polyacetylenes in plants, for which most of the catalyzing steps are unknown.