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.