Targeted Metabolomics Provide Chemotaxonomic Insights of , with Coupled Transcriptomics Elucidating the Mechanism Underlying Floral Coloration.

, a wild legume forage widely distributed in the Eurasian steppe, demonstrates high genetic and phenotypic variation. with a purely yellow flower (YFM), differing from the general phenotype of with a purple flower (PFM), was recently discovered. The similar characteristics of YFM with have led to conflicting opinions on its taxonomy using traditional morphological methods. The lack of chemotaxonomy information about species and the unclear flower coloration mechanisms have hampered their study. Here, we investigated using targeted metabolomics based on the chemotaxonomy method and elaborated the floral coloration mechanisms using transcriptomics. The identified flavonoids were the same types, but there were different contents in YFM and PFM, especially the contents of cyanidin-3-O-glucoside (C3G), an anthocyanin that causes the purple-reddish color of flowers. The over-accumulation of C3G in PFM was 1,770 times more than YFM. Nineteen anthocyanin-related genes were downregulated in YFM compared with their expression in PFM. Thus, YFM could be defined as a variety of rather than a different species. The loss of purple flower coloration in YFM was attributed to the downregulation of these genes, resulting in reduced C3G accumulation. The taxonomic characteristics and molecular and physiological characteristics of this species will contribute to further research on other species with similar external morphologies.