Mahonia is an important medicinal plant used for the treatment of human diseases. To explore the molecular mechanisms underlying the different pharmacological functions of Mahonia, organ-specific proteomics was performed. Protein profiles of leaves, stems, and roots from 2-year-old Mahonia plants were determined using gel-free/label-free proteomic technique, and totals of 304, 314, and 182 proteins were identified, respectively, and included 36 common proteins. In leaves, the most abundant proteins related to photosynthesis. Furthermore, polyethylene glycol fractionation was used to identify low-abundance proteins in leaves. With this approach, oxidative pentose phosphate-related proteins were identified in leaves. In stems, the main functional categories of proteins were protein synthesis and redox ascorbate/glutathione metabolism. In roots, proteins were mainly related to protein synthesis, stress, and amino acid metabolism. Of the proteins identified, the abundance of calreticulin was markedly higher in roots than that detected in stems and leaves. Many roots-specific proteins, including S-adenosylmethionine synthetase and (S)-tetrahydroprotoberberine oxidase, involved in the biosynthesis of alkaloids, were identified. Consistent with this finding, levels of the alkaloids, which were columbamine, jatrorrhizine, palmatine, tetrandrine, and berberine, were markedly higher in roots compared to those detected in stems and leaves. Taken together, these results suggest that alkaloid biosynthesis is an important function in Mahonia roots.
Keywords: Mahonia; alkaloid; gel-free/label-free proteomics; organ; polyethylene glycol fractionation.