Role of the phloem in the biochemistry and ecophysiology of benzylisoquinoline alkaloid metabolism

Abstract

Benzylisoquinoline alkaloids (BIAs) are a diverse group of biologically active specialized metabolites produced mainly in four plant families. BIA metabolism is likely of monophyletic origin and involves multiple enzymes yielding structurally diverse compounds. Several BIAs possess defensive properties against pathogenic microorganisms and herbivores. Opium poppy (Papaver somniferum: Papaveraceae) has emerged as a model system to investigate the cellular localization of BIA biosynthesis. Although alkaloids accumulate in the laticifer cytoplasm (latex) of opium poppy, corresponding biosynthetic enzymes and gene transcripts are localized to proximal sieve elements and companion cells, respectively. In contrast, BIA metabolism in the non-laticiferous meadow rue (Thalictrum flavum; Ranunculaceae) occurs independent of the phloem. Evidence points toward the adoption of diverse strategies for the biosynthesis and accumulation of alkaloids as defensive compounds. Recruitment of cell types involved in BIA metabolism, both within and external to the phloem, was likely driven by selection pressures unique to different taxa. The biochemistry, cell biology, ecophysiology, and evolution of BIA metabolism are considered in this context.

Tissue‐specific metabolite profiling of benzylisoquinoline alkaloids in the root of Macleaya cordata by combining laser microdissection with ultra‐high‐performance liquid chromatography/tandem mass spectrometry

“…By comparing the MS and MS 2 data and the proposed fragmentation pathways (Supplementary Figs. S15 and S16) with those reported in the literature, [31,34,35,[42][43][44][45] compounds 25,29,31,33,34,36,37,38,39,40,41,44,45,48 and 49 were identified as 7,8-didemethylchelerythrine, 7-O-demethylchelerythrine, SG, CHE, chelirubine(CHEb), chelilutine(CHEt), macarpine (MAC), oxysanguinaine, oxychelerythrine, bocconoline, norchelerythrine, dihydrochelerythrine, norsanguinarine, 10methoxylnorchelerythrine and dihydrosanguinarine, respectively.…”

“…5(b)), and these compounds were hydrophobic and specifically distributed in the outermost part of roots, which was consistent with protection against pathogens, herbivores, and environmental stresses. [46][47][48] XVB contained more alkaloids probably because of their function of transporting secondary metabolites. [49,50] The tissue-specific distribution was further confirmed using UHPLC/QqQMS by the quantitative analysis of the six main bioactive components, including PRO, ALL, SG, CHE, DHCHE and DHSG in M. cordata.…”

Plant Chemical Defenses: Are all Constitutive Antimicrobial Metabolites Phytoanticipins?

“…Due to their various pharmacological properties, alkaloids have been exploited for centuries for human benefits [31,59]. Nonetheless, in many circumstances the ecological roles of alkaloids remain unknown, with exceptions that include the benzylisoquinoline [60] and pyrrolizidine alkaloids [61]. Chosen here as representative examples of each group, the benzylisoquinolines, sanguinarine and chelerythrine, have been reported to display antibacterial and antifungal activity against important plant pathogens, while hunnemanine inhibited spore germination [60].…”

Cell-specific localization of alkaloids in Catharanthus roseus stem tissue measured with Imaging MS and Single-cell MS

“…Moreover, proteome analysis of opium poppy shows that enzymes for morphine biosynthesis are localized either in sieve elements or LCs (15)(16)(17). These results suggest that the metabolic intermediates in morphine biosynthesis are likely to be shuttled between the two cell types of sieve elements and LCs, and that LCs are metabolically active (16).…”