Exodermis and endodermis are the sites of xanthone biosynthesis in Hypericum perforatum roots

Abstract

Xanthones are specialized metabolites with antimicrobial properties, which accumulate in roots of Hypericum perforatum. This medicinal plant provides widely taken remedies for depressive episodes and skin disorders. Owing to the array of pharmacological activities, xanthone derivatives attract attention for drug design. Little is known about the sites of biosynthesis and accumulation of xanthones in roots. Xanthone biosynthesis is localized at the transcript, protein, and product levels using in situ mRNA hybridization, indirect immunofluorescence detection, and high lateral and mass resolution mass spectrometry imaging (AP-SMALDI-FT-Orbitrap MSI), respectively. The carbon skeleton of xanthones is formed by benzophenone synthase (BPS), for which a cDNA was cloned from root cultures of H. perforatum var. angustifolium. Both the BPS protein and the BPS transcripts are localized to the exodermis and the endodermis of roots. The xanthone compounds as the BPS products are detected in the same tissues. The exodermis and the endodermis, which are the outermost and innermost cell layers of the root cortex, respectively, are not only highly specialized barriers for controlling the passage of water and solutes but also preformed lines of defence against soilborne pathogens and predators.

Structure Elucidation of the Main Tetrahydroxyxanthones of Hypericum Seeds and Investigations into the Testa Structure

“…Recent biochemical studies have shown that the exodermis and endodermis of H . perforatum roots are sites of xanthone synthesis . As known for exodermis and endodermis, the testa of a seed is not only a mechanical protective barrier, but also provides protection against microbial degradation.…”

“…The different bioactivities of THX, in particular their antimicrobial and antioxidant properties, could make them interesting as bioactive ingredients for phytomedicinal, pharmaceutical or cosmetic applications. However, further investigations are needed to broaden our knowledge on their biological functions and to explore potential applications.…”

Extracts From Hypericum hircinum subsp. majus Exert Antifungal Activity Against a Panel of Sensitive and Drug-Resistant Clinical Strains.

“…The mechanisms of action of phenols against Candida have been intensively studied and include inactivation of enzyme production ( Evensen and Braun, 2009 ) and anti-biofilm effects ( Evensen and Braun, 2009 ; Shahzad et al, 2014 ). Species belonging to the Hypericum genus are able to synthesize a broad array of such bioactive phenolic compounds, mainly as products of the polyketide metabolism ( Tocci et al, 2018b ), and therefore might contain novel antifungal remedies.…”

Sequential regiospecific gem‐diprenylation of tetrahydroxyxanthone by prenyltransferases from Hypericum sp.

“…Values obtained from untreated cell cultures served as controls. Hypericum actin and histone were reference genes to determine normalized expression (El‐Awaad et al ., ; Tocci et al ., ), using the following equations: …”