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“MICROMETABOLITE” – Research Training Network on the Microbial Enhancement of Bioactive Secondary Metabolite Production in Plants

Periodic Reporting for period 1 - MICROMETABOLITE (“MICROMETABOLITE” – Research Training Network on the Microbial Enhancement of Bioactive Secondary Metabolite Production in Plants)

Reporting period: 2017-05-01 to 2019-04-30

Research in MICROMETABOLITE focuses on medicinal plants and their associated microorganisms. We strengthen beneficial plant-microbial interrelations to obtain high qualities of plant-derived secondary metabolites, which are the active ingredients of bio-based pharmaceutics and cosmetics. The MICROMETABOLITE research and training platform puts science into practice and supports long-term partnerships between academia and industry.

Plant-associated microorganisms such as endophytic bacteria and fungi (which reside inside living plants) and soil-borne, mycorrhizal fungi are essential to optimum plant health and growth. They are physiologically tightly interlinked with their hosts, and, hence, may induce or modulate the production of plant secondary metabolites. Microbial activities that enhance plant nutrient uptake may influence major synthesis pathways, in addition to external influences from herbivores, pathogens, and the abiotic environment. Moreover, endophytic bacteria and fungi themselves are known as producers of various plant-derived bioactive compounds.

In MICROMETABOLITE, we extract from the roots of Lithospermum and Alkanna plants belonging to the Boraginaceae family various naphtoquinone derivatives (e.g. alkannin and shikonin, A/S). These compounds have shown positive effects in tissue regeneration and wound healing and have proven antimicrobial, anti-inflammatory, anti-HIV-1, and anti-cancer activities. Boraginaceae-derived compounds are already used in various cosmetics and medicinal products, and there is growing interest in expanding the range of pharmaceutical application. However, synthesis in plant cultivation systems is often inconsistent and gives low yields as compared with wild plants growing at their native sites, which presently limits commercialization.
In the ITN’s first reporting period, we analysed relationships between the plants’ content of A/S or other secondary metabolites, the plant genotype, and the plant-associated microflora. For this, Alkanna tinctoria plants were cultivated in the greenhouse and sampled for analysing A/S contents and the enantiomeric A:S ratio, and for identification of A/S and derivatives. The fruiting stage was found most promising regarding plant A/S production, and it was shown that alkannin derivatives predominated over shikonin in the cultivated A. tinctoria plants.
Regarding the microbial communities associated with A/S producing plants, Burkholderiaceae, Pseudomonadaceae and Xanthobacteriaceae were the most common bacterial taxax while Plectosphaerella, Penicillium, Fusarium and Trichoderma sp. were the most common fungal taxa.

In several isolation campaigns, wild A. tinctoria plants and rhizosphere soil were sampled in Thessaloniki and in Athens. Fungal endophytes were isolated and together with Glomeromycota AMF strains were tested for plant growth promotion and secondary metabolite promotion in Echium vulgare.The biological activity of A/S and derivatives was evaluated, among others, in terms of cytotoxicity and induction/inhibition of adipogenesis, and A/S were used as active compounds in cell-based tissue engineering scaffolds. Furthermore, we started to establish novel in vitro and in vivo propagation systems of Boraginaceae plants and associated them with arbuscular mycorrhizal fungi (AMF) and bacteria.
In the following, we will characterize Boraginaceae secondary metabolites in dependence of the plant genotype, and we will demonstrate how metabolite quantity and quality are influenced by plant-associated microorganisms. Our research will feed into a newly established, innovative plant production system that integrates microorganisms and is operating with a specific protocol. MICROMETABOLITE’s research will be readily implemented by industry, and it will widen the market’s repertoire of Boraginaceae plant-based pharmaceutics and cosmetics.
Lithospermum erythrorhizon (photo: Philipp Rödel, IFP)
Confocal laser scanning microphotograph of GFP-tagged bacteria (photo:Stephane Compant, AIT)