Reynoutria japonica Houtt. Transformed Hairy Root Cultures as an Effective Platform for Producing Phenolic Compounds with Strong Bactericidal Properties

Reynoutria japonica Houtt. is the source of various phenolic compounds: phenolic acids, flawan-3-ols, and stilbenes, with a broad range of biological activity. The rhizome (underground organ of these plants) is abundant in secondary metabolites but, in natural conditions, may accumulate various toxic substances (such as heavy metals) from the soil. The principal objective of this research was to produce transformed cultures of R. japonica hairy roots that would serve as a valuable source of phenolic compounds, independent of environmental resources. The transformation was performed using a variety of wild strains of Rhizobium rhizogenes bacteria, of which only strain A4 (ATCC 31798) proved effective. The molecular characterization of transformed clones was performed using PCR. The biometric parameters (growth index and dry weight content), phenolic compounds accumulation (DAD-HPLC), antioxidant capacity (DPPH, CUPRAC), and bactericidal properties against Staphylococcus aureus with various sensitivity to antibiotics were evaluated. Two obtained transformed clones (RJ 9 and 30) exhibited the incorporation of the entire bacterial T-DNA into genomic DNA, while clones RJ 10 and 11 demonstrated only the presence of the LT-DNA sequence. The results demonstrated an increase in flawan-3-ols (catechins) accumulation in hairy root tissue relative to non-transformed (NT) plants. Moreover, hairy roots exhibited enhanced antioxidant activity and bactericidal properties compared with NT roots and NT shoots, respectively.