We compared the biochemical profiles of Physalis ixocarpa hairy roots transformed with Agrobacterium rhizogenes ATCC and A4 strains with non-transformed root cultures. The studied clones of A4- and ATCC-induced hairy roots differed significantly; the latter showed greater growth potential and greater ability to produce secondary metabolites (tropane alkaloids) and to biotransform hydroquinone to arbutin. We compared glucose content, alanine and aspartate aminotransferase activity, and L-phenylalanine ammonia-lyase activity. We analyzed markers of prooxidant/antioxidant homeostasis: catalase, ascorbate peroxidase, oxidase, glutathione peroxidase and transferase activity, and the levels of ascorbate, glutathione, tocopherol and lipid peroxidation. We found that transformation induced strain-specific regulation, including regulation based on redox signals, determining the rate of allocation of carbon and nitrogen resources to secondary metabolism pathways. Our results provide evidence that A. rhizogenes strain-specific modification of primary metabolites contributed to regulation of secondary metabolism and could determine the ability of P. ixocarpa hairy root clones to produce tropane alkaloids and to convert exogenously applied hydroquinone to pharmaceutically valuable arbutin. Of the studied parameters, glucose content, L-phenylalanine ammonia-lyase activity and alanine aminotransferases activity may be indicators of the secondary metabolite-producing potential of different P. ixocarpa hairy root clones.
Recent studies revealed that reactive oxygen species, antioxidants and related redox signals are key elements in the regulation of plant defense responses, including the synthesis of secondary metabolites. In this work the potential of artichoke (Cynara scolymus L.) cell suspensions to produce cynarin was studied in relation to the antioxidant profile of the cultures. There were determined the total antioxidant capacity and concentrations of H₂O₂, ascorbate and total phenolics, as well as activities of ascorbate and guaiacol peroxidases, ascorbate oxidase and catalase at different stages of the culture growth cycle in relation to the production of cynarin. Suspension cultures revealed a growth-linked capacity to produce cynarin as identified by qualitative HPLC analysis. The cynarin accumulation kinetics during the exponential phase of growth correlated with the total antioxidant capacity of water-soluble antioxidants whereas the profiles of total phenols and total antioxidant capacity of water-insoluble antioxidants differed. The lowest ascorbate-related antioxidant capacity coincided with the maximum cynarin accumulation in the early stationary phase. The regulation of growth-related prooxidant/antioxidant balance in the artichoke suspension cultures involved the peroxidase/phenolics/ascorbate system scavenging H₂O₂, further affected by ascorbate- and H₂O₂-metabolizing enzymes. These results may be of interest in biotechnological strategies aimed at optimizing the production of secondary metabolites in plant cultures in vitro.
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