Development of metabolic engineering approaches to regulate the content of total phenolics, antiradical activity and organic acids in callus cultures of the highbush blueberry (Vaccinium corymbosum L.)

Blueberry (Vaccinium corymbosum L.) is increasingly cultivated to produce high quality berries for consumption and potential applications in medicine, nutrition and as industrial precursors. Seasonal availability sets limitations on chemical compound isolation from cultivated plants. Biotechnological solutions, such as tissue cultures and metabolic engineering, can provide sufficient amounts of plant material with reasonably high metabolite levels, which may be adjusted by different strategies. Here, we describe our approach to modifying total phenolic content (TPC), antiradical activity (ARA) and amounts of selected organic acids in in vitro cultures of two varieties of V. corymbosum by varying the growth media. TPC, ARA and acid levels were determined in mature leaves of field-grown plants and in stable callus cultures derived from leaves of varieties ‘Bluecrop’ and ‘Duke’ grown on Murashige-Skoog (MS) and Woody plant (WP) media supplemented with varying concentrations and combinations of different plant growth hormones. TPC varied from 83 mg g dry weight (DW) to 142 mg g DW in leaves of ‘Bluecrop’ and ‘Duke’, respectively, and correlated with their ARA with ‘Duke’ at the lead. For callus cultures the highest ARA, as well as the highest TPC of 94 mg g DW was observed in ‘Bluecrop’ grown on WP medium with 2,4-dichlorophenoxyacetic acid (2,4-D). High level of quinic acid was found in the mature leaves of all tested varieties, while callus cultures exhibited relative increase in amounts of malic, succinic and citric acids instead. Oxalic acid was found only in callus cultures.