Genetic transformation of plant cells as a possible strategy for the production of bioactive compounds or biopolymers

Biotechnologies are currently applied to a wide range of fields, which span from the production of active compounds for human health to high-tech materials used in industry. Among biotechnologies, genetic engineering can modify gene content and/or expression in different organisms such as bacteria, yeasts, animal cells, and plants. Recently, plant genetic engineering has been mainly focused on conferring beneficial agronomic properties to crops, such as pest or disease resistance, stress tolerance, or improved yield. Here we report on examples of biotechnologies employed for the production of high-added value compounds from plants, which might serve as "green" bioreactors. Two research lines are currently carried out at the Botanical Garden laboratories of Urbino University, with the support of various external collaborations. The first one aims at inducing the production of anthocyanins, secondary metabolites with marked nutraceutical properties, in apple pulp calli. To reach this goal, apple calli has been transformed via Agrobacterium tumefaciens vector with a gene cassette harbouring Sn, a maize helix-loop-helix (bHLH) transcription factor and a marker for kanamycin resistance. Ectopically expression of Sn gene can boost the accumulation of anthocyanins in different species and under different environmental conditions. Here we show that the expression of this gene is sufficient to significantly promote the synthesis and accumulation of anthocyanins in apple calli exposed to light compared to control calli transformed with the Gus reporter gene. The second research line uses genetic engineering to modify the major reserve protein accumulated in Phaseolus vulgaris (common bean) seeds, called phaseolin, to produce an environmentally friendly biopolymer. Our idea starts from previous studies that demonstrated the possibility of forming disulfide bridges by a genetically modified version of phaseolin with a single cysteine residue insertion in the cterminal tail. We thought that expressing this protein in a closed compartment such as Nicotiana tabacum chloroplasts facilitated the formation and accumulation of polymerized forms of phaseolin. In this study, the biochemical basis underlying the synthesis, accumulation and purification of polymeric forms based on mutated-phaseolin in the chloroplast of transgenic tobacco plants is described.