Research focus

The research objectives of the Plant Gene Regulation group are to understand and explore mechanisms that govern gene expression in plants. Currently, the research group focuses on translational applications of plant transformation and transgene expression for molecular farming. Our major goal is to further develop the seed platform in order to create an alternative cost effective system for the production of complex recombinant proteins, which are difficult to produce in microbial systems.

Plants are gaining acceptance as a platform for large-scale production of recombinant proteins. The main advantage is the anticipated cost savings, reflecting the large amount of biomass that can be produced in a short time with no need for specialized equipment or expensive media. Seed based platforms are particularly attractive because they allow recombinant proteins to stably accumulate for long periods of time at a relatively high concentration in a compact biomass in which they are protected from degradation.

Our research is focused on the use of non-food dicotyledonous species for the production of recombinant proteins, using Arabidopsis as a model. By using a seed-specific expression cassette based on the regulatory signals of seed storage proteins of common bean (Phaseolus vulgaris), and by targeting the recombinant protein to the endoplasmatic reticulum (ER), we obtained the highest yields of recombinant proteins in plants described so far: a single-chain variable fragment (scFv) accumulated to levels in excess of 36% of total soluble protein (TSP) in homozygous Arabidopsis seeds, while retaining its antigen-binding activity and affinity (De Jaeger et al., 2002). The major advantage of Arabidopsis seeds as production platform for important and high value proteins is the small size of the plant and consequently the small amount of space needed to grow a large amount of plants. Furthermore, Arabidopsis plants can easily grow in greenhouse conditions.

Currently, we aim to investigate the effect of the recombinant protein overexpression in seeds at the molecular and physiological level and determine whether silencing pathways are active in plants. Additionally, a whole range of proteins are produced in the seeds: antibodies against veterinary diseases, antibodies which will be used as functional tool for plant biotechnological research and subunit vaccines. Finally, we want to bridge the gap between  academic research and industrial valorization of the seed-based heterologous protein production platform.

In the past, we developed several approaches to increase the frequency of single-copy transformants by using the site-specific Cre/loxP recombination system (De Buck et al., 2007; Marjanac et al., 2008; De Paepe et al., 2009). Additionally, we showed that post-transcriptional gene silencing was determined by the tissue type, nature of the silencing inducer locus and the differential expression of the targeted gene (Marjanac et al., 2009) and that posttranscriptional silencing spreads along the 35S driven target pre mRNA, is a time dependent gradual process and results in silencing of genes not homologous with the silencing inducing locus (Bleys et al., 2006a; Bleys et al 2006b; Vermeersch et al., 2010). Finally, five missense mutants and one recombination substrate of the ß-glucuronidase (GUS)-encoding gene of Escherichia coli were developed as a tool for detecting mutation and recombination events in transgenic Arabidopsis plants by reactivation of GUS activity in clonal sectors (Vanderauwera et al., 2008).