Plant Biotechnology and Metabolic Engineering
Prof. Dr. Heribert Warzecha
Whether suffering an attack, luring pollinators, or basking in symbiotic comfort, plants constantly participate in molecular interplay with their environment. Stealthily sequestering dangerous poisons, freely exuding volatile attractants, or tirelessly sending and responding to various cues, they are versatile chemists producing myriad specialized compounds. Secondary metabolites thus come into view as the means of inter-organismal and intra-environmental communication in this dynamic continuum.
The biosynthetic capacity of plants is founded upon an intricate matrix of metabolic trails and rooted in a near inexhaustible supply of photosynthetic energy. It comes as little surprise then, that plants and plant-derived preparations have been used as commodities and remedies since time immemorial, and that the application of plant natural products (PNPs) in the development of new drugs and drug leads is still alive and well today.
Modulation of plant secondary metabolism: METABOLIC ENGINEERING
For any attempt at targeted engineering of biosynthetic routes leading to specialized compounds of therapeutic and/or economic value, it is of utmost importance to understand the biogenesis of PNPs from ubiquitous primary metabolites. Along with tremendous success in elucidation of several plant metabolic trails, their re-establishment in heterologous hosts has been a hallmark of recent endeavors in the field. However, current metabolic engineering efforts are, in the main, aimed at grafting the pathways to fermentable recipient organisms, like bacteria or yeast. Conducive to activity requirements of many catalytic proteins involved in the build-up of the complex carbon skeletons of interest, especially the latter has proved malleable enough to accommodate plant secondary metabolite production. Still, mere integration of biosynthetic genes into the eukaryote is not a sufficient driver for effective heterologous generation of PNPs in yeast as the issue of precursor supply necessitates substantive pathway engineering and, more often than not, retrieval rates of target compounds remain low, especially relative to their plant-produced counterparts. Conversely, while harboring orthologous metabolic routes, select plant species now emerge as viable vehicles for mobilization and engineering of complex biosynthetic pathways and manufacture of considerable amounts of high-value PNPs.
Drawing on the unique compartmentation of plant cells and capitalizing on the versatility of heterologous plant systems, our research team strives to re-wire them to generate new functionalities within the impressive repertoire of specialized metabolites. In concert with fundamental research aimed at ultimate deciphering of native biosynthetic pathways, we explore novel, combinatorial approaches affording production of new-to-nature, bespoke chemicals of potential commercial value.
Our investigative and engineering efforts focus on the biosynthetic networks yielding monoterpenoid indole alkaloids characteristic of the Indian snakeroot (Rauvolfia serpentina), phenolic secoiridoids indigenous to olive (Olea europaea), and cannabinoids, products of the secondary metabolism of Cannabis sp.
Staniek A., Bouwmeester H., Fraser P.D., Kayser O., Martens S., Tissier A., van der Krol S., Wessjohann L., Warzecha H. 2013. Natural products – modifying metabolite pathways in plants. Biotechnol. J. 8: 1159–1171, doi: 10.1002/biot.201300224.
Staniek A., Bouwmeester H., Fraser P.D., Kayser O., Martens S., Tissier A., van der Krol S., Wessjohann L., Warzecha H. 2014. Natural products – learning chemistry from plants. Biotechnol. J. 9: 326–336, doi: 10.1002/biot.201300059.
Geissler M., Burghard M., Volk J., Staniek A., Warzecha H. 2015. A novel cinnamyl alcohol dehydrogenase (CAD)-like reductase contributes to the structural diversity of monoterpenoid indole alkaloids in Rauvolfia. Planta 243: 813–824, doi: 10.1007/s00425-015-2446-6.
Fräbel S., Krischke M., Staniek A., Warzecha H. 2016. Recombinant flavin-dependent halogenases are functional in tobacco chloroplasts without co-expression of flavin reductase genes. Biotechnol. J., 11: 1586–1594, doi: 10.1002/biot.201600337.
Fräbel S., Wagner B., Kirschke M., Schmidts V., Thiele C.M., Staniek A., Warzecha H. 2018. Engineering of new-to-nature halogenated indigo precursors in plants. Metab. Eng., 46: 20–27, doi: 10.1016/j.ymben.2018.02.003.
Geissler M., Volk J., Stehle F., Kayser O., Warzecha H. 2018. Subcellular localization defines modification and production of Δ9-tetrahydrocannabinolic acid synthase in transiently transformed Nicotiana benthamiana. Biotechnol. Lett. 40: 981–987, doi: 10.1007/s10529-018-2545-0.
We are also involved in a new interdisciplinary project dedicated to sustainable bioproduction of pheromones for insect pest control in agriculture, Susphire: http://susphire.info/susphireproject/
Not just small molecules: CHLOROPLASTS AS HUBS OF THERAPEUTIC PROTEIN PRODUCTION
Plastids, as relicts of endosymbiotic cyanobacteria, feature assorted prokaryotic traits. Chief among them are the efficiently functioning homologous recombination system and polycistronic organization of operons. Further, plant cells harbor a multitude of plastids, chiefly chloroplasts; these, in turn, carry multiple genome reprints. The enumerated characteristics thus set the stage for targeted and highly effective plastid genome manipulation.
In our efforts to harness their tremendous engineering potential, we view plastids as a coordinated system of mini-bioreactors within the larger context of a plant – a biofactory of therapeutically relevant recombinant peptides and proteins.
Our research is grounded upon and inspired by the fundamental principles of synthetic biology, echoing the famous quote of the theoretical physicist Richard Feynman “What I cannot create, I do not understand”.
The main feature of our ‘synthetic biology toolbox’ is the GoldenBraid modular cloning system: https://gbcloning.upv.es/
Vafaee Y., Staniek A., Mancheño-Solano M., Warzecha H. 2014. A modular cloning toolbox for the generation of chloroplast transformation vectors. PLoS ONE 9: e110222, doi: 10.1371/journal.pone.0110222.
Patron, N.J., Orzaez, D., Marillonnet, S., Warzecha, H., Matthewman, C. et al. 2015. Standards for plant synthetic biology: a common syntax for exchange of DNA parts. New Phytol. 208: 13–19, doi: 10.1111/nph.13532.