Max Planck Institute of Molecular Plant Physiology
Organelle Biology and Biotechnology
The overarching goal of the research in the group is to obtain a systems-level understanding of chloroplast and mitochondrial function in the context of the genetic and metabolic networks operating in plant cells. We explore diverse aspects of organelle biology, ranging from the systematic analysis of gene expression and its regulation at all levels (transcription, RNA metabolism, translation, protein stability, and protein complex assembly) to fundamental questions of genome stability, inheritance and evolution. We develop tools and technologies for organellar genome engineering, and apply them to facilitate new applications in biotechnology and synthetic biology. In addition, we study the genetics and epigenetics of two algal models: the green alga Chlamydomonas reinhardtii and the red alga Porphyridium purpureum.
Research in the group currently focuses on four main areas that are highly interconnected:
1. Organelle biology
We study the mechanisms and regulation of plastid gene expression at all levels, the co-ordination of organellar gene expression with the expression of the nuclear genome, the biogenesis of the organelles and their energy-transducing membrane systems (in photosynthesis and respiration), the mechanisms of organelle inheritance, and the evolution of organellar genomes.
Discovery of environmental and genetic factors that influence the inheritance of the chloroplast genome. The chloroplast genome is inherited maternally under standard growth conditions (left), as evidenced by the lack of pollen transmission of an antibiotic resistance gene in tobacco. Knock-out of a genome-degrading nuclease (dpd1 mutant) or mild chilling stress (10°C) result in low-level biparental inheritance, whereas combination of the environmental factor and the genetic factor (dpd1, 10°C; right) leads to strong biparental inheritance.
Discovery of environmental and genetic factors that influence the inheritance of the chloroplast genome. The chloroplast genome is inherited maternally under standard growth conditions (left), as evidenced by the lack of pollen transmission of an antibiotic resistance gene in tobacco. Knock-out of a genome-degrading nuclease (dpd1 mutant) or mild chilling stress (10°C) result in low-level biparental inheritance, whereas combination of the environmental factor and the genetic factor (dpd1, 10°C; right) leads to strong biparental inheritance.
We have a long-standing interest in developing tools and technologies for genetic engineering of the plastid, mitochondrial and nuclear genomes of model plants, crops and algae. Recently developed technologies include (i) chloroplast transformation protocols for several model species and crops, (ii) genome editing methods for mitochondrial genomes, (iii) engineered green algal strains that facilitate high-level nuclear transgene expression, and (iv) efficient expression technologies for red algae based on nuclear plasmids.
Development of chloroplast transformation technology for the model plant Arabidopsis thaliana. Plastid-transformed cell lines are selected from microcalli bombarded with DNA-coated gold particles.
Development of chloroplast transformation technology for the model plant Arabidopsis thaliana. Plastid-transformed cell lines are selected from microcalli bombarded with DNA-coated gold particles.
Chloroplast genome engineering (plastid transformation) offers a number of unique attractions, including high-level foreign protein accumulation, convenient transgene stacking in synthetic operons and increased transgene containment due to maternal chloroplast inheritance. We are using the tools and technologies we develop for plastid genome engineering to facilitate new applications in biotechnology and synthetic biology. We are currently pursuing various applications in metabolic pathway engineering, molecular farming and resistance engineering, and we are also designing and booting up synthetic organellar genomes.
Engineering of the metabolic pathway for astaxanthin biosynthesis into the chloroplast genome of tobacco plants. The orange pigment astaxanthin is in large and growing demand, driven by its powerful antioxidant properties and its increasing use in dietary supplements, functional foods, cosmetics, and aquaculture (where it is required to achieve the pink-red hue in farmed salmon). Tapping the carotenoid biosynthetic pathway inside chloroplasts, large amounts of astaxanthin can be synthesized by expressing the pathway enzymes from the plastid genome.
Engineering of the metabolic pathway for astaxanthin biosynthesis into the chloroplast genome of tobacco plants. The orange pigment astaxanthin is in large and growing demand, driven by its powerful antioxidant properties and its increasing use in dietary supplements, functional foods, cosmetics, and aquaculture (where it is required to achieve the pink-red hue in farmed salmon). Tapping the carotenoid biosynthetic pathway inside chloroplasts, large amounts of astaxanthin can be synthesized by expressing the pathway enzymes from the plastid genome.
The goals of our research program in experimental evolution are to develop experimental systems that allow us to observe major processes in genome evolution in real time, including endosymbiotic gene transfer (gene transfer from the chloroplast and mitochondrial genomes to the nuclear genome), and horizontal gene and genome transfer. We use these experimental systems to study the molecular mechanisms underlying gene transfer and genome evolution, and we apply them to create new opportunities in plant breeding, biotechnology and synthetic biology.
Example of a novel species generated by horizontal genome transfer. The new species arose from grafting hygromycin-resistant cigarette tobacco (Nicotiana tabacum, a herbaceous species with 48 chromosomes) with kanamycin-resistant tree tobacco (Nicotiana glauca, a woody species with 24 chromosomes). After establishment of the graft union, the graft site was excised and subjected to double selection for kanamycin and hygromycin. Regenerating doubly resistant plants have 72 chromosomes, which is the sum of the chromosome numbers of their two progenitor species. The new synthetic allopolyploid species, dubbed Nicotiana tabauca, outgrows its progenitor species and shows many traits that are intermediate between those of its two progenitor species (modified after Fuentes et al., Nature 2014).
Example of a novel species generated by horizontal genome transfer. The new species arose from grafting hygromycin-resistant cigarette tobacco (Nicotiana tabacum, a herbaceous species with 48 chromosomes) with kanamycin-resistant tree tobacco (Nicotiana glauca, a woody species with 24 chromosomes). After establishment of the graft union, the graft site was excised and subjected to double selection for kanamycin and hygromycin. Regenerating doubly resistant plants have 72 chromosomes, which is the sum of the chromosome numbers of their two progenitor species. The new synthetic allopolyploid species, dubbed Nicotiana tabauca, outgrows its progenitor species and shows many traits that are intermediate between those of its two progenitor species (modified after Fuentes et al., Nature 2014).
