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The metal ions iron (Fe) and copper (Cu) are essential to all living organisms; for instance respiratory and photosynthetic electron transfer chains depend on these metal cofactors. We investigate how plants regulate the incorporation of Fe and Cu ions into proteins that function in photosynthesis in plant chloroplasts. Despite being essential, these metal ions can also be toxic when present in excess, and all organisms need to regulate uptake and distribution. This homeostatic control is especially complex in plants because these sessile organisms must do with the ions present in the local soil; different distributions of metal ions are needed during the vegetative growth phase and seed development; the presence of plastids gives plants a more complex sub-cellular organization compared to other eukaryotes. To study the machinery involved in metal cofactor homeostasis in plant chloroplasts, we are analyzing Arabidopsis thaliana genes that encode plastid-localized proteins involved in metal homeostasis. We use both a genetic approach (point mutants and knock-out mutants, over-expression, and RNAi), and a biochemical approach (experiments with isolated proteins and chloroplasts, immuno-localization experiments) to elucidate the mechanisms involved. A thorough understanding of metal ion homeostasis may benefit crop productivity, human nutrition and renewable biofuel production. The photosynthetic activity of chloroplasts is pivotal to plant dry mass production. Furthermore, an important determinant of the nutritional value of plants is their metal content, particularly the iron content of edible parts.
In the Pilon-Smits lab, we do multidisciplinary research that ranges from cells to whole plants to ecosystems. An important common denominator is selenium (Se): an essential element with anticarcinogenic and antiviral properties, but also a toxin and environmental pollutant. We study plant Se tolerance and accumulation using genetic/genomic tools and biotechnology and biochemistry. At the same time, we are very interested in ecological and evolutionary aspects of Se hyperaccumulation: the capacity of certain species to accumulate Se up to 1% of dry weight. Our findings indicate that Se hyperaccumulation has evolved as a protection from biotic stresses. A better understanding of plant Se metabolism and hyperaccumulation may ultimately lead to the development of pathogen- and pest-resistant, anticarcinogenic, Se-fortified crops, and plants with superior properties for the phytoremediation of Se-polluted soils and waters. A relatively recent interest in our lab is the use of hemp for selenium phytoremediation and biofortification.