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Regulation of iron-sulfur (Fe-S) cluster assembly in plastids and coordination with plant physiology

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Formation of iron-sulphur clusters in plants

Photosynthesis, the ability to convert solar energy into food, is critical for maintaining all life forms on earth. The versatile cofactors — iron-sulphur (Fe-S) clusters are key components of chloroplasts and play a major role in photosynthesis.

Climate Change and Environment

In the context of global climate change and dynamic environmental conditions, understanding regulation and function of Fe-S clusters in the chloroplast is critical. With this in mind, researchers initiated the EU-funded project INTEGRREGULFESPLAST. Previous research has shown that the cysteine desulphurase enzyme, CpNifS is required for S supply during Fe-S cluster assembly in chloroplasts. The protein CpSufE binds to CpNifS to assemble Fe-S clusters. However, knowledge about how exactly chloroplasts assemble these clusters is still limited. To resolve this, researchers applied an integrated biochemical-physiological-genetic approach in the model plant Arabidopsis thaliana to study the chloroplast Fe-S assembly system. Plants were grown in hydroponic conditions to assess their response to variations in nutrition and environment. In particular, differing Fe and S levels as well as varied lighting conditions were tested. Researchers assessed changes in physiological and phenotypic parameters such as plant biomass, chlorophyll content, photosynthetic activity and gene expression. Using techniques such as Western-blotting and antibody collection, the scientists observed changes in target protein levels and Fe-S regulation. Inducible artificial RNA interference constructs were designed and selected KO plant mutants were used to conditionally suppress proteins and study their functions. Project members already isolated several components belonging to certain protein families associated with Fe-S biogenesis in the chloroplast using sequence analogy. An important discovery was the interaction of the protein adenosine 5′-phosphosulphate reductase (APR) with SufE and its role in S metabolism during Fe-S cluster formation. Results revealed a depleted supply of APR proteins when Fe supply is low suggesting that cysteine desulphurase activity is Fe-dependent. However, NifS and SufE levels were unaffected by Fe levels. INTEGRREGULFESPLAST has linked protein function with whole plant physiology. Novel insight has been gained into the early regulatory processes involved in Fe-S biogenesis. Project activities could ultimately be applied to enhance biomass production and agricultural productivity with important implications for global food security.

Keywords

Fe-S cluster, photosynthesis, chloroplast, cysteine desulphurase enzyme, CpNifS, CpSufE, hydroponic, physiological, phenotypic, Western blotting, antibody, protein, RNA interference construct, APR, food security

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