Identification of molecular mechanisms for functional specialization of the dimorphic chloroplasts in single-cell C4 species

• Applicant: Professor Dr. Sascha Offermann
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2012 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 212429042

The discovery that Kranz anatomy is not required for C4 photosynthesis challenges our view about the structural and molecular requirements of C4 photosynthesis. It has been recently established that singlecell C4 (SCC4) species perform C4 photosynthesis within individual cells by partitioning of the necessary biochemical reactions in two different chloroplast types. This is remarkable since it currently represents the only known case of specialized plastids or even organelles within individual cells in any organism. However, it is completely unknown how chloroplasts can accumulate different sets of proteins and therefore functionally specialize within individual cells. We propose here to identify the molecular mechanism allowing the chloroplasts of SCC4 species to accumulate different nucleus-encoded proteins. We will test, if the chloroplasts either differentially import or degrade proteins or if the mRNA for differentially accumulating proteins are targeted to the respective chloroplast types. Furthermore, we will identify the elements (transit peptides, coding regions or untranslated regions of the corresponding mRNAs) which are necessary and sufficient for differential accumulation. Our studies will not only provide new insights into the molecular mechanisms of SCC4 photosynthesis, but might ultimately enable the specific engineering of separate reaction compartments in the form of specialized chloroplasts into cells. This is for example desirable whenever newly introduced synthetic pathways would otherwise interfere with existing ones if occurring in the same reaction compartment.

• DFG Programme: Research Grants