Controlling mitochondrial and chloroplast volume and distribution through alternative splicing of a CLU family gene in Marchantia polymorpha

• Applicant: Professor Dr. Sven B. Gould
• Subject Area: Plant Cell and Developmental Biology ; Cell Biology
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 581702633

The size of any given cell compartment is no coincidence, but the result of a continuously orchestrated feedback loop. The eukaryotic ancestor grew massively in size during its origin, likely a requirement and consequence of accommodating the bacterial endosymbiont that evolved into the mitochondrion. The size and number of mitochondria across eukaryotes differs significantly, but their overall mass is optimized to serve the physiological requirements of the cell and tissue. The same holds true for the second organelle of endosymbiotic origin that is found in plants and algae, the plastid. Hence, there is a machinery at play that carefully monitors the overall mass of mitochondria and plastids in plant cells, but the molecular details of which remain poorly understood. Maintenance of a functional organelle to cytosol volume ratio of mitochondria and plastids is connected to the genes FRIENDLY and REC, respectively. This proposal plans to explore the single gene of the liverwort Marchantia polymorpha that we termed MpCLU, and for which we have obtained preliminary data that it serves both mitochondrial and plastid organelle volume control through alternative splicing affecting exon 22. Structural predictions suggest that the presence of exon 22 causes an alternative TPR motif configuration located within the C-terminus. Our working hypothesis is that this change in the TPR motif through alternative splicing decides whether the protein variant downstream serves either mitochondrial or plastid biology. This kind of C-terminal TPR motif shift has not yet been reported for neither FRIENDLY or REC proteins. It presents us with a unique feature from which to understand this protein family and the overall mechanism of differential organelle volume control, which is so far lacking from the existing literature on both animals and plants.

• DFG Programme: Research Grants