Submitted by Yangnan Gu on
Mitochondria are double membrane-bound organelles of endosymbiotic origin, descended from α-proteobacteria, and are ubiquitous in eukaryotic cells. They contain their own genome (mtDNA) and play a central role in cellular bioenergetics by generating ATP through oxidative phosphorylation. Mitochondrial dynamics, characterized by frequent fission and fusion events, facilitate the exchange of mtDNA and proteins. This is particularly important in plant cells, where mitochondrial genomes consist of multiple, nonstoichiometric subgenomes, and individual mitochondria often contain incomplete genome sets. Despite its significance, the mechanism of mitochondrial fusion remains poorly understood in any system.
We characterized a novel transmembrane protein in Arabidopsis thaliana, Plant Mitochondria Fusion 1 (PMF1), which localizes specifically to the outer mitochondrial membrane and functions as a positive regulator of mitochondrial fusion. Overexpression of PMF1 dramatically increases mitochondrial size and circularity, leading to the formation of anomalously large fusion-derived structures. Conversely, pmf1 knockout mutants exhibit smaller mitochondria and defects in mitochondrial fusion under hypoxic stress. We further demonstrated that PMF1’s N-terminal domain is both necessary and sufficient to promote fusion in vivo. Notably, this domain contains extensive intrinsically disordered regions capable of mediating liquid-liquid phase separation in vitro. Fusion of PMF1’s N-terminal domain to a different mitochondrial membrane protein was sufficient to drive mitochondrial membrane fusion, suggesting that PMF1 condensation represents a novel mechanistic paradigm for mitochondrial fusion.
This SPUR project aims to further investigate the cellular and molecular mechanisms by which PMF1 promotes mitochondrial fusion. Specifically, we will examine how PMF1 regulates the initiation of fusion and how this process is influenced by mitochondrial energy production. We will confirm the interaction between PMF1’s evolutionarily conserved C-terminal domain and a mitochondrial ATP/ADP ratio-sensing protein and explore how this interaction directs mitochondrial fusion to optimize energy balance and production.
Undergraduate students involved in this project will generate fluorescence markers in the wild type and pmf1 mutant plants to characterize the mutant defects in mitochondrial morphology and energy production in transgenic plants. Also, the student will have the opportunity to explore the cell biology and biochemical activity of PMF1 protein and use genetic tools to dissect the PMF1’s position in the mitochondrial fusion pathway. Through this project, the student will learn essential molecular and cellular techniques used in modern biological research, including molecular cloning, fluorescence imaging, and immunoblotting. They will also learn various plant biology research tools, including plant gene cloning, transient heterologous expression, and generation of transgenic plants.
Students with strong interests in plant biology, cell biology and genetics will find the experience most rewarding. Excellent attention to detail and good record-keeping skills are necessary.