Pan R, Kaur N, Hu J

Mitochondria are essential organelles with dynamic morphology and function. Post-translational modifications (PTMs), including protein ubiquitination, are critically involved in animal and yeast mitochondrial dynamics. How PTMs contribute to plant mitochondrial dynamics is just beginning to be elucidated, and mitochondrial enzymes involved in ubiquitination have not been reported from plants. In ...

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this study, we identified an Arabidopsis mitochondrial localized ubiquitin protease, UBP27, through a screen combining bioinformatics and fluorescent fusion protein targeting analysis. We characterized UBP27 with respect to its membrane topology and enzymatic activities, and analyzed the mitochondrial morphological changes in UBP27 T-DNA insertion mutants and overexpression lines. We have shown that UBP27 is embedded in the mitochondrial outer membrane with an Nin -Cout orientation and possesses ubiquitin protease activities in vitro. UBP27 demonstrates similar subcellular localization, domain structure, membrane topology and enzymatic activities with two mitochondrial deubiquitinases, yeast ScUBP16 and human HsUSP30, indicating that these proteins are functional orthologs in eukaryotes. Although loss-of-function mutants of UBP27 do not show obvious phenotypes in plant growth and mitochondrial morphology, UBP27 overexpression can change mitochondrial morphology from rod to spherical shape and reduce the mitochondrial association of dynamin-related protein 3 (DRP3) proteins, large GTPases that serve as the main mitochondrial fission factors. Thus, our study has uncovered a plant ubiquitin protease that plays a role in mitochondrial morphogenesis possibly through modulation of the function of organelle division proteins.

Date: Apr. 07, 2014

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