The mitochondrial proteome of the moss Physcomitrella patens

- The moss Physcomitrella is an important plant model species for cell biology.
- It facilitates evolutionary comparisons of protein compartmentation.
- Differences in plant mitochondrial functions and their regulation do exist.
- Metabolic labelling and gene editing facilitate gene/function correlations.
- Mitochondrial protein stability may be regulated by the cytosolic N-end rule pathway.

Extant basal land plants are routinely used to trace plant evolution and to track strategies for high abiotic stress resistance. Whereas the structure of mitochondrial genomes and RNA editing are already well studied, mitochondrial proteome research is restricted to a few data sets. While the mitochondrial proteome of the model moss Physcomitrella patens is covered to an estimated 15-25% by proteomic evidence to date, the available data have already provided insights into the evolution of metabolic compartmentation, dual targeting and mitochondrial heterogeneity. This review summarizes the current knowledge about the mitochondrial proteome of P. patens, and gives a perspective on its use as a mitochondrial model system. Its amenability to gene editing, metabolic labelling as well as fluorescence microscopy provides a unique platform to study open questions in mitochondrial biology, such as regulation of protein stability, responses to stress and connectivity to other organelles. Future challenges will include improving the proteomic resources for P. patens, and to link protein inventories and modifications as well as evolutionary differences to the functional level.