The seed mitochondrial proteome of Lupinus albus provides insight into energy metabolism during germination

Despite their essential role in fueling the onset of metabolism, the composition and functional state of seed mitochondria are still a matter of debate. Using white lupin (Lupinus albus) as a model, we provide a comprehensive proteomic characterization of seed mitochondria in a legume with protein-rich reserves. Highly enriched mitochondrial fractions isolated from quiescent seeds revealed fully assembled oxidative phosphorylation (OXPHOS) complexes and supercomplexes, demonstrating that mitochondria are preconfigured for immediate energy production upon imbibition. Quantitative proteomics identified 1,162 mitochondrial proteins and highlighted marked tissue-specific differences compared to leaves, including distinct transporter profiles and a dehydrogenase complement supporting amino acid and fatty acid catabolism. Early germination was accompanied by remodeling of coenzyme metabolism and transport capacity, while core respiratory complexes remained stable. Notably, [~]12% of the proteome consisted of uncharacterized proteins, many of which displayed dynamic changes during early germination, suggesting yet undiscovered, potentially legume-specific mitochondrial functions.