mtsf1 mutants accumulate a truncated form of respiratory complex I. (A) Blue native PAGE gel analysis of the different respiratory complexes present in wild-type (Col-0) and mtsf1 mutant plants. About 200 µg of digitonin-treated mitochondrial proteins were loaded in each lane. After electrophoresis, the gel was stained with Coomassie blue to reveal the different respiratory complexes, which are identified by their roman numeral in the figure. Numbers on the right-hand side indicate positions of bands corresponding to molecular weight marker (in kDa) (B) In-gel staining revealing complex I activity in both wild-type (Col-0) and mtsf1 mutant plants. Gel running conditions were identical to that presented in panel A Sub I corresponds to the truncated form of complex I detected in mtsf1 mutants.