The conditional mitochondrial protein complexome in the Arabidopsis thaliana root and shoot.

Protein complexes are important for almost all biological processes. Hence, to fully understand how cells work, it is also necessary to characterize protein complexes and their dynamics in response to various cellular cues. Moreover, the dynamics of protein interaction play crucial roles in regulating the (dis)association of protein complexes and, in turn, regulating biological processes such as metabolism. Here, mitochondrial protein complexes were investigated by blue native PAGE and size-exclusion chromatography under conditions of oxidative stress in order to monitor their dynamic (dis)associations. Rearrangements of enzyme interactions and changes in protein complex abundance were observed in response to oxidative stress induced by menadione treatment. These included changes in enzymatic protein complexes involving γ-amino butyric acid transaminase (GABA-T), Δ-ornithine aminotransferase (Δ-OAT), or proline dehydrogenase 1 (POX1) that are expected to affect proline metabolism. Menadione treatment also affected interactions between several enzymes of the tricarboxylic acid (TCA) cycle and the abundance of complexes of the oxidative phosphorylation pathway. In addition, we compared the mitochondrial complexes of roots and shoots. Considerable differences between the two tissues were observed in the mitochondrial import/export apparatus, the formation of super-complexes in the oxidative phosphorylation pathway, and specific interactions between enzymes of the TCA cycle that we postulate may be related to the metabolic/energetic requirements of roots and shoots.