Managing the dark:light transition by dynamic micro-compartmentalization in plant mitochondria

• Applicants: Dr. Holger Eubel; Professor Alisdair Fernie, Ph.D., since 2/2018
• Subject Area: Plant Physiology
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 289286676

Mitochondria are common to all complex life. They host respiration as the source of the large amounts of ATP that are necessary to fuel energy-demanding cellular processes allowing movement, growth, and development. In plants, however, this situation changes with sunrise. Then photosynthesis takes over from respiration as the dominating bioenergetic process, and the physiological environment in which the mitochondria operate undergoes a profound transition. Photosynthesis drastically alters the cellular metabolite and cofactor pools and increases local oxygen levels. The mitochondrial machinery then not only sustains an altered cellular status, but supports efficient photosynthesis. This requires active re-dedication of mitochondrial function and implies strict coordination of the mitochondria with the chloroplasts. Moreover, it includes a periodic operational transition between light and dark that is unique to plants. In the proposed research, we will address the question how the rapid acclimation of mitochondrial functions during dark-to-light transitions is choreographed in green plant tissues by analysing the dynamics of protein:protein interactions at dawn. Association of enzymes to protein complexes leads to the formation of micro-compartments with reduced diffusion distances and increases turnover rates of pathways. It also limits losses of intermediates by branching or competing reactions and, as such, increases metabolic efficiency of pathways. For mammalian and yeast mitochondria protein:protein interactions of matrix enzymes with potential implications for regulation have already been shown. Similar interactions in plants were detected in a previous study. To assess to which extent dynamic protein:protein interactions impact on the adjustment of plant mitochondrial metabolism at dawn, we here propose a combination of biochemical and genetic approaches which enables a broad, yet (in parts) detailed view on this topic. Functional assays will be used to gain insight into the metabolic state of mitochondria before and after dawn and will enable direct correlation of changes in protein:protein interaction patterns with alterations of the physiological status of the mitochondria.Together with two other projects proposed as part of the Plant Mitochondria in a New Light initiative, this research will provide novel depth of insight into the mechanisms regulating mitochondrial function in photosynthetic organisms.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Toshihiro Obata, Ph.D., until 2/2018