Miro2 tethers the ER to mitochondria to promote mitochondrial fusion in tobacco leaf epidermal cells

Abstract

Mitochondria are essential for energy conversion, and metabolic pathways including photorespiration, biosynthesis of coenzymes and vitamins. They are highly pleomorphic undergoing rounds of fission and fusion through processes coupled with the metabolic status of the cell. For example, fusion favours higher energy demand and, unlike fission, the molecular components involved in mitochondrial fusion in plants are unknown. Here, we show a role for the GTPase Miro2 in mitochondria interaction with the ER and its impacts on mitochondria fusion and motility. Interaction between these two organelles has been inferred from close positioning. Mutations in AtMiro2’s GTPase domain indicate that the active variant results in larger, fewer mitochondria which are attached more readily to the ER when compared with the inactive variant. These results are contrary to those in metazoans where Miro predominantly controls mitochondrial motility with additional GTPases affecting fusion. Synthetically controlling mitochondrial fusion rates could fundamentally change plant physiology by altering the energy status of the cell. Furthermore, altering tethering to the ER could have profound effects on subcellular communication through altering the exchange required for pathogen defence.