Title: Alternative oxidase and ethylene form a positive feed-forward loop in mitochondrial retrograde signalling.
Cunman He, Reena Narsai, Lim Chee Liew, Yan Zhang, Lingling Yin, Juan Xu, Mingtang Xie, Huixia Shou, Joseph R. Ecker, Mathew G. Lewsey, Yong Wang, Oliver Berkowitz, James Whelan*
Abstract
To dissect the ANAC017 mitochondrial retrograde signalling pathway we identified 2-oxoglutarate and Fe(II)-dependent oxygenase (OGO) as being induced by perturbation of mitochondrial function with antimycin A (AA), but not by high light. A forward genetic screen was implemented using the promoter region of 2-oxoglutarate and Fe(II)-dependent oxygenase (OGO) fused to firefly luciferase to identify regulators of OGO, in order to identify regulators of mitochondrial perturbation, distinct from those that also impact chloroplast function. A mutant termed ROG1 (Regulators of OGO) was identified as encoding mitochondrial Alternative Oxidase 1a (AOX1a). To understand how AOX1a affects OGO expression we investigated ethylene production in rog1(aox1a) mutant lines and found it was significantly reduced. Importantly ethylene production could be restored by the expression of AOX1c, indicating that it was Alternative Oxidase activity in general that was required for ethylene production, not specifically AOX1a activity. Ethylene production was also constitutively induced in ANAC017 over-expression lines. Metabolite profiling of aox1a lines treated with AA revealed a large perturbation of folate, methionine and ascorbate glutathione cycle metabolites, significant reduction of ATP and ADP, and alterations of the NAD(P)H: NAD(P) ratio. Combined these results reveal a central role for AOX in maintaining hormone production and REDOX balance under mitochondrial perturbation linked to key metabolites that have been characterised as playing key roles in response to abiotic challenge. It also positions AOX as an essential component required for a variety of abiotic and biotic stress responses.
Link: https://www.cell.com/plant-communications/fulltext/S2590-3462(26)00052-0
