ACONITASE 3 is part of theANAC017 transcription factor-dependent mitochondrial dysfunction response.

Jesús Pascual,Alexey Shapiguzov,Zsófia Winter,Sara Alegre,Jari Sinkkonen,Guido Durian,Richard Gossens,Moona Rahikainen,Jaakko Kangasjärvi,James Whelan,Andrea Trotta,Arttu Heinonen,Saijaliisa Kangasjärvi,Martina Angeleri

doi:10.1093/plphys/kiab225

Abstract

Mitochondria are tightly embedded within metabolic and regulatory networks that optimize plant performance in response to environmental challenges. The best-known mitochondrial retrograde signaling pathway involves stress-induced activation of the transcription factor NAC DOMAIN CONTAINING PROTEIN 17 (ANAC017), which initiates protective responses to stress-induced mitochondrial dysfunction in Arabidopsis (Arabidopsis thaliana). Posttranslational control of the elicited responses, however, remains poorly understood. Previous studies linked protein phosphatase 2A subunit PP2A-B’γ, a key negative regulator of stress responses, with reversible phosphorylation of ACONITASE 3 (ACO3). Here we report on ACO3 and its phosphorylation at Ser91 as key components of stress regulation that are induced by mitochondrial dysfunction. Targeted mass spectrometry-based proteomics revealed that the abundance and phosphorylation of ACO3 increased under stress, which required signaling through ANAC017. Phosphomimetic mutation at ACO3-Ser91 and accumulation of ACO3S91D-YFP promoted the expression of genes related to mitochondrial dysfunction. Furthermore, ACO3 contributed to plant tolerance against ultraviolet B (UV-B) or antimycin A-induced mitochondrial dysfunction. These findings demonstrate that ACO3 is both a target and mediator of mitochondrial dysfunction signaling, and critical for achieving stress tolerance in Arabidopsis leaves.

Highlights

Plants respond to environmental stimuli by metabolic adjustments that enable growth and survival when biotic and abiotic challenges occur
ACONITASE 3 (ACO3) phosphomutant lines do not display visual phenotypes in the absence of stress To investigate the physiological role of ACO3 phosphorylation at Ser91, we complemented Arabidopsis aco3 knockout mutant with the ACO3 coding sequence in
ACO3-yellow fluorescent protein (YFP), ACO3S91AYFP, and ACO3S91D-YFP were imaged in leaves excised from 4-week-old plants, using Mitotracker to compare the localization of ACO3 variants to the localization pattern of mitochondria (Figure 2A)

Summary

Introduction

Plants respond to environmental stimuli by metabolic adjustments that enable growth and survival when biotic and abiotic challenges occur. Stress-induced disruption of metabolic reactions can cause accumulation of metabolic intermediates and reactive oxygen species (ROS), which serve well-documented signaling functions in stressexposed tissues (Obata and Fernie, 2012; Foyer et al, 2017; Waszczak et al, 2018). Dysfunctional mitochondria communicate through retrograde signaling pathways, which alter the expression of nuclear genes with consequent readjustments in cellular redox balance, metabolism, and detoxification (Ho et al, 2008; Van Aken and Whelan, 2012; De Clercq et al, 2013; Ng et al, 2013). MDR can, be elicited by environmental, pharmacological, and genetic perturbations, such as plant exposure to the mitochondrial complex III inhibitor antimycin A (AA) or UV-B irradiation, which trigger partially overlapping transcriptional responses (Umbach et al, 2012; Willems et al, 2016)

Methods

Results

Conclusion