Mitochondrial ATP Synthase Subunit d, a Component of the Peripheral Stalk, is Essential for Growth and Heat Stress Tolerance inArabidopsis thaliana

Abstract

As rapid changes in climate threaten global crop yields, an understanding of plant heat stress tolerance is increasingly relevant. Heat stress tolerance involves the coordinated action of many cellular processes and is particularly energy demanding. We acquired a knockout mutant and generated knockdown lines in Arabidopsis thaliana of the d subunit of mitochondrial ATP synthase (gene name: ATPQ, AT3G52300, referred to hereafter as ATPd), a subunit of the peripheral stalk, and used these to investigate the phenotypic significance of this subunit in normal growth and heat stress tolerance. Homozygous knockout mutants for ATPd could not be obtained due to gametophytic defects, while heterozygotes possess no visible phenotype. Therefore, we used RNAi to create knockdown plant lines for further studies. Proteomic analysis and blue native gels revealed that ATPd downregulation impairs only subunits of the mitochondrial ATP synthase (complex V of the electron transport chain). Knockdown plants were more sensitive to heat stress, had abnormal leaf morphology, and were severely slow growing compared to wild type. These results indicate that ATPd plays a crucial role in proper function of the mitochondrial ATP synthase holoenzyme, which, when reduced, leads to wide-ranging defects in energy-demanding cellular processes. In knockdown plants, more hydrogen peroxide accumulated and mitochondrial dysfunction stimulon (MDS) genes were activated. These data establish the essential structural role of ATPd and provide new information about complex V assembly and quality control, as well as support the importance of mitochondrial respiration in normal plant growth and heat stress tolerance.

mTERF18 and ATAD3 are required for mitochondrial nucleoid structure and their disruption confers heat tolerance in Arabidopsis thaliana

“…These changes are no doubt critical to the enhanced heat tolerance of shot1 . The fact that plants with compromised ATAD3A1 function also show disrupted nucleoids and enhanced heat tolerance suggests specific signaling of nucleoid status to the rest of the cell; other mutants defective in OXPHOS, such as the complex I mutant ndusf4 and complex V knockdown plants, are in fact rather heat sensitive (Kim et al ., 2012; Liu et al ., 2021), and as we show here an ndusf4 mutant has normal nucleoids. The connection between mitochondrial genome disruption and enhanced thermotolerance was previously reported in msh1 recA3 double mutants (Shedge et al ., 2010).…”