Mitochondrial Pyruvate Carriers Prevent Cadmium Toxicity by Sustaining the TCA Cycle and Glutathione Synthesis

Abstract

Cadmium (Cd) is a major heavy metal pollutant, and Cd toxicity is a serious cause of abiotic stress in the environment. Plants protect themselves against Cd stress through a variety of pathways. In a recent study, we found that mitochondrial pyruvate carriers (MPCs) are involved in Cd tolerance in Arabidopsis (Arabidopsis thaliana). Following the identification of MPCs in yeast (Saccharomyces cerevisiae) in 2012, most studies have focused on the function of MPCs in animals, as a possible approach to reduce the risk of cancer developing. The results of this study show that AtMPC protein complexes are required for Cd tolerance and prevention of Cd accumulation in Arabidopsis. AtMPC complexes are composed of two elements, AtMPC1 and AtMPC2 (AtNRGA1 or AtMPC3). When the formation of AtMPCs was interrupted by the loss of AtMPC1, glutamate could supplement the synthesis of acetyl-coenzyme A and sustain the TCA cycle. With the up-regulation of glutathione synthesis following exposure to Cd stress, the supplementary pathway could not efficiently drive the tricarboxylic acid cycle without AtMPC. The ATP content decreased concomitantly with the deletion of tricarboxylic acid activity, which led to Cd accumulation in Arabidopsis. More importantly, ScMPCs were also required for Cd tolerance in yeast. Our results suggest that the mechanism of Cd tolerance may be similar in other species.

Genetic Dissection of the Seminal Root System Architecture in Mediterranean Durum Wheat Landraces by Genome-Wide Association Study

“…Zhang et al [52] observed that the root growth of transgenic plants overexpressing the gene TabZIP14-B was hindered more severely than that of the control plants. Another gene involved in abiotic stress tolerance is the mitochondrial pyruvate carrier (MPC) located in mtaq-7A.1 [53]. This gene is involved in cadmium tolerance in Arabidopsis, which prevents its accumulation.…”

“…Roots are the predominant plant tissue for cadmium absorption or exclusion. He et al [53] found that the root length of mutant plants of Arabidopsis for MPC genes was substantially shorter than the wild-type plants. A protein related to WAT1 (WALLS ARE THIN1) involved in secondary cell wall thickness [54] is located in the peak of mtaq-7A.1.…”

The Arabidopsis mitochondrial dicarboxylate carrier 2 maintains leaf metabolic homeostasis by uniting malate import and citrate export

“…A null mutant of mitochondrial citrate synthase has not been reported to date, and a reduction in mitochondrial citrate synthase activity only resulted in a small change in vegetative growth phenotype (21, 22). Unlike in yeast and mammals, the function of plant mitochondrial pyruvate carrier (MPC) seems to be non-essential since its absence has no effect on growth or the cellular citrate pool (16, 68). In comparison, mutants lacking the activity in one of the subunits of mitochondrial pyruvate dehydrogenase complex (mPDC) or both mMDH isoforms, which catalyse acetyl-CoA and OAA formation respectively required for citrate synthesis, are significantly slower in vegetative growth (23, 69, 70).…”

Enhanced pyruvate metabolism in plastids by overexpression of putative plastidial pyruvate transporter in Phaeodactylum tricornutum

“…Pyruvate is a central intermediate associated with many metabolic pathways, including the TCA cycle, glycolysis [28,29], biosynthesis of amino acids [30], terpenoids [31], and de novo fatty acids [28,29]. However, pyruvate transporters that deliver pyruvate to mitochondria or plastids have been only identi ed in yeast, drosophila, mammalian cells, and plants [32][33][34][35]. Plastidial pyruvate transporters, especially in plants, are characterized by their function [35].…”