Cadmium induces GAPDH- and- MDH mediated delayed cell aging and dysfunction in Candida tropicalis 3Aer

FonTup1 functions in growth, conidiogenesis and pathogenicity of Fusarium oxysporum f. sp. niveum through modulating the expression of the tricarboxylic acid cycle genes

The Tup1-Cyc8 complex is a highly conserved transcriptional corepressor that regulates intricate genetic network associated with various biological processes in fungi. Here, we report the role and mechanism of FonTup1 in regulating physiological processes and pathogenicity in watermelon Fusarium wilt fungus, Fusarium oxysporum f. sp. niveum (Fon). FonTup1 deletion impairs mycelial growth, asexual reproduction, and macroconidia morphology, but not macroconidial germination in Fon. The ΔFontup1 mutant exhibits altered tolerance to cell wall perturbing agent (congo red) and osmotic stressors (sorbitol or NaCl), but unchanged sensitivity to paraquat. The deletion of FonTup1 significantly decreases the pathogenicity of Fon toward watermelon plants through attenuating the ability to colonize and grow within the host. Transcriptome analysis revealed that FonTup1 regulates primary metabolic pathways, including the tricarboxylic acid (TCA) cycle, via altering the expression of corresponding genes. Downregulation of three malate dehydrogenase genes, FonMDH1-3, occurs in ΔFontup1, and disruption of FonMDH2 causes significant abnormalities in mycelial growth, conidiation, and virulence of Fon. These findings demonstrate that FonTup1, as a global transcriptional corepressor, plays crucial roles in different biological processes and pathogenicity of Fon through regulating various primary metabolic processes, including the TCA cycle. This study highlights the importance and molecular mechanism of the Tup1-Cyc8 complex in multiple basic biological processes and pathogenicity of phytopathogenic fungi.

Central Metabolism in Mammals and Plants as a Hub for Controlling Cell Fate

Significance: The importance of oxidoreductases in energy metabolism together with the occurrence of enzymes of central metabolism in the nucleus gave rise to the active research field aiming to understand moonlighting enzymes that undergo post-translational modifications (PTMs) before carrying out new tasks. Recent Advances: Cytosolic enzymes were shown to induce gene transcription after PTM and concomitant translocation to the nucleus. Changed properties of the oxidized forms of cytosolic glyceraldehyde 3-phosphate dehydrogenase, and also malate dehydrogenases and others, are the basis for a hypothesis suggesting moonlighting functions that directly link energy metabolism to adaptive responses required for maintenance of redox-homeostasis in all eukaryotes. Critical Issues: Small molecules, such as metabolic intermediates, coenzymes, or reduced glutathione, were shown to fine-tune the redox switches, interlinking redox state, metabolism, and induction of new functions via nuclear gene expression. The cytosol with its metabolic enzymes connecting energy fluxes between the various cell compartments can be seen as a hub for redox signaling, integrating the different signals for graded and directed responses in stressful situations. Future Directions: Enzymes of central metabolism were shown to interact with p53 or the assumed plant homologue suppressor of gamma response 1 (SOG1), an NAM, ATAF, and CUC transcription factor involved in the stress response upon ultraviolet exposure. Metabolic enzymes serve as sensors for imbalances, their inhibition leading to changed energy metabolism, and the adoption of transcriptional coactivator activities. Depending on the intensity of the impact, rerouting of energy metabolism, proliferation, DNA repair, cell cycle arrest, immune responses, or cell death will be induced. Antioxid. Redox Signal. 34, 1025-1047.

Three cytosolic NAD-malate dehydrogenase isoforms of Arabidopsis thaliana: on the crossroad between energy fluxes and redox signaling

In yeast and animal cells, mitochondrial disturbances resulting from imbalances in the respiratory chain require malate dehydrogenase (MDH) activities for re-directing fluxes of reducing equivalents. In plants, in addition to mitochondria, plastids use malate valves to counterbalance and maintain redox-homeostasis. Arabidopsis expresses three cytosolic MDH isoforms, namely cyMDH1, cyMDH2, and cyMDH3, the latter possessing an N-terminal extension carrying a unique cysteine residue C2. In this study, redox-effects on activity and structure of all three cyMDH isoforms were analyzed in vitro. cyMDH1 and cyMDH2 were reversibly inactivated by diamide treatment, accompanied by dimerization via disulfide-bridge formation. In contrast, cyMDH3 forms dimers and higher oligomers upon oxidation, but its low specific activity is redox-independent. In the presence of glutathione, cyMDH1 and cyMDH2 are protected from dimerization and inactivation. In contrast, cyMDH3 still dimerizes but does not form oligomers any longer. From analyses of single and double cysteine mutants and structural modeling of cyMDH3, we conclude that the presence of C2 and C336 allows for multiple cross-links in the higher molecular mass complexes comprising disulfides within the dimer as well as between monomers of two different dimers. Furthermore, nuclear localization of cyMDH isoforms was significantly increased under oxidizing conditions in isolated Arabidopsis protoplasts, in particular of isoform cyMDH3. The unique cyMDH3 C2-C2-linked dimer is, therefore, a good candidate as a redox-sensor taking over moonlighting functions upon disturbances of energy metabolism, as shown previously for the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) where oxidative modification of the sensitive catalytic cysteine residues induces nuclear translocation.