Examinando por Autor "Kraemer, Ute"

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Energy status-promoted growth and development of Arabidopsis require copper deficiency response transcriptional regulator SPL7
(Oxford University Press, 2022-07-22) Schulten, Anna; Pietzenuk, Bjoern; Quintana, Julia; Scholle, Marleen; Feil, Regina; Krause, Markus; Romera-Branchat, Maida; Wahl, Vanessa; Severing, Edouard; Coupland, George; Kraemer, Ute
Copper (Cu) is a cofactor of around 300 Arabidopsis proteins, including photosynthetic and mitochondrial electron transfer chain enzymes critical for adenosine triphosphate (ATP) production and carbon fixation. Plant acclimation to Cu deficiency requires the transcription factor SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE7 (SPL7). We report that in the wild type (WT) and in the spl7-1 mutant, respiratory electron flux via Cu-dependent cytochrome c oxidase is unaffected under both normal and low-Cu cultivation conditions. Supplementing Cu-deficient medium with exogenous sugar stimulated growth of the WT, but not of spl7 mutants. Instead, these mutants accumulated carbohydrates, including the signaling sugar trehalose 6-phosphate, as well as ATP and NADH, even under normal Cu supply and without sugar supplementation. Delayed spl7-1 development was in agreement with its attenuated sugar responsiveness. Functional TARGET OF RAPAMYCIN and SNF1-RELATED KINASE1 signaling in spl7-1 argued against fundamental defects in these energy-signaling hubs. Sequencing of chromatin immunoprecipitates combined with transcriptome profiling identified direct targets of SPL7-mediated positive regulation, including Fe SUPEROXIDE DISMUTASE1 (FSD1), COPPER-DEFICIENCY-INDUCED TRANSCRIPTION FACTOR1 (CITF1), and the uncharacterized bHLH23 (CITF2), as well as an enriched upstream GTACTRC motif. In summary, transducing energy availability into growth and reproductive development requires the function of SPL7. Our results could help increase crop yields, especially on Cu-deficient soils.
Root‐to‐shoot iron partitioning in Arabidopsis requires IRON‐REGULATED TRANSPORTER1 (IRT1) protein but not its iron(II) transport function
(Wiley, 2022) Quintana, Julia; Bernal, María; Scholle Marleen; Holländer‐Czytko, Heike; Nga, Nguyen T.; Piotrowski, Markus; Mendoza‐Cózatl, David G.; Haydon, Michael J.; Kraemer, Ute
IRON‐REGULATED TRANSPORTER1 (IRT1) is the root high‐affinity ferrous iron uptake system and indispensable for the completion of the life cycle of Arabidopsis thaliana without vigorous iron (Fe) supplementation. Here we provide evidence supporting a second role of IRT1 in root‐to‐shoot partitioning of Fe. We show that irt1 mutants over‐accumulate Fe in roots, most prominently in the cortex of the differentiation zone in irt1‐2, compared to the wild type. Shoots of irt1‐2 are severely Fe‐deficient according to Fe content and marker transcripts, as expected. We generated irt1‐2 lines producing IRT1 mutant variants carrying single amino‐acid substitutions of key residues in transmembrane helices IV and V, Ser206 and His232, which are required for transport activity in yeast. Root short‐term 55Fe uptake rates were uninformative concerning IRT1‐mediated transport. Overall irt1‐like concentrations of the secondary substrate Mn suggested that the transgenic Arabidopsis lines also remain incapable of IRT1‐mediated root Fe uptake. Yet, IRT1S206A partially complements rosette dwarfing and leaf chlorosis, as well as root‐to‐shoot Fe partitioning and gene expression defects of irt1‐2, all of which are fully complemented by wild‐type IRT1. Taken together, these results suggest a function for IRT1 in root‐to‐shoot Fe partitioning that does not require Fe transport activity of IRT1. Among the genes of which transcript levels are partially dependent on IRT1, we identify MYB DOMAIN PROTEIN10, MYB DOMAIN PROTEIN72 and NICOTIANAMINE SYNTHASE4 as candidates for effecting IRT1‐dependent Fe mobilization in roots. Understanding the biological functions of IRT1 will help to improve iron nutrition and the nutritional quality of agricultural crops.
Translational fidelity and growth of Arabidopsis require stress-sensitive diphthamide biosynthesis
(Springer Nature, 2022) Zhang, Hongliang; Quintana, Julia; Ütkür, Koray; Adrian, Lorenz; Hawer, Harmen; Mayer, Klaus; Gong, Xiaodi; Castanedo, Leonardo; Schulten, Anna; Janina, Nadežda; Peters, Marcus; Wirtz, Markus; Brinkmann, Ulrich; Schaffrath, Raffael; Kraemer, Ute
Diphthamide, a post-translationally modified histidine residue of eukaryotic TRANSLATION ELONGATION FACTOR2 (eEF2), is the human host cell-sensitizing target of diphtheria toxin. Diphthamide biosynthesis depends on the 4Fe-4S-cluster protein Dph1 catalyzing the first committed step, as well as Dph2 to Dph7, in yeast and mammals. Here we show that diphthamide modification of eEF2 is conserved in Arabidopsis thaliana and requires AtDPH1. Ribosomal −1 frameshifting-error rates are increased in Arabidopsis dph1 mutants, similar to yeast and mice. Compared to the wild type, shorter roots and smaller rosettes of dph1 mutants result from fewer formed cells. TARGET OF RAPAMYCIN (TOR) kinase activity is attenuated, and autophagy is activated, in dph1 mutants. Under abiotic stress diphthamide-unmodified eEF2 accumulates in wild-type seedlings, most strongly upon heavy metal excess, which is conserved in human cells. In summary, our results suggest that diphthamide contributes to the functionality of the translational machinery monitored by plants to regulate growth. Diphthamide is a post-translationally modified histidine residue present in animal and yeast TRANSLATION ELONGATION FACTOR2. Here the authors show that diphthamide modification of eEF2 is conserved in Arabidopsis thaliana and contributes to translational fidelity and growth via cell proliferation.