Biology subjects

Möhlmann, T.

Publications and source records attributed to Möhlmann, T..

3 recordsLinked to original sources

bioRxiv2026

A tonoplast cytokinin riboside transporter gates intracellular hormone availability at the plant-microbe interface

Cytokinin ribosides are major mobile and precursor forms of cytokinins, plant hormones whose transport and subcellular distribution shape developmental and stress responses. Here, we identify Arabidopsis thaliana EQUILIBRATIVE NUCLEOSIDE TRANSPORTER1 (ENT1) as a tonoplast-localized cytokinin riboside transporter. Tissue-specific subcellular analysis under native regulatory elements localized ENT1 predominantly to the tonoplast of root epidermal and lateral root cap cells, where it gates intracellular cytokinin riboside availability. Accordingly, ENT1 overexpression enhanced cytokinin riboside sensitivity and signalling, whereas loss of ENT1 altered adenosine metabolism and disrupted cytokinin homeostasis, leading to the accumulation of multiple zeatin-type cytokinins. ENT1-dependent cytokinin riboside compartmentalization was required for beneficial microbe-induced protection, as ent1 mutants failed to acquire protection against the fungal pathogen Botrytis cinerea and the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. These findings reveal a vacuolar gatekeeping mechanism that controls intracellular cytokinin riboside availability and links hormone compartmentalization to beneficial microbe-dependent plant defence.

plant biology↗

bioRxiv2023

UPP affects chloroplast development by interfering with chloroplast proteostasis

Arabidopsis uracil phosphoribosyltransferase (UPP) is an essential enzyme which appears to have a previously unknown, moonlighting activity. Our analysis of UPP amiRNA mutants has confirmed that this vital function is crucial for chloroplast development and growth. Interestingly, this function appears to be unrelated to nucleotide homeostasis since nucleotide levels were not altered in the studied mutants. Transcriptomics and proteomic analysis suggest that UPP plays a role in chloroplast proteostasis, especially under high light (HL). Immunoblots of mature plants and a de-etiolation experiment with young seedlings revealed PetC, the iron-sulfur protein of the cytochrome b6f complex, as a putative UPP target. In addition, UPP and PetC were identified in a high molecular weight complex. Consistently, we show that PetC is massively reduced in UPP knock-down plants. The block observed in photosynthetic electron transport, as evidenced by reduced high light-induced non-photochemical quenching (NPQ) but increased unregulated energy dissipation (NO), might be therefore a consequence of reduced PetC. After HL treatment, UPP amiRNA mutants showed impaired photosynthesis and reduced carbohydrate contents, resulting in an inability to induce flavonoid biosynthesis. In addition, the levels of the osmoprotectants raffinose, proline and fumarate were found to be reduced. Proteases, including thylakoid filamentation temperature-sensitive 1, 5 (FtsH), caseinolytic protease proteolytic subunit 1 (ClpP1), and processing peptidases, as well as components of the chloroplast protein import machinery, were up-regulated. In sum, our work suggests that UPP assists in stabilizing and protection of PetC during the assembly of the Fe-S cluster and targeting to the thylakoid.

molecular biology↗

bioRxiv2021

Pyrimidine nucleotide availability is essential for efficient photosynthesis, ROS scavenging, and organelle development

Nucleotide limitation and imbalance is a well described phenomenon in animal research but understudied in the plant field. A peculiarity of pyrimidine de novo synthesis in plants is the complex subcellular organization. Here, we studied two organellar localized enzymes in the pathway, with chloroplast aspartate transcarbamoylase (ATC), and mitochondrial dihydroorotate dehydrogenase (DHODH). ATC knockdowns were most severely affected, exhibiting low levels of pyrimidine nucleotides, a low energy state, reduced photosynthetic capacity and accumulation of reactive oxygen species (ROS). Furthermore, altered leaf morphology and chloroplast ultrastructure were observed in ATC mutants. Although less affected, DHODH knockdown mutants showed impaired seed germination and altered mitochondrial ultrastructure. Transcriptome analysis of an ATC-amiRNA line revealed massive alterations in gene expression with central metabolic pathways being downregulated and stress response and RNA related pathways being upregulated. In addition, genes involved in central carbon metabolism, intracellular transport and respiration were mainly downregulated in ATC mutants, being putatively responsible for the observed impaired growth. ONE-SENTENCE SUMMARYImpaired pyrimidine nucleotide synthesis results in nucleotide limitation and imbalance, resulting in impaired photosynthesis, reduced growth, reproduction, and seed yield together with massively altered gene expression

plant biology↗