Biology subjects

Fürtauer, L.

Publications and source records attributed to Fürtauer, L..

4 recordsLinked to original sources

bioRxiv2024

Cytosolic fructose - an underestimated player in the regulation of the sucrose biosynthesis?

Plants must continuously adapt to environmental fluctuations, which significantly influence their photosynthetic performance and overall metabolism. The sucrose cycling system within plant cells plays a critical regulatory role during stress conditions. This study employed a systems biology approach to analyze system stabilities mathematically under various regulatory conditions impacting sucrose cycling dynamics. We investigated the effects of mutations within this cycle, specifically HEXOKINASE1 (Arabidopsis thaliana gin2-1), alongside high-light exposure. Finally, we confirmed the modelling output in vitro by enzyme assays. The implementation of experimental subcellular metabolite data into a Structural Kinetic Model (SKM) enabled exploration of regulatory responses and system stabilities within a three-compartment model. Within system instabilities, gin2-1 was more instable than its wild type. The gin2-1 mutation particularly was destabilized when fructokinase function was impaired by phosphorylated sugars. Additionally, we confirmed that phosphorylated sugars serve as stronger activators of sucrose-phosphate synthase (SPS) than glucose does. Interestingly, models with fructose SPS activation exhibited a similar stability pattern. Consequently, we proposed and confirmed in silico a triple activation of SPS by highly activating phosphorylated sugars and lower activating nonphosphorylated hexoses. Additionally, we biochemically confirmed the previously unknown, but now predicted, activation of SPS by fructose in vitro. In summary, our study highlights the essential role of sucrose cycling in plant cells under stress conditions. The in silico findings reveal that phosphorylated sugars are stronger activators of SPS than glucose and introduce a previously unknown activation mechanism by fructose. These potential activation capacities were confirmed in vitro through SPS enzyme activity assays, underscoring the efficiency of our systems biology approach. Overall, this research provides valuable insights into carbohydrate metabolism regulation and paves the way for future investigations to deepen our understanding of the complexities involved in sucrose cycling and biosynthesis in plants.

plant biology↗

bioRxiv2023

Marker and readout genes for priming in the Arabidopsis - Pseudomonas cannabina pv. alisalensis interaction

After a local infection, the entire plant foliage becomes primed for the superinduction of defense responses after rechallenge. The identity of genes expressed during priming (priming-marker genes) or with hyperexpression in primed plants after rechallenge (priming-readout genes) remained largely unknown. We show in Arabidopsis thaliana that genes AT1G76960 (with unknown function), AT3G51860 (encoding vacuolar Ca2+/H+ antiporter CAX3), and AT3G45860 (cysteine-rich receptor-like protein kinase CRK4) are strongly expressed during Pseudomonas cannabina pv. alisalensis-induced priming but not, or much less, in uninfected or challenged plants, or in primed plants after rechallenge. Expression of these genes thus solely marks the primed state for enhanced defense. In contrast to these genes, expression of AT2G14610 (pathogenesis-related protein PR1), AT2G32680 (receptor-like protein RLP23), AT3G25010 (RLP41) and some less expressed loci are activated, about equally, in primed plants before and after rechallenge. They may also serve as marker genes for priming. In further contrast, genes AT2G39530 (encoding Casparian strip domain-like protein 4D1), AT2G19190 (flg22-induced receptor-like kinase FRK1), AT3G28510 (P loop-containing nucleoside triphosphate hydrolases superfamily protein) and some less strongly expressed genes are not, or only faintly activated in uninfected plants, during priming and upon challenge. However, their expression is very strong in primed plants after rechallenge. They are, therefore, specific readout genes for the primed state. Remarkably, mutation in solely priming-readout gene AT5G36970 (encoding NDR1/HIN1-like protein 25) impaired both infection-induced defense priming and systemic acquired resistance suggesting a previously unknown critical role of this gene in the systemic plant immune response.

plant biology↗

bioRxiv2022

The vacuolar sugar transporter EARLY RESPONSE TO DEHYDRATION 6-LIKE4 regulates fructose signaling and plant growth

Regulation of intracellular sugar homeostasis is maintained by regulation of activities of sugar import and export proteins residing at the tonoplast. We show here that the EARLY RESPONSE TO DEHYDRATION6-LIKE4 protein, being the closest homolog to the proton/glucose symporter ERDL6, resides in the vacuolar membrane. Gene expression and subcellular fractionation studies indicated that ERDL4 was involved in fructose allocation across the tonoplast. Overexpression of ERDL4 increased total sugar levels in leaves, due to a concomitantly induced stimulation of TST2 expression, coding for the major vacuolar sugar loader. This conclusion is supported by the finding that tst1-2 knockout lines overexpressing ERDL4 lack increased cellular sugar levels. ERDL4 activity contributing to the coordination of cellular sugar homeostasis is also indicated by two further observations. Firstly, ERDL4 and TST genes exhibit an opposite regulation during a diurnal rhythm, and secondly, the ERDL4 gene is markedly expressed during cold acclimation representing a situation in which TST activity needs to be upregulated. Moreover, ERDL4-overexpressing plants show larger size of rosettes and roots, a delayed flowering time and increased total seed yield. Consistently, erdl4 knock-out plants show impaired cold acclimation and freezing tolerance along with reduced plant biomass. In summary, we show that modification of cytosolic fructose levels influences plant organ development and stress tolerance. One sentence summaryThe activity of the vacuolar sugar porter ERDL4 is important for balanced cytosolic monosaccharide homeostasis and influences plant growth and cold response in Arabidopsis The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors is: Benjamin Pommerrenig (pommerre@bio.uni-kl.de).

plant biology↗

bioRxiv2020

Vacuolar sucrose homeostasis is critical for development, seed properties and survival of dark phases of Arabidopsis

Although we know that most of the cellular sucrose is present in the cytosol and vacuole, our knowledge on the impact of this sucrose compartmentation on plant properties is still fragmentary. Here we attempted to alter the intracellular sucrose compartmentation of Arabidopsis mesophyll cells by either, overexpression of the vacuolar sucrose loader BvTST2.1 or by generation of mutants with decreased vacuolar invertase activity (amiR vi1-2). Surprisingly, BvTST2.1 overexpression led to increased monosaccharide levels in leaves, while sucrose remained constant. Latter observation allows the conclusion, that vacuolar invertase activity in mesophyll vacuoles exceeds sucrose uptake in Arabidopsis, which gained independent support by analyses on tobacco leaves transiently overexpressing BvTST2.1 and the invertase inhibitor NbVIF. However, we observed strongly increased sucrose levels in leaf extracts from independent amiR vi1-2 lines and non-aqueous fractionations confirmed that sucrose accumulation in corresponding vacuoles. amiR vi1-2 lines exhibited impaired early development and decreased weight of seeds. When germinated in the dark, mutant seedlings showed problems to convert sucrose into monosaccharides. Cold temperatures induced marked downregulation of the expression of both VI genes, while frost tolerance of amiR vi1-2 mutants was similar to WT indicating that increased vacuolar sucrose levels fully compensate for low monosaccharide concentrations. HighlightVacuolar sucrose accumulation in Arabidopsis is limited by high invertase activity and disturbed vacuolar sucrose homeostasis impairs plant germination, development, seed properties and survival under darkness.

plant biology↗